TGF-beta signaling and its targeted therapy in gastrointestinal cancers.

The transforming growth factor ß (TGFß) signaling pathway governs physiological homeostasis in the gastrointestinal system and its deregulation can lead to a diverse range of human pathologies including juvenile polyposis syndrome and tumor initiation, progression, and metastasis. In gastrointestinal malignancies, tumor cells evade the known tumor suppressive effects of TGFß signaling through frequent inactivation of the pathway. Paradoxically, tumor cells utilize TGFß-mediated regulation of epithelial-mesenchymal transition and immunomodulation to facilitate the invasive and migratory phenotype of gastrointestinal cancers and avoid immunosurveillance. The dichotomous role of TGFß as both a tumor suppressor and tumor promoter has highly challenged research efforts to specifically target TGFß signaling as a cancer therapy. The current preclinical approach is to inhibit TGFß-mediated generation of a favorable microenvironment for tumor growth, invasion, and metastasis. Here, we overview the alterations of TGFß signaling and its fundamental biological relevance in gastrointestinal tumorigenesis. We further discuss future perspectives for efficacious molecular targeted treatment of contextual TGFß tumor-promoting effects in gastrointestinal cancers.

Tumor-Infiltrating Lymphocyte Function Predicts Response to Neoadjuvant Chemoradiotherapy in Locally Advanced Rectal Cancer.

PURPOSE: The presence of tumor-infiltrating lymphocytes (TILs) in tumors is superior to conventional pathologic staging in predicting patient outcome. However, their presence does not define TIL functionality. Here we developed an assay that tests TIL cytotoxicity in patients with locally advanced rectal cancer before definitive treatment, identifying those who will obtain a pathologic complete response (pCR). We also used the assay to demonstrate the rescue of TIL function after checkpoint inhibition blockade (CIB). PATIENTS AND METHODS: Thirty-four consecutive patients were identified initially, with successful completion of the assay before surgery in those 17 patients who underwent full treatment. An in vitro cytotoxic assay of rectal cancer tumoroids cocultured with patient-matched TILs was established and validated. Newly diagnosed patients were recruited with pretreatment biopsy specimens processed within 1 month. Evaluation of TIL-mediated tumoroid lysis was performed by measuring the mean fluorescence intensity of cell death marker, propidium iodide. CIB (anti-programmed cell death protein 1 [anti-PD-1] antibody) response was also assessed in a subset of patient specimens. RESULTS: Six of the 17 patients achieved an objective pCR on final evaluation of the resected specimen after neoadjuvant chemoradiotherapy. Cytotoxic killing identified the pCR group with a higher mean fluorescence intensity (27,982 [95% CI, 25,340 to 30,625]) compared with the non-pCR cohort (12,428 [95% CI, 9,434 to 15,423]; p < .001). Assessment of the effectiveness of CIB revealed partial restoration of cytotoxicity in TILs with increased PD-1 expression with anti-PD-1 antibody exposure. CONCLUSION: Evaluating TIL function can be undertaken within weeks of the diagnostic biopsy, affording the potential to alter patient management decisions and refine selection for a watch-and-wait protocol. This cytotoxic assay also has the potential to serve as a platform to assist in the additional development of CIB.