Although immune checkpoint blockade therapies have demonstrated clinical efficacy in cancer treatment, harnessing this strategy is largely encumbered by resistance in multiple cancer settings. Here, we show that tumor-infiltrating T cells are severely exhausted in the microsatellite stable (MSS) colorectal cancer (CRC), a representative example of PD-1 blockade–resistant tumors. In MSS CRC, we found wound healing signature to be up-regulated and that T cell exhaustion is driven by vascular endothelial growth factor-A (VEGF-A). We report that VEGF-A induces the expression of transcription factor TOX in T cells to drive exhaustion-specific transcription program in T cells. Using a combination of in vitro, ex vivo, and in vivo mouse studies, we demonstrate that combined blockade of PD-1 and VEGF-A restores the antitumor functions of T cells, resulting in better control of MSS CRC tumors.
WNT signaling activation in colorectal cancers (CRCs) occurs through APC inactivation or β-catenin mutations. Both processes promote β-catenin nuclear accumulation, which up-regulates epithelial-to-mesenchymal transition (EMT). We investigated β-catenin localization, transcriptome, and phenotypic differences of HCT116 cells containing a wild-type (HCT116-WT) or mutant β-catenin allele (HCT116-MT), or parental cells with both WT and mutant alleles (HCT116-P). We then analyzed β-catenin expression and associated phenotypes in CRC tissues. Wild-type β-catenin showed membranous localization, whereas mutant showed nuclear localization; both nuclear and non-nuclear localization were observed in HCT116-P. Microarray analysis revealed down-regulation of Claudin-7 and E-cadherin in HCT116-MT vs. HCT116-WT. Claudin-7 was also down-regulated in HCT116-P vs. HCT116-WT without E-cadherin dysregulation. We found that ZEB1 is a critical EMT factor for mutant β-catenin-mediated loss of E-cadherin and Claudin-7 in HCT116-P and HCT116-MT cells. We also demonstrated that E-cadherin binds to both WT and mutant β-catenin, and loss of E-cadherin releases β-catenin from the cell membrane and leads to its degradation. Alteration of Claudin-7, as well as both Claudin-7 and E-cadherin respectively caused tight junction (TJ) impairment in HCT116-P, and dual loss of TJs and adherens junctions (AJs) in HCT116-MT. TJ loss increased cell motility, and subsequent AJ loss further up-regulated that. Immunohistochemistry analysis of 101 CRCs revealed high (14.9%), low (52.5%), and undetectable (32.6%) β-catenin nuclear expression, and high β-catenin nuclear expression was significantly correlated with overall survival of CRC patients (P = 0.009). Our findings suggest that β-catenin activation induces EMT progression by modifying cell-cell junctions, and thereby contributes to CRC aggressiveness.
The diagnosis of solid pseudopapillary neoplasms (SPNs) is challenging because some SPNs share many similar morphological and immunohistochemical features with other pancreatic neoplasms. In this study, we investigated potential diagnostic markers of SPN.Based on the SPN-specific upregulated genes from a previous DNA microarray and proteome study, we selected six immunohistochemical markers [beta-catenin, androgen receptor (AR), lymphoid enhancer-binding factor 1 (LEF1), transcription factor for immunoglobulin heavy-chain enhancer 3 (TFE3), fused in sarcoma (FUS), and WNT inhibitory factor 1 (WIF-1)]. We also evaluated the Ki-67 proliferative index to investigate its associations with prognosis. To validate these markers, we studied 91 SPNs as well as 51 pancreatic ductal carcinomas (PDC) and 48 neuroendocrine tumors (NET) as controls.We found frequent and diffuse nuclear expressions of β-catenin (98.9%), AR (81.3%), LEF1 (93.4%), TFE3 (74.7%), FUS (84.6%), and cytoplasmic expression of WIF-1 (96.7%) in SPNs. In contrast, PDCs and NETs showed no expression. (P < 0.001). When beta-catenin, LEF1, and TFE3 staining were combined, the sensitivity and specificity were 100% and 91.9%, respectively. Four (4.4%) SPNs showed distant metastasis and these tumors were associated with a relatively high Ki-67 proliferative index (≥ 5%; P = 0.013).We identified LEF1, TFE3, and AR as putative diagnostic markers of SPN, auxiliary to β-catenin. Incorporated into an immunohistochemical panel, these markers could be beneficial to distinguish SPN from PDC and NET. In addition, we suggest that the Ki-67 proliferative index can be a predictive marker of metastasis in SPNs.
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