Macrophages constitute a major component of tumor-infiltrating immune cells. M2 macrophages have been reported to promote tumor progression through promoting tumor angiogenesis and metastasis and regulating T-cell function. Here, we identified a protumorigenic subset of macrophages that constitutively expressed programmed cell death 1 (PD1) and accumulated in advanced-stage gastric cancer (GC). These PD1+ tumor-associated macrophages (TAMs) exhibited an M2-like surface profile, with a significant increase in the expression of CD206, IL-10, and CCL1, and a clear decrease in the expression of MHC class II, CD64, and IL-12 and the ability to phagocytose ovalbumin. Moreover, PD1+ TAMs can suppress CD8+ T-cell function and this immunosuppressive activity can effectively be enhanced upon triggering PD1 signal. GC-derived exosomes effectively educated monocytes to differentiate into PD1+ TAMs with M2 phenotypic and functional characteristics. Together, our results are the first to show that GC-derived exosomes can effectively induce PD1+ TAM generation, and these cells can produce a large number of IL-10, impair CD8+ T-cell function, and thereby create conditions that promote GC progression. Thus, methods in which immunotherapy is combined with targeting PD1+ TAMs and tumor-derived exosomes should be used to restore immune function in GC patients.

Dysregulation of the Wnt/β-catenin signaling pathway is critically involved in gastric cancer (GC) progression. However, current Wnt pathway inhibitors being studied in preclinical or clinical settings for other cancers such as colorectal and pancreatic cancers are either too cytotoxic or insufficiently efficacious for GC. Thus, we screened new potent targets from β-catenin destruction complex associated with GC progression from clinical samples, and found that scaffolding protein RACK1 deficiency plays a significant role in GC progression, but not APC, AXIN, and GSK3β. Then, we identified its upstream regulator UBE2T which promotes GC progression via hyperactivating the Wnt/β-catenin signaling pathway through the ubiquitination and degradation of RACK1 at the lysine K172, K225, and K257 residues independent of an E3 ligase. Indeed, UBE2T protein level is negatively associated with prognosis in GC patients, suggesting that UBE2T is a promising target for GC therapy. Furthermore, we identified a novel UBE2T inhibitor, M435-1279, and suggested that M435-1279 acts inhibit the Wnt/β-catenin signaling pathway hyperactivation through blocking UBE2T-mediated degradation of RACK1, resulting in suppression of GC progression with lower cytotoxicity in the meantime. Overall, we found that increased UBE2T levels promote GC progression via the ubiquitination of RACK1 and identified a novel potent inhibitor providing a balance between growth inhibition and cytotoxicity as well, which offer a new opportunity for the specific GC patients with aberrant Wnt/β-catenin signaling.

Trastuzumab is the backbone of HER2-directed gastric cancer therapy, but poor patient response due to insufficient cell sensitivity and drug resistance remains a clinical challenge. Here, we report that HER2 is involved in cell mitotic promotion for tumorigenesis by hyperactivating a crucial HER2-SHCBP1-PLK1 axis that drives trastuzumab sensitivity and is targeted therapeutically. SHCBP1 is an Shc1-binding protein but is detached from scaffold protein Shc1 following HER2 activation. Released SHCBP1 responds to HER2 cascade by translocating into the nucleus following Ser273 phosphorylation, and then contributing to cell mitosis regulation through binding with PLK1 to promote the phosphorylation of the mitotic interactor MISP. Meanwhile, Shc1 is recruited to HER2 for MAPK or PI3K pathways activation. Also, clinical evidence shows that increased SHCBP1 prognosticates a poor response of patients to trastuzumab therapy. Theaflavine-3, 3’-digallate (TFBG) is identified as an inhibitor of the SHCBP1-PLK1 interaction, which is a potential trastuzumab sensitizing agent and, in combination with trastuzumab, is highly efficacious in suppressing HER2-positive gastric cancer growth. These findings suggest an aberrant mitotic HER2-SHCBP1-PLK1 axis underlies trastuzumab sensitivity and offer a new strategy to combat gastric cancer.

Introduction: Docetaxel, oxaliplatin, leucovorin, and 5-fluorouracil (FLOT) may improve overall survival (OS) in patients with locally advanced gastric cancer (LAGC); however, evidence for its use as a standard treatment has not been established in China. The aim of this study was to investigate the effectiveness, safety, and feasibility of the FLOT regimen as neoadjuvant chemotherapy in Chinese patients with resectable LAGC. Methods: We conducted an observational study to compare the effectiveness of FLOT regimen consisting of docetaxel (60 mg/m 2 ), oxaliplatin (85 mg/m 2 ), leucovorin (200 mg/m 2 ), and 5-fluorouracil (2,600 mg/m 2 as a 24 hr infusion), all given on day 1 and administered every 2 weeks versus initial surgery followed by chemotherapy in patients with clinical T3–4 LAGC. OS was compared by using the Cox proportional hazards regression model and the Kaplan–Meier curve adjusted by inverse probability of treatment weighting (IPTW) and propensity score-matched (PSM) analysis. In addition, we performed subgroup analyses to determine the effectiveness of the FLOT regimen in clinically relevant patient subsets. Results: Overall, 47 patients who received initial FLOT chemotherapy and 269 patients who received initial surgery were enrolled in this study. In the PSM analysis, the FLOT-first group showed favorable OS compared with the surgery-first group (41 vs 41 [HR, 0.416; 95% CI, 0.218–0.794; P =0.008]), and 3-year survival rates were 58.7% and 30.9% in the FLOT-first group and surgery-first group, respectively. IPTW analysis showed similar results. However, the effect of FLOT was low (HR, 0.868; 95 CI%, 0.215–3.504) in patients without lymph node metastasis. Conclusion: Our study suggests that preoperative FLOT chemotherapy is safe and feasible. In terms of OS, FLOT may be superior to initial surgery followed by chemotherapy in reducing morbidity with resectable LAGC.

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