Stromal Fibroblasts Mediate Anti-PD-1 Resistance via MMP-9 and Dictate TGFβ Inhibitor Sequencing in Melanoma.

I am an Assistant Professor of Medical Oncology who primarily treats patients with colon cancer and gastroesophageal cancers. My laboratory and translational research is focused on tumor immune evasion and immunotherapy, particularly in the setting of metastasis. This work has led to a specific interest in tumor-mediated development of dendritic cell tolerance and suppressive myeloid populations. The ultimate goal of this research is to create biomarker-directed immunotherapies for advanced gastrointestinal cancers.

Our laboratory focuses on transforming growth factor-ß (TGF-ß) superfamily signal transduction pathways, and specifically, the role of these pathways in cancer biology. The TGF-ß superfamily is comprised of a number of polypeptide growth factors, including TGF-βs, bone morphogenetic proteins (BMPs) and activin) that regulate growth, differentiation and morphogenesis in a cell and context specific manner. TGF-ß and the TGF-ß signaling pathway have a dichotomous role in cancer biology, as both tumor-suppressor genes (presumably as regulators of cellular proliferation, differentiation and apoptosis) and as tumor promoters (presumably as regulators of cellular motility, adhesion, angiogenesis and the immune system). This dichotomy of TGF-ß function remains a fundamental problem in the field both in terms of understanding the mechanism of action of the TGF-ß pathway, and directly impacting our ability to target this pathway for the chemoprevention or treatment of human cancers. Resistance to the tumor suppressor effects of TGF-ß is also a common feature of epithelial-derived human cancers (breast, colon, lung, pancreatic, prostate), however, mechanisms for TGF-ß resistance remain undefined in the majority of cases. TGF-ß regulates cellular processes by binding to three high affinity cell surface receptors, the type I, type II, and type III receptors. Recent studies by our laboratory and others have established the type III TGF-ß receptor (TßRIII)  as a critical mediator/regulator of TGF-ß signaling. Specifically we have demonstrated that regulating TßRIII expression levels is sufficient to regulate TGF-ß signaling, and that decreased TßRIII expression is a common phenomenon in human cancers, resulting in cancer progression. TßRIII is also shed from the surface to generate soluble TßRIII, which we have demonstrated has a role in creating an immunotolerant tumor microenvironment. The role of TßRIII and soluble TßRIII in the tumor immune microenvironment is currently being investigated using a multidisciplinary approach.

Activin receptor-like kinase 4 (ALK4) is a type I transforming growth factor-β (TGF-β) superfamily receptor that mediates signaling for several TGF-β superfamily ligands, including activin, Nodal and GDF5. We have demonstrated that mutation or copy number loss of ALK4 occurs in 35% of pancreatic cancer patients, with loss of ALK4 expression associated with a poorer prognosis. ALK4 has also been identified in an unbiased screen as a gene whose disruption enhances Ras mediated pancreatic tumorigenesis in vivo. We have demonstrated that loss of ALK4 expression increases canonical TGF-β signaling to increase cancer invasion and metastasis in vivo. We are currently investigating the mechanism by which loss of ALK4 regulates TGF-β signaling, how it may effect other signaling pathways, and how to use this knowledge to treat pancreatic cancer patients with loss of ALK4 function.

We are interested in understanding the mechanisms that cancers have evolved to suppress the generation of tumor antigen-specific immune responses and how this knowledge can be exploited for the development of novel and more effective cancer immunotherapy strategies. This work involves the utilization of both autochthonous transgenic tumor model systems as well as clinical specimens to develop novel strategies to enhance the efficacy of immunotherapies while also developing predictive biomarkers to better guide the management of cancer patients with these agents. We strive to translate our understanding of the fundamental biochemical and metabolic pathways within the tumor microenvironment that are critical for driving immune evasion and resistance into early phase clinical trial testing.

Our work utilizes a variety of techniques and methodologies that span the breadth of basic biological research. This work integrates studies based on both 1) transgenic mouse tumor models that are monitored using bioluminescence and micro-CT imaging and 2) a variety of clinical specimens.

Our current areas of focus include:

1. Investigating mechanisms of adaptive or acquired immunotherapy resistance in cancer
2. Studying the relationship between EMT pathways and immunotherapy resistance.
3. Elucidating mechanisms of dendritic cell tolerization in the tumor microenvironment and how these processes may contribute to immunotherapy resistance
4. Development of novel pharmacologic and genetic strategies to overcome immunotherapy resistance
5. Investigating mechanisms contributing to select immunotherapy-associated toxicities