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Siglec‐15, a novel immune suppressor, is upregulated in many human cancers. The aim of this study was to explore the expression of Siglec‐15 in colorectal cancer (CRC), and investigate whether Siglec‐15 could be a potential target for cancer immunotherapy in patients with CRC. We performed immunohistochemical analyses of Siglec‐15 on a cohort of 805 patients with CRC and made comparisons between clinicopathological characteristics, PD‐L1 expression, CD3, CD8, CD45RO tumor‐infiltrating lymphocytes (TILs), and prognosis. We found that Siglec‐15 expression was commonly detected in tumor cells (48.3%) and tumor‐associated stromal cells (33.4%), and was more frequently observed than PD‐L1 expression in tumor cells. In contrast, Siglec‐15 expression was weakly and scarcely found in normal mucosa (13%). Siglec‐15 overexpression in tumor cells was associated with advanced TNM stage (p = 0.020). Co‐expression of Siglec‐15 and PD‐L1 in tumor cells was found in 14.4% of patients, and Siglec‐15 expression was detected in almost half of PD‐L1 negative cases. Elevated Siglec‐15 expression in tumor and stromal cells was associated with sparser CD45RO and CD8 TILs (p = 0.035 and p = 0.004, respectively). The expression of Siglec‐15 did not have prognostic significance. In summary, compared to PD‐L1, Siglec‐15 protein expression is more prevalent in CRC and is associated with advanced disease stage and fewer TILs. These findings support Siglec‐15 as a potential cancer immunotherapy target, in addition to PD‐1/PD‐L1 inhibitors, in patients with CRC. [ABSTRACT FROM AUTHOR]

The present study aims to investigate the roles of nuclear‐enriched abundant transcript 1 (NEAT1) in the regulation of oxaliplatin resistance to gastric cancer (GC). Oxaliplatin‐resistant cell lines were constructed using stepwise selection. NEAT1 knockdown and overexpression of NEAT1 were performed. The 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide (MTT) and colony formation assays were used to evaluate cell proliferation. Propidium iodide (PI) and annexin V staining were used to evaluate cell apoptosis. A dual‐luciferase reporter assay was used to evaluate the molecular interactions. Quantitative polymerase chain reaction (qPCR) was used to determine messenger RNA (mRNA) expression. Western blotting was used to determine the protein expression. Kaplan–Meier's analysis was performed to evaluate the relationship between NEAT1 and poor prognosis in GC. NEAT1 was upregulated in oxaliplatin‐resistant GC cells and associated with poor prognosis in GC patients. NEAT1 knockdown suppressed oxaliplatin resistance, whereas overexpression of NEAT1 induced oxaliplatin resistance. In addition, the expressions of NEAT1 were negatively associated with miR‐26 expressions. Overexpression of NEAT1 attenuated the inhibitory effects of miR‐26 on the enhancer of zeste homolog 2 (EZH2). The roles of NEAT1 in the regulation of oxaliplatin resistance to GC are in part by ameliorating the inhibitory effect of miR‐26 on EZH2. [ABSTRACT FROM AUTHOR]

Gastric cancer (GC) is a frequently diagnosed type of cancer in China, and is associated with a high mortality rate. The biological behavior of GC requires investigation in order to provide an evidence base for the development of strategies to prevent and treat GC. For this purpose, the present review outlines the process of tumor microenvironment (TME) evolution, including the dynamic biological behavior of different types of cancer cell and stroma. Cancer-associated fibroblasts (CAFs) serve as prominent stromal cellular components in the GC TME, and exhibit an essential function in GC progression. In the present study, the function of CAFs in cancer cell proliferation, cell migration, invasion, extracellular matrix remodeling, pathological angiogenesis and immune cell infiltration were investigated. The studies discussed in the present review demonstrate that the cross-talk between CAF, cancer cells and tumor stroma promotes GC progression. [ABSTRACT FROM AUTHOR]

Upregulation of human epididymis protein 4 (HE4) is often observed in different types of cancers, including gastric cancer (GC), but the association of elevated HE4 level with radiation resistance in GC remains unclear. The expression of HE4 and hypoxia-inducible factor 1α subunit (HIF1α) was assessed in GC patient samples and cell lines. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays were performed to reveal the regulation between HE4 and HIF1α. Stable HE4 knockdown and HIF1α overexpression were introduced into GC cell lines to study the role of HE4 in the resistance of GC to radiation therapy. Colony formation assay and the xenograft mouse model were used to investigate the effects of radiation on GC cells. HE4 and HIF1α were upregulated in both GC patient tissues and GC cells. Hypoxia and HIF1α upregulated HE4 by directly targeting the hypoxia response element in its promoter region. Stable HE4 knockdown significantly sensitized GC cells and xenograft tumors to radiation. HIF1α overexpression markedly elevated the radiation resistance of GC cells, which was almost completely abolished by HE4 knockdown. Hypoxia-induced upregulation of HE4 is responsible for resistance to radiation therapy of GC, suggesting that HE4 knockdown or inhibition, combined with radiation therapy, holds great potential in the clinical treatment of GC.

Given the various clinical and pathologic responses to neoadjuvant chemotherapy (NACT) in gastric cancer (GC), potential biomarkers that reflecting the efficacy of NACT on GC should be investigated. The aim of this study was to investigate the 15-PGDH expression response to NACT in GC patients and its relationship with prognosis of GC. Immunohistochemical method was used to assess the level of 15-PGDH expression in 56 GC patients who received NACT before surgery and 46 patients who underwent surgical treatment without NACT as well as their corresponding adjacent non-neoplastic tissues. We found that there was no correlation of 15-PGDH expression between non-cancerous gastric tissues and GC tissues (P=0.519), while 15-PGDH expression level in NACT group was higher than that in nNACT group (P=0.015). In patients with NACT, the higher level of 15-PGDH expression was significantly associated with well-moderately differentiated grade (P=0.023), I/II stage (P=0.014) and with no lymph node metastasis (P=0.016). Moreover, statistically significant differences in overall survival (OS) were found among 15-PGDH expression (log-rank test, P<0.001) and TNM stage (log-rank test, P=0.032). Most importantly, expression of 15-PGDH was found to be an independent predictive factor by multivariate analysis (Hazard ratio (HR) 0.315 [0.120-0.827], P=0.019). These findings indicated that NACT could increase 15-PGDH expression in advanced GC patients, and 15-PGDH may serve as a candidate prognostic biomarker of advanced GC response to NACT.