Funded Research

Identification of Metastatic Modulators through Zebrafish Modeling

Identification of Metastatic Modulators through Zebrafish Modeling

Identification of Metastatic Modulators through Zebrafish Modeling

Shruthy Suresh, PhD

Mentor Richard White, MD, PhD
Award Type Career Development Award
Institution Memorial Sloan Kettering Cancer Center

Description:

Melanomas arise from pigmented cells called melanocytes, typically in the skin. Melanomas can spread to distal parts of the body, through a process called metastasis. Metastasis is the primary cause of mortality in all cancers; melanomas have the highest propensity to metastasize to the brain, contributing to the poor prognosis. Although significant progress has been made in melanocyte biology, the factors influencing metastasis still remain largely unknown. The major cause of melanoma is due to ultra-violet radiation exposure, which causes a large number of mutations in melanocytes. Large-scale sequencing efforts have identified frequently occurring DNA mutations in melanoma, but this approach fails to distinguish between passenger mutations and mutations that actually drive the disease. The role of neighboring cells such as adipocytes or immune cells adds further complexity to understanding factors driving metastasis. For example, the White lab recently uncovered a novel role for adipocytes in driving melanoma. Thus, animal models with an intact immune system that faithfully recapitulate human melanoma are crucial to identify mechanisms regulating metastasis.

Here, we propose to utilize the zebrafish to study melanoma. Zebrafish are easy to breed in large numbers and form melanomas histologically and genetically similar to human melanomas. The optically transparent zebrafish casper, developed in the White lab, allows for easy visualization of melanoma by fluorescence imaging. For example, we can image cancer cells at the single cell level and track its fate within the animal. We collaborated with the Adams lab at the Sanger Center to obtain data from the AVAST-M clinical trial, the largest adjuvant study in high-risk primary melanoma. In this study, 466 patients underwent sequencing of the primary tumor to generate high quality sequencing data. Extensive clinical details were collected such as pathological details on the primary tumors and importantly, whether the patient did or did not ultimately metastasize. We used this powerful dataset to ask whether the expression of certain genes might predict metastasis in general, or more specifically to the brain, which has led us to a list of 60 exciting candidate genes. Additionally, the White lab has developed a method called Transgene Electroporation in Adult Zebrafish (TEAZ) to model melanoma. In TEAZ, mutations are induced in melanocytes, similar to what occurs in human melanomas, using powerful CRISPR-Cas9 based genome editing, which results in aggressive melanoma.

In this study, we propose to use TEAZ and CRISPR-Cas9 to delete candidate genes in zebrafish and monitor metastasis by fluorescence imaging. We will also assess if there are specific factors driving metastasis to the brain, which remains the most aggressive subtype of melanoma. We anticipate that this study will help identify new regulators of metastasis and pave the way for novel therapeutic targets in melanoma.

Elucidating Metabolic Changes that Occur in Melanoma Brain Metastases

Elucidating Metabolic Changes that Occur in Melanoma Brain Metastases

Elucidating Metabolic Changes that Occur in Melanoma Brain Metastases

Zachary Schug, PhD

Mentor Meenhard Herlyn, DVM, DSc
Award Type Career Development Award
Institution The Wistar Institute

Description:

Melanoma is the third most common malignancy to metastasize to the brain. It is estimated that at least 50% of patients with stage IV melanoma will develop brain metastases during the course of disease. There is now abundant evidence that some of the most common treatment options for non-resectable melanoma brain metastases, such as radiotherapy and targeted therapies, fail to confer complete responses in patients and offer little to no benefit for survival. A common reason for the failure of radiotherapy and anticancer drugs in patients with melanoma brain metastases is due to presence of therapy resistant cancer cells within the tumor. One of the driving forces that creates these resistant cell populations in the tumor is the constant state of stress that melanoma cells are exposed to in the tumor microenvironment. Melanoma cells must adapt to cope and survive these harsh and unhospitable conditions in the tumor. The consequence of this is the emergence of melanoma cells that are more aggressive and more resistant to treatment.

In our proposal, we describe a metabolic pathway that supports cancer cell survival during these episodes of stress in the tumor. Indeed, the enzymes we propose to target are involved in supporting melanoma tumor growth and promoting the transition to a more aggressive and resistant state during stress. We propose that targeting these enzymes will help prevent metastasis to the brain and help to treat patients with existing melanoma brain metastases. Since melanoma brain metastases are currently associated with dismal survival rates, our studies have the potential to address a significant unmet clinical need. We expect the proposed studies to advance the translation of our findings to the clinic and help reduce melanoma brain metastasis disparities.

CXCL9 as an Immune Anti-Melanoma Therapy in Combination with BRAF Inhibition

CXCL9 as an Immune Anti-Melanoma Therapy in Combination with BRAF Inhibition

CXCL9 as an Immune Anti-Melanoma Therapy in Combination with BRAF Inhibition

Lawrence Kwong, PhD

Mentor Patrick Hwu, MD
Award Type Career Development Award
Institution The University of Texas MD Anderson Cancer Center

Description:

A major obstacle to even the best melanoma therapies is that in the majority of cases, the tumor never completely goes away. Even if a little bit remains, called the minimal residual disease, the tumor can eventually start growing again and be drug-resistant. Very little is known about how and why these particular cells manage to survive, so we have taken a comprehensive approach using mouse modeling, human patient samples, and sophisticated genetic analyses to identify what goes on in melanoma residual disease after BRAF inhibition (“BRAFi”). We discovered that a functionally critical immune response to BRAFi starts off strong, but then rapidly recedes, leaving behind the residual tumor cells that somehow evaded or suppressed the immune response. We computationally identified a protein, CXCL9, that decreases at the same time as the immune response and that is predicted to regulate it. Given its known function, we speculate that this “chemokine” primarily recruit T cells into the tumor to aid rejection of the cancer, and that loss of its expression in the tumor over time contributes to the tumor evading the subsequently decreased immune response. We therefore hypothesized that when CXCL9 is forced into the tumors, it would sustain the anti-cancer immune response to further attack the residual cells. Indeed, in a pilot study using our mouse models, we found that injecting CXCL9 into a mouse tumor undergoing BRAFi resulted in the majority of tumors being completely eradicated, and they did not regrow when therapy was stopped.

In this proposal, we further explore CXCL9 therapeutically and mechanistically. First, we will develop a new method of CXCL9 delivery to tumors that should increase its stability: by encapsulating the CXCL9 in small “nanoparticles”, these will protect the protein from degradation long-term, while slowly releasing it into the tumor. This also simplifies the treatment, as these nanoparticles could theoretically be delivered once a week instead of needing daily administration. Second, we will ask which immune cells are recruited to the tumor by CXCL9, and then determine which of the immune cells are most important for carrying out the anti-tumor activity by systematically ablating them from the tumor. This knowledge will help future refinements of CXCL9 as an immunotherapy. The long-term goal of this proposal is to establish CXCL9 as a potential clinical therapy in combination with BRAFi, as a way to target minimal residual disease and prevent tumor relapse in patients.

Defining the Mechanisms of Resistance to Anti-CTLA4 Antibodies in the TME

Defining the Mechanisms of Resistance to Anti-CTLA4 Antibodies in the TME

Defining the Mechanisms of Resistance to Anti-CTLA4 Antibodies in the TME

Jeffrey Ravetch, MD, PhD

Award Type Established Investigator Award
Institution The Rockefeller University

Description:

Over the past decade, harnessing the power of a patient’s own immune system for the treatment of cancer has been a major medical breakthrough. By using drugs to block inhibitory signals on immune cells, these medicines help “release the brakes” allowing them to kill cancer cells. One of these drugs is an antibody directed against a protein called CTLA-4. So transformative to the care of patients with melanoma and other cancers, the investigators who initially described such pathways were recently awarded the Nobel Prize. While these therapies have been lifesaving for many, they still fail to benefit the majority of patients receiving them. The reason for this lack of activity in some remains poorly understood. We recently uncovered a mechanism of how this may happen, in that cancers develop another “checkpoint” preventing the activity of anti-CTLA-4 antibodies at the tumor site. This checkpoint, called FcyRIIB, becomes increased in tumors and limits the ability of anti-CTLA-4 antibodies to deplete an important cell type contributing to the suppression of anti-cancer immunity. These studies will investigate this pathway in pre-clinical models and patient specimens, with the goal of using this knowledge to translate improved anti-CTLA-4 antibodies into the clinic.