SF3B3-regulated mTOR alternative splicing promotes colorectal cancer progression and metastasis.

BACKGROUND: Aberrant alternative splicing (AS) is a pervasive event during colorectal cancer (CRC) development. SF3B3 is a splicing factor component of U2 small nuclear ribonucleoproteins which are crucial for early stages of spliceosome assembly. The role of SF3B3 in CRC remains unknown. METHODS: SF3B3 expression in human CRCs was analyzed using publicly available CRC datasets, immunohistochemistry, qRT-PCR, and western blot. RNA-seq, RNA immunoprecipitation, and lipidomics were performed in SF3B3 knockdown or overexpressing CRC cell lines. CRC cell xenografts, patient-derived xenografts, patient-derived organoids, and orthotopic metastasis mouse models were utilized to determine the in vivo role of SF3B3 in CRC progression and metastasis. RESULTS: SF3B3 was upregulated in CRC samples and associated with poor survival. Inhibition of SF3B3 by RNA silencing suppressed the proliferation and metastasis of CRC cells in vitro and in vivo, characterized by mitochondria injury, increased reactive oxygen species (ROS), and apoptosis. Mechanistically, silencing of SF3B3 increased mTOR exon-skipped splicing, leading to the suppression of lipogenesis via mTOR-SREBF1-FASN signaling. The combination of SF3B3 shRNAs and mTOR inhibitors showed synergistic antitumor activity in patient-derived CRC organoids and xenografts. Importantly, we identified SF3B3 as a critical regulator of mTOR splicing and autophagy in multiple cancers. CONCLUSIONS: Our findings revealed that SF3B3 promoted CRC progression and metastasis by regulating mTOR alternative splicing and SREBF1-FASN-mediated lipogenesis, providing strong evidence to support SF3B3 as a druggable target for CRC therapy.

Influence of High-Risk Pathological Factors and their Interaction on the Survival Benefit of Adjuvant Chemotherapy in Stage II Rectal Cancer: A Retrospective Study.

Objectives: We investigated the impact of high-risk factors in stage II (TNM stage) rectal cancer patients to determine whether they benefit from adjuvant chemotherapy after surgery. Additionally, we explored the interaction between high-risk factors and adjuvant chemotherapy. Our study provides refined guidance for postoperative treatment in patients with stage II rectal cancer. Methods: The retrospective study included 570 stage II rectal adenocarcinoma patients who underwent total mesorectal excision surgery at Tianjin Union Medical Center from August 2012 to July 2019. We employed Cox regression models to assess the collected pathological and clinical factors, identifying the risk factors for overall survival (OS) and disease-free survival (DFS). Additionally, we thoroughly examined the interaction between various high-risk pathological factors and postoperative chemotherapy (ACT), including multiplicative interaction (INTM) and additive interaction (RERI). Results: Among the 570 stage II rectal cancer patients in this study, the average age was 62 years, with 58.9% (N=336) of the population being older than 60. Males accounted for the majority at 64.9% (N=370). Age was found to have an impact on whether patients received adjuvant chemotherapy after surgery (P<=0.001).Furthermore, age (HR: 1.916, 95% CI: 1.158-3.173, P=0.011; HR: 1.881, 95% CI: 1.111-3.186, P=0.019), TNM stage (HR: 2.216, 95% CI: 1.003-4.897, P=0.029; HR: 2.276, 95% CI: 1.026-5.048, P=0.043), the number of lymph nodes cleared during surgery (HR: 1.968, 95% CI: 1.112-3.483, P=0.017; HR: 1.864, 95% CI: 0.995-3.493, P=0.045), and lymphovascular invasion (HR: 2.864, 95% CI: 1.567-5.232, P=0.001; HR: 3.161, 95% CI: 1.723-5.799, P<0.001) were identified as independent risk factors for patients' overall survival (OS) and disease-free survival (DFS). Moreover, the interaction analysis, both multiplicative and additive, revealed significant interactions between the number of lymph nodes cleared during surgery and the administration of adjuvant chemotherapy. For OS (HR for multiplicative interaction: 0.477, p=0.045; RERI: -0.531, 95% CI: -1.061, -0.002) and for DFS (HR for multiplicative interaction: 0.338, p=0.039; RERI: -1.097, 95% CI: -2.190, -0.005). Conclusions: This study provides insights into the complex relationship between adjuvant chemotherapy (ACT) and survival outcomes in stage II rectal cancer patients with high-risk pathological factors. The findings suggest that the number of cleared lymph nodes plays a significant role in the efficacy of ACT and underscores the need for individualized treatment decisions in this patient population.