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Clarissa Willers, PhD

Postdoctoral Research Fellow, North-West University, Potchefstroom, South Africa

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Dr. Clarissa Willers is a Postdoctoral Research Fellow at Pharmacen™, Centre of Excellence for Pharmaceutical Sciences, at the North-West University in Potchefstroom, South Africa. She obtained her PhD in Environmental Sciences in 2016, with her main focus on soil microbiology. Dr. Willers is part of a research team that develops and uses cell culture models for pharmaceutical applications. Studies she is involved in focus on the bioavailability and permeability of drugs across membranes, the overall cytotoxicity of drugs and potential herb-drug interactions occurring when prescribed Western drugs are used in conjunction with traditional plant medicines. Moreover, traditional plant extracts with possible anti-cancerous and wound-healing effects also form part of her research. Although traditional two-dimensional (2D) cell culture models are routinely used, she and her colleagues are currently developing and establishing three-dimensional (3D) spheroid models as an improved representation of in vivo tumours for cancer drug resistance research. Dr. Willers has published eight publications in international peer-reviewed journals so far and her research has been presented at three international and three national conferences.

Learn about Clarissa’s research

Title: 3D spheroid cell models for drug-resistant cancer research

Learning objectives

  • To understand the use of three-dimensional micro-gravity spheroid cell models in cancer research, as an improvement on traditional two-dimensional cell cultures.
  • How to approach establishing and using 3D micro-gravity spheroid cell models for cancer research.
  • Exploring the potential applications of 3D micro-gravity spheroid cell models to investigate drug resistance in cancer.

The failure of current chemotherapeutic strategies in the fight against cancer can be largely attributed to the occurrence of drug resistance. Drug resistance is a major concern, especially in aggressive and highly metastatic tumours with a poor prognosis. In vitro cell-based models cultured as traditional two-dimensional (2D) cultures are commonly used for cancer research, including drug resistance studies. However, the inconsistencies between 2D in vitro results and in vivo or clinical findings have raised doubts about the accountability of 2D in vitro models as accurate representatives of in vivo tumours. Seeing as cancer cells cultured as three-dimensional (3D) spheroids have been shown to more closely mimic the complex microenvironment of an in vivo tumour, these models may overcome the aforementioned discrepancies. We aim to develop novel 3D micro-gravity spheroid-based cancer models to investigate drug resistance. This is done with different small cell lung cancer (SCLC) cell lines with varying levels of efflux transporters, which are known to be frequently involved in drug resistance mechanisms. Each of these models is validated through comparison of standard anticancer drug efficacy to published in vivo or clinical findings. Our main application of these models, currently, is investigating the potential of traditional herbal medicines to reduce or overcome efflux transporter-based drug resistance in SCLC.

Watch the webinar

Presenter:  Clarissa Willers, PhD

00:00 – Slide 1

Alexis Corrales:  Hello, everyone, and welcome to today’s live broadcast, 3D Spheroid Cell Models for Drug-Resistant Cancer Research, presented by Dr. Clarissa Willers, postdoctoral research fellow, Pharmacen Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom, South Africa.  I am Alexis Corrales of LabRoots and I’ll be your moderator for today’s event.

Today’s educational web seminar is brought to you by LabRoots and sponsored by Thermo Fisher Scientific.  For more information on our sponsor, please visit thermofisher.com.  Now let’s get started.  (00:37)

Before we begin, I would like to remind everyone that this event is interactive.  We encourage you to participate by submitting as many questions as you want at any time you want during the presentation.  To do so, simply type them into the Ask a Question box and click on the Send button.  We’ll answer as many questions as we have time for at the end of the presentation.  If you have trouble seeing or hearing the presentation, click on the Support tab found at the top right of the presentation window or report your problem by clicking on the Answer a Question box located on the far left of your screen.  (01:10)

This presentation is educational and thus offers continuing education credits.  Please click on the Continuing Education Credits tab located at the top right of the presentation window and follow the process to obtain your credits.  (01:24)

I’d like to now introduce our presenter, Dr. Clarissa Willers.  Dr. Clarissa Willers is a postdoctoral research fellow at Pharmacen Centre of Excellence for Pharmaceutical Sciences at the North-West University in South Africa.  She obtained her PhD in environmental sciences in 2016 with her main focus on soil microbiology.  Dr. Willers is a part of a research team that develops and uses cell culture models for pharmaceutical applications.  (01:52) She is involved in focusing on the bioavailability and permeability of drugs across the membranes, the overall cytotoxicity of drugs and potential herb-drug interactions occurring when prescribed Western drugs are used in conjunction with traditional plant medicines.  Moreover, traditional plant extracts with possible anticancerous and wound-healing effects also form part of her research.  For a complete biography on our speaker, please visit the Biography tab at the top of your screen.  (02:21)

Dr. Willers, you may now begin your presentation.

Clarissa Willers:  Thank you for that introduction.  Hi, I am Dr. Clarissa Willers and I am honored to be part of the Gibco Cell Culture Heroes campaign driven by Thermo Fisher Scientific.  I would like to thank Chelsea, Mikkel and (Kristi @ 02:46) for all their arrangements to make this webinar a success.

I am a postdoctoral researcher at the Potchefstroom Campus of the North-West University in South Africa.  At the Centre of Excellence for Pharmaceutical Sciences, our cell culture research focuses on developing novel mammalian cell culture models for applications in drug research, mainly traditional African medicine and the possible interactions with conventional medicine.  Side by side with our hosts, Dr. Chrisna Gouws and Prof. Sias Hamman, my colleague, Dr. Carlemi Calitz, and I are currently establishing three-dimensional cell culture models for multidrug-resistant cancer research.

03:41 – Slide 2

Traditional two-dimensional in vitro cell culture models are frequently used for anticancer drug research, seeing as such cultures are easy to maintain and monitor without the ethical restrictions associated with animal studies.  Nevertheless, numerous inconsistencies occur between 2D findings in comparison to in vivo and clinical trials.

04:11 – Slide 3

Discrepancies such as irregular cell morphology not similar to the original tumor tissue, as well as the inability among cells to communicate, and the failure to facilitate essential metabolic functions have been reported for cell cultures in 2D conditions.

04:37 – Slide 4

These inconsistencies may be related to the fact that cancer cells cultured in 2D allocate more of their resources into continuous cell proliferation than into important functional pathways.  Also, 2D cell cultures require artificial attachment surfaces for propagation, and constant subculturing for adequate nutrient and growth space.  This leads to concerns regarding the reliability and credibility of 2D in vitro models as accurate screening tools representative of in vivo cancer tissue.

05:22 – Slide 5

Conversely, cancer cells cultured as three-dimensional spheroid cultures have been found to more closely mimic the complex microenvironment of in vivo tumors.  These 3D cell spheroids develop intricate extracellular matrices and can execute intracellular communication, which enables physiological changes, making them more similar to their cancerous tissues of origin.  (05:55) Using the 3D spheroid-based model, the cells are no longer in an unrestrained exponential growth phase where proliferation is the main focus, but the 3D spheroids are allowed to reach a state of dynamic equilibrium where the optimization of physiological processes, cellular structures and organization, and other in vivo-like functionalities occur.  Therefore, 3D spheroid cultures may be the missing link to overcome the in vitro to in vivo data inconsistencies prevalent in cancer research.

06:37 – Slide 6

A variety of systems are available to culture 3D spheroid models, such as the forced-floating method, hanging drop method, microfluidics platforms, and scaffold and matrix-based approaches.  Each of these systems has their own advantages and limitations, and no single method is inferior to the other.  It all depends on your specific research question.

07:08 – Slide 7

Here at the Centre of Excellence for Pharmaceutical Sciences, we culture our 3D spheroid cell models in clinostat-based rotating bioreactors on a CelVivo BAM system.  Dr. Carlemi Calitz described this system comprehensively in her webinar of the 24th of May, which is still available on demand at LabRoots.  Basically, each CelVivo BAM system consists of a driving unit, wireless communications and an environmental control.

07:48 – Slide 8

The CelVivo rotating bioreactors are ready to use with a cell chamber with two openings for quick sampling and medium replacement, as well as a water chamber with a wick and 0.2 micron membranes for optimum gas exchange and humidity.  We use AggreWells to generate our spheroids before we transfer them to the rotating bioreactors.  These AggreWells allow us to produce approximately 800 to 1,200 spheroids per well depending on the number of microwells.

08:32 – Slide 9

So now I’m going to show you a video of how a rotating bioreactor looks with spheroids in.

09:03 – Slide 10

Furthermore, these spheroids are uniform in size and can be generated within 24 hours, depending on the cell line.  Spheroids cultured in this manner usually reach their metabolic equilibrium after 18 to 21 days and can remain stable for a further 21 days.  Therefore, longer drug exposures can be investigated than traditional 2D experiments.  (09:35)

As I’ve mentioned earlier, we are currently establishing three-dimensional cell culture models for multidrug-resistant cancer research.  Our main goal is to develop a research platform for multidrug-resistant small cell lung cancer.  Seeing as approximately one out of six deaths worldwide are associated with cancer, it remains a devastating and serious health concern globally.  (10:08) It has been reported that in 2015, 8.8 million cancer deaths were documented worldwide, which substantiates the need for breakthroughs in cancer drug research to overcome the continuous fight against cancer.  Small cell lung cancer without treatment is the most aggressive of all the pulmonary tumors, with a survival period of only two to four months.  (10:41) It is highly metastatic and even though small cell lung cancer tumors show sensitivity to chemotherapy and radiation, the occurrence of drug resistance and disease relapse is very common.

10:56 – Slide 11

One of the mechanisms by which cancer cells acquire drug resistance is the active efflux of chemotherapeutic drugs out of the cell to reduce the drug concentration within the cancer cell.  Efflux transporters of the ABC family including P-gp and MRP1 are predominantly overexpressed in various drug-resistant cancers.

11:28 – Slide 12

We are using three human small cell lung cancer cell lines, of which one is chemosensitive, one is multidrug-resistant through overexpression of the MRP1 efflux transporter, and the last one is also multidrug-resistant through overexpression of P-gp.

11:50 – Slide 13

Each of these cell lines were cultured using AggreWells and transferred to rotating bioreactors where the speed was adjusted according to the spheroid size.  It is important to modify your culturing requirements to fit each cell line’s needs.  For example, the MRP1 expressive cell line formed perfectly round, compact spheroids when we seeded 1,000 cells per microwell of an AggreWell 400, followed by an incubation period of 24 hours.  (12:31) The P-gp expressive cell line also formed spheroids, although not so flawless as the first ones, using the same seeding concentration in an AggreWell 400 plate.  However, the incubation period had to be prolonged to 48 hours.  The chemosensitive line is still giving us a bit of a problem as they tend to clump as soon as they are transferred to the bioreactor, but we are busy testing other method modifications at the moment.

13:08 – Slide 14

As to method optimization, each spheroid model is comprehensively characterized to obtain a baseline of the specific model’s growth properties and functionality.  This approach will clarify when the model reaches its dynamic equilibrium phase, indicating when the experimental window can start.  (13:36)

Firstly, we characterize our spheroids based on size and protein content.  By taking daily photomicrographs of the spheroids and measuring the (planar @ 13:48) shadow surface area of the spheroids with (imaging @ 13:52) software, the size is determined.  The Bradford assay is used for protein determination of each spheroid.  This surface area can be directly correlated to the protein content of the spheroids and can be used to calculate the dosage of drugs to be tested in milligrams per kilogram.  This is translatable to in vivo or clinical trials in which chemotherapy is also administered in milligram per kilogram dosages.

14:28 – Slide 15

Secondly, we characterize the spheroids based on their daily cell viability.  By determining the intracellular ATP and extracellular adenylate kinase levels, a broad overview is obtained of the viability of the model over time.

14:49 – Slide 16

Now, specifically for our three small cell lung cancer cell lines, it is necessary to confirm the efflux transporter expression of each.  Therefore, gene expression using specific primers is done to ensure that P-gp and MRP1 are hyperexpressed in the particular line, as indicated by their supplier guidelines.  Other assays and imaging techniques can also be done on the spheroids such as proteomics, histochemistry and transmission electron microscopy.

15:29 – Slide 17

Now that we have established 3D spheroid models, it is time to validate them to ensure that they adhere to our prescriptions, as firstly a tumor-sensitive model, secondly a multidrug-resistant model overexpressing MRP1, and thirdly, a multidrug-resistant model overexpressing P-gp.  In an attempt to validate these three models as a platform for small cell lung cancer research, the accuracy of these 3D spheroids as analogs for in vivo or clinical trials are concerns.  The spheroid models should be validated with well-known standard anticancer drugs for which a vast number of published data are available.  (16:27)

Our three spheroid models are treated according to available clinical or in vivo trial dosages with standard anticancer drugs for 21 days after reaching dynamic equilibrium.  These drugs are specifically chosen for their affinity for our desired efflux transporters.  Drug 1 is not a substrate of particularly P-gp or MRP1.  Drug 2 is a substrate for the MRP1 efflux transporter and Drug 3 is a substrate for the P-gp transporter.  (17:08)

By investigating the cell viability, protein content, gene expression and proteomic data, the efficacy of these drugs against the three small cell lung cancer spheroid models are evaluated.  Therefore, to confirm the susceptibility of the chemosensitive model towards the drug, the same dosage should be compared between the chemosensitive and multidrug-resistant models.  (17:40)

From our 2D investigations, as seen in the table, the resistance index of the multidrug-resistant model was very high relative to the chemosensitive model.  Moreover, to confirm the multidrug-resistance mechanism of the model, a low and a high dosage should be compared within each cell line.  Overall, the MRP1 hyperexpressive model showed a high tumorigenicity towards Drug 2, given that it is resistant to Drug 2, whereas the P-gp hyperexpressive model was highly tumorigenic when treated with Drug 3, being as Drug 3 is a P-gp substrate.  These obtained results should, however, still be investigated in our 3D spheroids.

18:38 – Slide 18

We are investigating several other applications for this validated small cell lung cancer platform.  The rich plant biodiversity of Africa has been the source of medicinal plants for centuries, with many success stories of patients that were cured and new treatments sourced from indigenous plants.  Traditional herbal medicine relies on knowledge handed down from generation to generation and can refer, among others, to the use of remedies based on plants to diagnose, treat or cure conditions.  (19:23) Herbal medicines form a key component of African traditional medicinal practices and in some regions, especially rural areas, traditional medicine may be the main or even the only source of healthcare available.  But it’s also highly popular because of accessibility, affordability and its cultural acceptability.  (19:52)

Some active constituents in herbal medicine can modulate efflux transporter expression and activity, potentially decreasing the multi-drug resistance via efflux.  For example, curcumin, derived from the dried rhizomes of Curcuma longa or turmeric, has been found to inhibit P-gp function and expression in cancer cells, reversing multidrug-resistance effects.  The modification of efflux transporter expression and activity by medicinal plants can potentially be used for the management of multi-drug resistance in cancer cells by reducing efflux of anticancer drugs.  (20:41) Cancer patients often use herbal preparations and traditional medicines concomitantly with their prescribed anticancer drugs.  But the myth exists that traditional medicine of natural origin only holds advantages for users without any adverse or toxic effects.

21:05 – Slide 19

However, herbal medicine may have pharmacokinetic interactions with conventional drugs, altering their bioavailability and effectiveness, therefore the identification of potential herb-drug interactions is necessary for the wellbeing of patients suffering from cancer.  Here is a list of publications in which we have studied herb-drug interactions.  Screening for the anticancer efficacy of newly developed drugs and their combination with traditionally used medicinal plants using 3D cancer cell spheroids may assist in identifying potential new therapies while reducing unnecessary animal testing.

22:00 – Slide 20

In conclusion, 3D spheroid models are becoming the gold standard in preclinical cancer drug screening.  However, it is important to keep in mind that 3D spheroids are not supposed to replace in vivo or clinical trials.  On the contrary, it should rather refine the choice of preferred drugs for a reduced number of further in vivo studies.  But with 3D, the possibilities are endless.

22:37 – Slide 21

I would just like to thank the following entities for funding: the National Research Foundation of South Africa and the South African Medical Research Council, then also CelVivo for the opportunity to use their excellent system, which contributes surely to stress-free (reviews @ 23:00).

23:02 – Slide 22

For more information on the CelVivo BAM system and AggreWells, please see the attached list.

Thank you.  Now you can join us for live questions and answers.  (23:20)

Question:  Thank you, Dr. Willers, for your informative presentation.  We will now start the live Q&A portion of the webinar.  If you have a question you'd like to ask, please do so now.  Just click on the Answer a Question box located on the far left of your screen.  We'll answer as many questions as we have time for.  So let's get started.  Our first question is: how does the MDR1 and P-gp results—excuse me—results in spheroids compare to those in 2D cultures?  (23:56)

Clarissa Willers:  Well, that question, I can actually not answer completely as our results are still not published.  So yeah, we are still in the process of taking weekly samples for gene expression.  So yeah, but we would suggest that the gene expression would be much more stable in the spheroids than in 2D cultures.  (24:29)

Question:  And our next question: how were the EC50s measured?  Can these vary based on endpoints—example, cell death, spheroid size and/or overt cytotoxicity versus inhibition of growth?  (24:46)

Clarissa Willers:  Okay, the EC50s, we used IC50s for the 2D data that I’ve shown in the table.  We measured this with ATP, adenosine triphosphate, assays as well as adenylate kinase level, and then it’s an endpoint after 96 hours.  Let me just understand—and yeah, I don’t know that I answered the question completely.  Yeah, it’s basically cell death and the reduction of the cell viability.  (25:33)

Question:  And Dr. Willers, here is going to be our next question.  In a simple rotation method in order to form spheroids, you used 24 well plates or 6 wells?  And in each one, you have to get one spheroid, so is it the same?  (25:51)

Clarissa Willers:  Okay, let me just understand the question.  So you want to know if we use a 24-well plate?  We use one—one well can make up to 1,000 spheroids.  That means that one microwell in each well gives you—there’s 1,000 cells in each microwell.  That gives you one spheroid.  So yeah, it depends.  The AggreWells we buy are a 24-well plate but you can get around about 1,000 spheroids out of one well, yeah.  (26:42)

Question:  Dr. Willers, we’re getting so many good questions, so here’s our next one.  How can 3D spheroid cells process for gene expression?  (26:55)

Clarissa Willers:  I don’t understand the question.  (27:00)

Question:  It’s question number— (27:01)

Clarissa Willers:  Process for gene expression, yeah?  (27:02)

Question:  Yes.  It’s question number, it’s question number 13.  (27:08)

Clarissa Willers:  So the process, so, okay.  You would sample the spheroid out of the bioreactor, then because our sampling is done before we can do the gene expression, we would store them in RNAlater and then after that, when you want to use them, you just wash the RNAlater out according to the manufacturer guidelines, and then you continue with your RNA extraction.  (27:38) And yeah, your normal real-time PCR.  Yeah, reverse transcription processes.  (27:52)

Question:  After such a long culturing period, how big is your spheroid and how deep would the nutrients or cancer drugs have penetrated through the spheroid?  (28:03)

Clarissa Willers:  Well, our spheroids cultured in the clinostat-based rotating bioreactor can reach up to a size of 1 mm in diameter, although this can vary depending on the type of cell line you use.  Although we have not tested our cancer drug distribution within our spheroids yet, I believe that if you use labile drugs, you will be able to investigate the drug penetration within the spheroids.  (28:37) Given the fact that this culturing system is an irrigated system, there is continuous flow of the media and nutrients around the spheroid, and this results in a smaller diffusion/depletion zone around your spheroids in comparison to other static or buffer systems.  But there are previous studies that have shown that spheroids cultured in rotating bioreactors have sufficient oxygen diffusion throughout the spheroids, even to the core.  (29:13)

Question:  And it looks like our next question is going to be: shouldn’t protein content scale with the volume and not the surface area of the spheroid?  I wouldn’t expect a linear relationship in this case.  (29:26)

Clarissa Willers:  Well, our collaborators in Denmark, they did a lot of studies and they found, they actually found a linear correlation between the spheroids’ surface area, the shadow area that you measure, as well as the protein content.  Yeah, but if you want to do the—if you want to use the volume, it would be a destructive method.  (29:57) You would have to break up your spheroids, so yeah.  Yeah, we don’t do that.  So you can just make a lookup table for each cell type during your characterization.  (30:14)

Question:  Now Dr. Willers, this is a two-part question.  What are the main challenges of 3D culture?  Are there any particular safety concerns?  (30:28)

Clarissa Willers:  Okay.  It’s not, it’s an easy method, but if you don’t have any cell experience, I would rather say that you first get proper training on 2D and then you can move to your 3D processes.  The main challenge for us in South Africa, it is expensive.  The whole BAM system as well as the bioreactors are very expensive and we have to import them into the country.  (31:04) That is a big challenge for us.  Yeah, then the AggreWells are also expensive.  And when the spheroids are very small, they require a daily checkup, yeah, just to adjust their speed and stuff.  (31:25)

And safety concerns, well, it’s cells so we wear our PPE, our personal protective equipment, and our cell lines that we use are Biosafety Level 1.  So yeah, that’s the, yeah, safety concerns regarding 3D.  (31:52)

Question:  Our next question is also a two-part question.  Do you think this technique is cost-effective or is it more expensive than a mice model?  (32:05)

Clarissa Willers:  Okay.  Well, I would say it is much cheaper than a mouse model.  We get a lot of data out of our spheroids during the 42-day period.  You can sample more frequently versus where mice, the sampling periods are limited due to the ethical constraints.  (32:36) And I would say the mice models, if you use xenografts, they take a long period to form proper cancer or a tumor which you can measure the volume of.  It takes at least, let’s say, eight months for a proper xenograft to form.  Yeah, so yeah, so my money is on the 3D.  (33:02)

Question:  We’re getting so many good questions from our audience so let’s continue with these.  What kind of matrix or hydrogel do you use to grow spheroids?  (33:15)

Clarissa Willers:  Well, for our three lines that we, that I discussed on the presentation, there’s no matrix or hydrogel to support the cells.  The moment you put them in the AggreWells, they tend to cluster and form tight links between each other.  So yeah, they don’t have any supporting matrix or scaffold or something.  (33:48) But with other, our—we have another line that my colleague Dr. Carlemi Calitz is working on.  She uses Matrigel; that’s sodium alginate.  Okay, yeah, so I hope that answered the question.  (34:07)

Question:  So, my next one: how will you measure the stability of your drug resistance in your spheroid models for the duration of your experiments?  (34:18)

Clarissa Willers:  As I’ve already mentioned, during characterization, there is a—we do continuous sampling for the gene expression to determine if there's any possible changes in our gene expression profile. Now during the experiments, we will also determine the gene expression weekly, and then you can evaluate the changes induced by your specific drug treatment.  (34:48)

Question:  And it looks like our next question is going to be: is the medium you use for 2D culture the same as you use for 3D culturing?  (35:02)

Clarissa Willers:  Yeah, definitely, but we have found that adding vitamin C, ascorbic acid, to the media in a specific concentration also helps the cells to form a tight spheroid.  Yeah, but the medium is exactly the same.  (35:23)

Question: So it looks like we have about five more minutes to answer any questions so let’s go to our next one. Can we detect metabolic reprogramming of tumor cells in spheroids?  (35:38)

Clarissa Willers:  Yes, you can.  You can do metabolic reprogramming by using proteomics.  If you take out your spheroid and you—yeah, it’s like basically, it’s proteomics.  So yeah, you sample your spheroid.  It’s a disruptive technique but it is possible, yeah.  You can do metabolic profiling.  You can actually look at some of our collaborators’ articles.  It’s Wrzesinski and Fey, 2018.  It is on my list of references.  (36:22)

Question:  So our next question: would it be possible to culture primary cells directly derived from a cancer patient as a spheroid for further personalized medicine application?  (36:38)

Clarissa Willers:  Yes, it is possible.  In fact, primary cultures grown in 2D have a very limited experimental window as they tend to, they tend to dedifferentiate and lose several key characteristics within, let’s say, 72 hours. So therefore, by culturing them in a 3D rotating bioreactor, they can retain their morphology, their viability and organ-specific function for at least four weeks.  (37:12) And therefore, they more closely resemble the in vivo tissues. Now, a patient’s primary tumor cells can be used to generate a number of 3D spheroids, and these spheroids can then be studied concurrently or ahead of the actual patient treatment program.  This approach can help guide the therapeutic management of your clinical trial and introduce key features necessary for the development of personalized medicine.  (37:48)

Question:  It looks like we have another two-part question here.  Do you consider using serum in this model and which serum do you consider in the media?  (38:00)

Clarissa Willers:  Yes, we use—we use FBS in our media, and it’s exactly the same percentage as what you would use in 2D.  I don’t want to say our brand name but yeah, we use normal fetal bovine serum that is for cell work.  It’s sterile-filtered, gamma-irradiated.  Yeah.  (38:30)

Question:  All right, and it looks like we have time for one more question.  If you want to, can you take your spheroid out of the well for metabolic profiling studies?  (38:43)

Clarissa Willers:  Out of the well.  The spheroids are in a bioreactor, so they are not in a well.  They are prepared in the well but then after an incubation period in the wells, you transfer them into your bioreactors.  So from the bioreactors, you do your daily sampling, yeah.  I don’t know why would you want to sample from the well.  (39:17)

Alexis Corrales:  Well, we would like to thank you again, Dr. Willers.  Do you have any final comments for our audience?  (39:27)

Clarissa Willers:  Well, nothing from my side but thank you so much for the opportunity, and if you have any further questions, please follow us on LinkedIn and ResearchGate and Instagram, please look at our list of references.  Yeah, thank you so much.  (39:48)

Alexis Corrales:  Before we go, I’d like to thank the audience for joining us today and for their interesting questions.  Questions we did not have time for today and those submitted during the on-demand period will be addressed by the speaker via the contact information you provided at the time of the registration.  (40:06)

We would like to thank Dr. Willers for her time today and her important research.  We would also like to thank LabRoots and our sponsor, Thermo Fisher Scientific, for underwriting today’s educational webcast.  (40:18)

This webcast can be viewed on demand through February of 2019.  LabRoots will alert you via email when it's available for replay.  We encourage you to share that email with your colleagues who may have missed today's live event.  Until next time, goodbye.

End Presentation:  40:39

Get to know Clarissa

Why did you choose cancer research?
Well, my grandmother on my mother’s side died of osteosarcoma eight years ago, whereas my grandfather on my father’s side died of melanoma three years ago. This is just the closest relatives that lost the fight against cancer; several great-grandparents and uncles also suffered this terrible fate. Seeing the heartbreaking impact cancer had on both sides of the family, motivated me to do cancer research. 

What motivates you to succeed in your field?
I love working with different cancer cell types, to see how their morphology differs and having the satisfaction of successfully culturing a cell line both in 2D and 3D. Furthermore, the prospect of always having the possibility of finding a cure for a devastating disease like cancer is motivating enough.

What are your top 3 favorite things to do outside of the lab?

  1. Working in my vegetable garden
  2. Reading a nice book while staying in my pajamas all day
  3. Shooting a few rounds with my husband at the range

Describe yourself with 3 words
Organized, loyal and hard-working

On your days off, what do you do? 
Normally, it would consist of cleaning the house, laundry, etc. My husband and I like to play with our four-legged children and take them for a walk, as well.

If you could choose any other career what would it be? Why?
I would have liked to be a medical doctor, specializing in surgical oncology. I think it is fulfilling to remove a tumour from a patient with severe symptoms and have the potential to make such a patient cancer-free. Secondly, medical doctors receive a higher salary than academic researchers, don’t they?

Which scientist current or past would you most like to meet and why? 
Prof. Irving Weissman, Director of the Institute of Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine. I would really like to hear what he thinks about the Cancer stem cell theory, seeing as several scientists are skeptic about this idea. I, on the other hand, think cancer stem cells do exist and play an essential role in cancer multidrug resistance and sudden recurrence after remission.

Is outreach/STEM important to you? Why?
Science, Technology, Engineering and Mathematics (STEM) are undeniably an important part of my research. These four aspects form the basic pillars of our daily lives in South Africa. To improve our future education, research and the overall economic development of the country, STEM should be funded without hesitation.

If you didn’t have to sleep, what would you do with the extra time? 
Read, read, read. Be it either to read a book or to read an article. And play with our dogs.

Who inspires you to be better? 
Besides my husband, I would also say my parents. They made so many sacrifices to ensure that we, as children, had a proper head start in life. By achieving success as a scientist, their sacrifices were not in vain.

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