T-cell exhaustion is a phenomenon that represents the dysfunctional state of T cells in chronic infections and cancer and is closely associated with poor prognosis in many cancers. The endogenous T-cell immunity and genetically edited cell therapies (CAR-T) failed to prevent tumor immune evasion. The effector T-cell activity is perturbed by an imbalance between inhibitory and stimulatory signals causing a reprogramming in metabolism and the high levels of multiple inhibitory receptors like programmed cell death protein-1 (PD-1), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), and Lymphocyte-activation gene 3 (Lag-3). Despite the efforts to neutralize inhibitory receptors by a single agent or combinatorial immune checkpoint inhibitors to boost effector function, PDAC remains unresponsive to these therapies, suggesting that multiple molecular mechanisms play a role in stimulating the exhaustion state of tumor-infiltrating T cells. Recent studies utilizing transcriptomics, mass cytometry, and epigenomics revealed a critical role of Thymocyte selection-associated high mobility group box protein (TOX) genes and TOX-associated pathways, driving T-cell exhaustion in chronic infection and cancer. Here, we will review recently defined molecular, genetic, and cellular factors that drive T-cell exhaustion in PDAC. We will also discuss the effects of available immune checkpoint inhibitors and the latest clinical trials targeting various molecular factors mediating T-cell exhaustion in PDAC.

Introduction: Sunitinib is a tyrosine kinase inhibitor that binds to vascular endothelial factor receptor currently used for the treatment of renal cell carcinoma, as well as for several other conditions such as gastrointestinal stromal tumors and pancreatic neuroendocrine tumors. We present a patient with invasive diarrhea who was treated with sunitinib for metastatic renal cell carcinoma. Case report: Drug induced colitis was confirmed with colonoscopy from histopathological specimens. Clinical recovery of diarrhea was achieved with oral budesonide. Remarkably, the pathologic findings were observed in both the macroscopically normal mucosa and the mucosa with aphthous ulcers in the colon. Management & outcome: The patient was treated for sunitinib associated diarrhea, after exclusion of the other reasons. Metronidazole and piperacillin/tazobactam treatment were prescribed. Discussion: Diarrhea is a frequent symptom in patients treated with tyrosine kinase inhibitors, however the described pathologic findings have rarely been reported. Our aim is to emphasize the importance of close follow-up in patients treated with tyrosine kinase inhibitors, and to raise awareness on the management of sunitinib induced colitis.