TGFß-Responsive Stromal Activation Occurs Early in Serrated Colorectal Carcinogenesis.

Activated TGFß signaling in the tumor microenvironment, which occurs independently of epithelial cancer cells, has emerged as a key driver of tumor progression in late-stage colorectal cancer (CRC). This study aimed to elucidate the contribution of TGFß-activated stroma to serrated carcinogenesis, representing approximately 25% of CRCs and often characterized by oncogenic BRAF mutations. We used a transcriptional signature developed based on TGFß-responsive, stroma-specific genes to infer TGFß-dependent stromal activation and conducted in silico analyses in 3 single-cell RNA-seq datasets from a total of 39 CRC samples and 12 bulk transcriptomic datasets consisting of 2014 CRC and 416 precursor samples, of which 33 were serrated lesions. Single-cell analyses validated that the signature was expressed specifically by stromal cells, effectively excluding transcriptional signals derived from epithelial cells. We found that the signature was upregulated during malignant transformation and cancer progression, and it was particularly enriched in CRCs with mutant BRAF compared to wild-type counterparts. Furthermore, across four independent precursor datasets, serrated lesions exhibited significantly higher levels of TGFß-responsive stromal activation compared to conventional adenomas. This large-scale analysis suggests that TGFß-dependent stromal activation occurs early in serrated carcinogenesis. Our study provides novel insights into the molecular mechanisms underlying CRC development via the serrated pathway.

The tumor cell-intrinsic cGAS-STING pathway is associated with the high density of CD8+ T cells after chemotherapy in esophageal squamous cell carcinoma.

BACKGROUND: Chemotherapy has the potential to induce CD8+ T-cell infiltration in the tumor microenvironment (TME) and activate the anti-tumor immune response in several cancers including esophageal squamous cell carcinoma (ESCC). The tumor cell-intrinsic cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway has been known as a critical component for regulating immune cell activation in the TME. However, its effect on the infiltration of immune cells induced by chemotherapy in the ESCC TME has not been investigated. METHODS: We examined the effect of the tumor-cell intrinsic cGAS-STING pathway on the infiltration of CD8+ T cells induced by chemotherapy in ESCC using ESCC cell lines and surgically resected ESCC specimens from patients who received neoadjuvant chemotherapy (NAC). RESULTS: We found that chemotherapeutic agents, including 5-fluorouracil (5-FU) and cisplatin (CDDP), activated the cGAS-STING pathway, consequently inducing the expression of type I interferon and T-cell-attracting chemokines in ESCC cells. Moreover, the tumor cell-intrinsic expression of cGAS-STING was significantly and positively associated with the density of CD8+ T cells in ESCC after NAC. However, the tumor cell-intrinsic expression of cGAS-STING did not significantly impact clinical outcomes in patients with ESCC after NAC. CONCLUSION: Our findings suggest that the tumor cell-intrinsic cGAS-STING pathway might contribute to chemotherapy-induced immune cell activation in the ESCC TME.

[A Case of MSI-High Sigmoid Colon Cancer in Which Long-Term Survival Was Achieved by Pembrolizumab for Recurrent Lesions Resistant to Conventional Chemotherapy].

The patient underwent sigmoidectomy with D3 lymph node dissection and partial bladder resection for sigmoid colon cancer(cT4bN1M0, cStage Ⅲa), after preoperative chemotherapy with mFOLFOX plus panitumumab, and FOLFOXIRI plus bevacizumab. Postoperative adjuvant chemotherapy was performed by 8 courses of CAPOX. He relapsed hilar lymph nodes and peritoneal dissemination after 13 months after surgery, he underwent resection of the recurrent lesions. Four months after, he developed recurrence in liver and peritoneum. Although he was treated with FOLFIRI plus ramucirumab or aflibercept, resulted in progression of disease, then he received trifluridine tipiracil hydrochloride plus bevacizumab. At this point, the Japanese health insulance had started to cover pembrolizumab, this therapy was started as the fourth chemotherapy after the diagnosis of high frequency microsatellite instability(MSI), and then tumor markers rapidly declined. He underwent 38 courses of pembrolizumab, the recurrent lesions both liver and peritoneum disappeared. He had stoma closure, peritoneal dissemination disappeared not only intraoperatively but also in histologically from the peritoneal scar. He has received pembrolizumab for 4 years without another recurrence. Here, we report a case of MSI-high sigmoid colon cancer in which long-term survival was achieved by pembrolizumab for recurrent lesions resistant to conventional chemotherapy.

Tumor Infiltrating Effector Regulatory T Cells Express VEGF Receptor 2 in Patients With Colorectal Cancer.

BACKGROUND/AIM: Regulatory T cells (Tregs) suppress various anti-tumor immune responses in the tumor microenvironment (TME) and their control is considered essential to enhancing efficacy of cancer immunotherapy. The purpose of the study was to evaluate the strategy to regulate Tregs through the vascular endothelial growth factor (VEGF) pathway. MATERIALS AND METHODS: We evaluated VEGF receptor (VEGFR) expression in subtypes of Tregs by analysis of public databases and through flow cytometry by investigating surgically resected specimens and peripheral blood mononuclear cells (PBMCs) from 26 patients with advanced colorectal cancer (CRC). RESULTS: Analysis of The Cancer Genome Atlas colorectal adenocarcinoma dataset (n=592) showed that mRNA expression of both FLT1 (VEGFR1) and KDR (VEGFR2) was positively correlated with mRNA expression of FOXP3 as well as Treg signature. Clinical specimens revealed abundant VEGFR2 expression on Tregs, but very marginal VEGFR1 expression. The frequency of effector Tregs, the most immunosuppressive fraction of Tregs, was significantly higher in the tumor than in the PBMC and normal mucosa, and the majority of effector Tregs expressed VEGFR2. Furthermore, by using in vitro generated Tregs, the proportion of Tregs expressing IL-10 or TGF-ß1 was significantly inhibited by a VEGFR2 inhibitor. CONCLUSION: A therapeutic strategy targeting the VEGFR2 axis may have a potential to control effector Tregs in the CRC-TME.

TIM-3 Expression on Dendritic Cells in Colorectal Cancer.

TIM-3 was originally identified as a negative regulator of helper T cells and is expressed on dendritic cells (DCs). Since the inhibition of TIM-3 on DCs has been suggested to enhance T cell-mediated anti-tumor immunity, we examined its expression on DCs within the tumor microenvironment (TME) in colorectal cancer (CRC) using transcriptomic data from a public database (n = 592) and immunohistochemical evaluations from our cohorts of CRC (n = 115). The expression of TIM-3 on DCs in vitro was examined by flow cytometry, while the expression of its related molecules, cGAS and STING, on immature and mature DCs was assessed by Western blotting. The expression of HAVCR2 (TIM-3) was strongly associated with the infiltration of DCs within the TME of CRC. Immunohistochemical staining of clinical tissue samples revealed that tumor-infiltrating DCs expressed TIM-3; however, their number at the tumor-invasive front significantly decreased with stage progression. TIM-3 expression was higher on immature DCs than on mature DCs from several different donors (n = 6). Western blot analyses showed that the expression of STING was higher on mature DCs than on immature DCs, which was opposite to that of TIM-3. We demonstrated that TIM-3 was highly expressed on tumor-infiltrating DCs of CRC and that its expression was higher on immature DCs than on mature DCs.