Mark Eckert (meckert@ucsd.edu)

Graduate Program:  Molecular Pathology
Lab PI: Dr. Jing Yang
Undergraduate Institution: NC State University
Med-into-Grad Clinical training area: Cancer
Main clinical mentor:
Dr. Stephan Howell for Inpatient  showell@ucsd.edu
Dr. Luda Bazhenova for Outpatient  lbazhenova@ucsd.edu

Quote:   “Although I work on the more basic mechanisms of local invasion and metastasis, I’ve become more interested in therapies specifically targeting disseminated tumor cells. This was an idea that I brought into the clinic, and its importance as a clinical need was definitely reinforced by what I observed. Patients with large or numerous metastases were basically untreatable because any therapy that would kill the cancer would probably kill the patient as well. So it definitely made me more enthusiastic about my future career goals and optimistic that it would have clinical relevance. It also made me think a lot what is necessary to translate something into the clinic. Throwing data out into the world by publishing it isn’t sufficient if you don’t follow up on it thoroughly."

Rational for Med-into-Grad training:
     During graduate school, my research has focused on understanding the epithelial-mesenchymal transition (EMT) and how it actively promotes local invasion and metastasis. More specifically, I focused on how the transcription factor Twist1 regulates local invasion by promoting the formation of structures called invadopodia. These basally-localized projections from cancer cells regulate invasion by concentrating protease activity to areas of the cell in contact with the extracellular matrix (ECM). I found that formation of these structures is regulated by PDGFR activity downstream of Twist1 and is essential for Twist1-mediated invasion and metastasis in a variety of in vitro and in vivo models.
     I have always been interested in doing work that has application to the human disease, primarily by identifying new biomarkers or new targets for therapeutic intervention. While preparing my manuscript, we were challenged to demonstrate the human relevance of the pathways that we had identified in mouse models. This led us to use both microarray and tissue arrays to determine if Twist1 and PDGFRs were correlated with metastasis. Upon finding a negative correlation between Twist1 and survival in human samples, I was interested in learning more about how biomarkers are applied clinically. I am also very interested in pursuing research in therapeutics targeting disseminated tumor cells and the metastatic niche, and felt that the MiG program would provide further clinical background that would be useful in those fields.

Medical training and identification of medically-relevant research issues: 
My Med-into-Grad training consisted of a mixture of inpatient and outpatient experiences combined with attendance of cancer case conferences and rounds. Inpatient rounds were useful in learning what information is used to make everyday decisions in cancer therapy and to learn interesting background details about cancer progression from the attending physicians. Outpatient rounds were interesting to see continuity of care from inpatient experiences, as well as how standard chemotherapy regimens and targeted therapies are applied. The education series and boards were very useful in learning about staging, pathology, and diagnosis. (Additional research areas are listed in some of the below sections).

Potential Research collaborations:
    A large number of researchers at UCSD are beginning to look at circulating tumor cells (CTCs) in human patients. A large open question in the field is how to interpret the data, beyond looking at the raw numbers of CTCs. What markers are important? Do physical changes in the cells reflect changes in prognosis? As we work on a transcription factor, Twist1, that promotes local invasion and metastasis, it would therefore be interesting to look at potential interactions between Twist1, EMT, and CTCs.
    With access to CTCs, we could investigate the potential use of markers of EMT, such as gain of N-cadherin and loss of E-cadherin, on prognosis (assuming the data is sufficiently annotated). In addition, EMT causes dramatic changes in cell shape and spreading in 2D culture, including changes in nuclear volume. It would therefore be interesting to look at the purely physical measurements of CTCs (diameter, number of projections, nuclear volume, etc) to see if these characteristics are associated with survival or the epithelial-mesenchymal transition. This is a field we have worked on to some extent with mouse models in lab and will probably move to human data once the mouse data is properly analyzed. Technologies to isolate CTCs are still being optimized, so to some extent any collaborations will depend on access to reliable methods.

Training in diagnostics & therapeutics, and identification of unmet diagnostic & therapeutic needs:
I feel like I received a very solid understanding of current therapies. Diagnostics is relatively straightforward in most cases, based on presentation and histopathology. Staging is more controversial, but there are quantitative rubrics in place in most cases. Therapeutics still primarily consist of some combination of radiation and cytoxics, with targeting therapeutics becoming a promising alternative or supplement in cancers with a known driver mutations. There is definitely a large aspect of personalized medicine in regard to targeted inhibitors. Immune therapy, especially IL-2 therapy, is definitely something the doctors find exciting and see a lot of promise in. I feel like there are a huge number of potential targets and drugs; the challenge is in finding which ones are worthy of follow-up and translation into the clinic. I feel like this is a case where if you are passionate about what you work on, it is your responsibility to translate that passion into further pre-clinical research and to build connections with both medicine and healthcare companies.

Diagnostic & Therapeutic collaborations:
    A major need in the field beyond diagnosis is staging: there is a significant amount of overlap in survival and outcome between stages that, if addressed, could more properly dictate more aggressive treatment. One possibility to improve staging would be to directly measure the ability of tumor biopsy samples to degrade components of the ECM to directly measure the ability of tumor cells to invade locally.
    Within the invadopodia research field, the FITC-gelatin degradation assay is an essential method in assaying the ability of cells to degrade extracellular matrix. Briefly, coverslips are covalently coated with fluorescent gelatin conjugated to FITC. Cells are then plated on top of this substrate and allowed to incubate for some period of time ranging from hours to days (depending on the cell line used). When imaged with a fluorescence microscope, areas where the cell degraded the matrix appear as black areas underneath the cells. The assay is inexpensive, reliable, and may be quantified.
    Directly imaging protease activity in tumors is difficult. Use of protease-specific antibodies (MT1-MMP, MMP2, etc) for immunohistochemistry does not reflect the possibility that the proteases are not in their active form. Although antibodies specifically targeting cleaved ECM components have been generated, they are prohibitively expensive and unreliable. Application of the FITC-gelatin degradation assay to tumor samples would therefore provide an ideal way of measuring the ability of a tumor to degrade ECM components.
     We have recently optimized a protocol in which the basic principles of the FITC-gelatin degradation assay can be applied to paraffin-embedded or frozen tumor sections. Direct application of tumor sections onto a FITC-gelatin substrate is difficult; we therefore instead use a similar substrate, DQ-gelatin. In contrast to FITC-gelatin, DQ-gelatin is non-fluorescent until proteolytically cleaved. Upon cleavage, the substrate becomes highly fluorescent. DQ-gelatin may be mixed with 1% agarose and directly applied to a tumor section. After incubation for only a few hours, clear areas of DQ-gelatin activation can be visualized, particularly at the invasive front of tumors.
    Although, we have only done the preliminary experiments in mice, it has potential applications to tumor tissue samples. The assay also provides another great advantage: it measures the ability of the tumor to degrade a specific substrate while remaining agnostic about the actual identity of the proteases that are degrading the ECM component. As tumors are heterogenous and constantly evolving under various selective pressures, this assay provides a direct answer to the question: can this tumor degrade gelatin (or collagen, or fibronectin; there are multiple substrates available for this assay) without looking at specific proteases.
    There is potential for this assay to be used on human samples in the lab, as we are in the process of beginning a large collaboration with a group in Israel with significant access to human breast cancer tissue specimens. Potentially, ability to degrade specific ECM components could become an aspect of the staging process if robust enough to reflect differences in survival, outcome, or response to therapy.

Long term impact: 
Although I work on the more basic mechanisms of local invasion and metastasis, I’ve become more interested in therapies specifically targeting disseminated tumor cells. This was an idea that I brought into the clinic, and its importance as a clinical need was definitely reinforced by what I observed. Patients with large or numerous metastases were basically untreatable because any therapy that would kill the cancer would probably kill the patient as well. So it definitely made me more enthusiastic about my future career goals and optimistic that it would have clinical relevance. It also made me think a lot what is necessary to translate something into the clinic. Throwing data out into the world by publishing it isn’t sufficient if you don’t follow up on it thoroughly.

Advice for new trainees--Autumn preparatory quarter:
    The Friday lecture series is a helpful introduction, especially to a lot of unfamiliar terminology. You also start to see the names of drugs and treatments you’ll see again and again in the clinic. It’s useful to know the basic mechanisms behind the drugs so you can ask why certain drug combinations are used with certain cancers and the role of radiation. There are a lot of subtleties of treatment you can’t really appreciate unless you know what the drugs are doing and how radiation therapy works.
    Histology is a useful skill to have, but it is honestly not used very often. Although the physicians are very comfortable interpreting PET/CTs and MRIs, they pretty much take the pathologist’s word on anything related to histopathology. In Heme/Onc we did see a lot of blood smears which was something completely unfamiliar with me. Just being able to recognize the basic cell types and understanding what causes some of the red blood cell defects is sufficient to understand what they’re looking for, though.

Advice for new trainees—Winter clinical training quarter:
I think we talked about this a lot during the presentations. Probably the main benefit is starting inpatient rotations earlier (you definitely don’t need to know the doctors before you start; you get to know them quickly just from being in inpatient rounds all day). How to behave is pretty commonsense—dress nice, don’t ask questions in front of the patients, etc. Definitely don’t be reluctant to ask questions or be intimidated by the questions from the physicians. Use your smartphone or get a pocket guide to reference: you’ll hear a lot of terminology you’ve never heard before. Clinic can sometimes be emotional, especially when families are involved, but it moves so fast that you don’t have long to dwell on anything.

Take home perspective on Med-into-Grad at UCSD: 
    Med-into-Grad was definitely an overall positive experience. I would and have recommended it almost everybody with a sincere interest in doing work that has clinical relevance. I think one of the main values is in making the abstract more concrete; seeing what having cancer is really like and how it’s treated affects how you think about what questions are interesting in a subtle way.
    Probably the biggest impact is the fact that a lot of the patients are obviously in a bad situation and desperate for hope. When they find out you’re a cancer researcher, they’re almost universally enthusiastic and hope you’re looking for a “cure”. Even though that’s not realistic, it’s something that makes you think when you’re doing a project: are you doing something that will impact people positively? Science is very skeptical by its very nature, so seeing that kind of naïve enthusiasm really did affect me.