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


Although anti-PD-1 therapy has improved clinical outcomes for select patients with advanced cancer, many patients exhibit either primary or adaptive resistance to checkpoint inhibitor immunotherapy. The role of the tumor stroma in the development of these mechanisms of resistance to checkpoint inhibitors remains unclear. We demonstrated that pharmacologic inhibition of the TGFβ signaling pathway synergistically enhanced the efficacy of anti-CTLA-4 immunotherapy but failed to augment anti-PD-1/PD-L1 responses in an autochthonous model of BRAFV600E melanoma. Additional mechanistic studies revealed that TGFβ pathway inhibition promoted the proliferative expansion of stromal fibroblasts, thereby facilitating MMP-9-dependent cleavage of PD-L1 surface expression, leading to anti-PD-1 resistance in this model. Further work demonstrated that melanomas escaping anti-PD-1 therapy exhibited a mesenchymal phenotype associated with enhanced TGFβ signaling activity. Delayed TGFβ inhibitor therapy, following anti-PD-1 escape, better served to control further disease progression and was superior to a continuous combination of anti-PD-1 and TGFβ inhibition. This work illustrates that formulating immunotherapy combination regimens to enhance the efficacy of checkpoint blockade requires an in-depth understanding of the impact of these agents on the tumor microenvironment. These data indicated that stromal fibroblast MMP-9 may desensitize tumors to anti-PD-1 and suggests that TGFβ inhibition may generate greater immunologic efficacy when administered following the development of acquired anti-PD-1 resistance. Cancer Immunol Res; 1-13. ©2018 AACR.






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Publication Info

Zhao, Fei, Christine Xiao, Kathy Evans, Bala Thievanthiran, Nicholas DeVito, Alisha Holtzhauasen, Peter Siska, Gerard Blobe, et al. (2018). Stromal Fibroblasts Mediate Anti-PD-1 Resistance via MMP-9 and Dictate TGFβ Inhibitor Sequencing in Melanoma. Cancer immunology research. 10.1158/2326-6066.cir-18-0086 Retrieved from

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Nicholas Christian DeVito

Assistant Professor of Medicine

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.


Gerard Conrad Blobe

Professor of Medicine

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.


Brent A. Hanks

Associate Professor of Medicine

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

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