Survival-associated alternative splicing events interact with the immune microenvironment in stomach adenocarcinoma.

BACKGROUND: Alternative splicing (AS) increases the diversity of mRNA during transcription; it might play a role in alteration of the immune microenvironment, which could influence the development of immunotherapeutic strategies against cancer. AIM: To obtain the transcriptomic and clinical features and AS events in stomach adenocarcinoma (STAD) from the database. The overall survival data associated with AS events were used to construct a signature prognostic model for STAD. METHODS: Differentially expressed immune-related genes were identified between subtypes on the basis of the prognostic model. In STAD, 2042 overall-survival-related AS events were significantly enriched in various pathways and influenced several cellular functions. Furthermore, the network of splicing factors and overall-survival-associated AS events indicated potential regulatory mechanisms underlying the AS events in STAD. RESULTS: An eleven-AS-signature prognostic model (CD44|14986|ES, PPHLN1|21214|AT, RASSF4|11351|ES, KIAA1147|82046|AP, PPP2R5D|76200|ES, LOH12CR1|20507|ES, CDKN3|27569|AP, UBA52|48486|AD, CADPS|65499|AT, SRSF7| 53276|RI, and WEE1|14328|AP) was constructed and significantly related to STAD overall survival, immune cells, and cancer-related pathways. The differentially expressed immune-related genes between the high- and low-risk score groups were significantly enriched in cancer-related pathways. CONCLUSION: This study provided an AS-related prognostic model, potential mechanisms for AS, and alterations in the immune microenvironment (immune cells, genes, and pathways) for future research in STAD.

4,4'­Bond secalonic acid D targets SP cells and inhibits metastasis in hepatocellular carcinoma.

The existence of cancer stem cells (CSCs) is considered to be the main reason for chemoresistance, metastasis and the ultimate failure of treatment in hepatocellular carcinoma (HCC). However, there are a few chemical agents that may inhibit CSCs. The present study identified that 4,4'­bond secalonic acid D (4,4'­SAD), a compound isolated from the marine­derived fungus Penicillium oxalicum, inhibited the growth of side population (SP) cells isolated from human liver cancer cell lines PLC/PRF/5 and HuH­7 by attenuating the expression of ATP­binding cassette superfamily G member 2. Furthermore, the results of wound healing, Transwell, western blotting and reverse transcription­quantitative PCR assays demonstrated that 4,4'­SAD suppressed the invasion and migration of SP cells by downregulating matrix metallopeptidase 9 (MMP­9) and upregulating the antagonist tissue inhibitor of metalloproteinases 1 in vitro. Moreover, in vivo study results found that 4,4'­SAD had anti­lung metastasis efficacy via the decrease of MMP­9 expression in the H22 HCC model of Kunming mice. Therefore, the present study identified the potential of 4,4'­SAD as a promising candidate for the treatment of advanced liver cancer.

Isolation of 4,4'-bond secalonic acid D from the marine-derived fungus Penicillium oxalicum with inhibitory property against hepatocellular carcinoma.

4,4'-bond secalonic acid D (4,4'-SAD) is a known compound isolated from the marine-derived fungus Penicillium oxalicum. No study about the antitumor effect of this compound has been reported, except for a few focusing on its bactericidal properties. Herein, we performed an in vitro biology test and found that 4,4'-SAD stimulated the apoptosis of tumor cells in the human hepatocellular carcinoma cell lines PLC/PRF/5 and HuH-7 by activating caspase-3, caspase-8, caspase-9, PARP, p53, and cyclin B1, as well as by regulating the Bax/Bcl-2 ratio. In vivo studies showed that 4,4'-SAD had antitumor efficacy in H22 cell xenograft model. Immunohistochemical analysis revealed that 4,4'-SAD could regulate Bax expression, which is a biomarker of tumor growth. In summary, 4,4'-SAD significantly inhibited tumor growth both in vivo and in vitro.

Antitumor Effects and Related Mechanisms of Penicitrinine A, a Novel Alkaloid with a Unique Spiro Skeleton from the Marine Fungus Penicillium citrinum.

Penicitrinine A, a novel alkaloid with a unique spiro skeleton, was isolated from a marine-derived fungus Penicillium citrinum. In this study, the isolation, structure and biosynthetic pathway elucidation of the new compound were described. This new compound showed anti-proliferative activity on multiple tumor types. Among them, the human malignant melanoma cell A-375 was confirmed to be the most sensitive. Morphologic evaluation, apoptosis rate analysis, Western blot and real-time quantitative PCR (RT-qPCR) results showed penicitrinine A could significantly induce A-375 cell apoptosis by decreasing the expression of Bcl-2 and increasing the expression of Bax. Moreover, we investigated the anti-metastatic effects of penicitrinine A in A-375 cells by wound healing assay, trans-well assay, Western blot and RT-qPCR. The results showed penicitrinine A significantly suppressed metastatic activity of A-375 cells by regulating the expression of MMP-9 and its specific inhibitor TIMP-1. These findings suggested that penicitrinine A might serve as a potential antitumor agent, which could inhibit the proliferation and metastasis of tumor cells.

The marine fungal metabolite, dicitrinone B, induces A375 cell apoptosis through the ROS-related caspase pathway.

Dicitrinone B, a rare carbon-bridged citrinin dimer, was isolated from the marine-derived fungus, Penicillium citrinum. It was reported to have antitumor effects on tumor cells previously; however, the details of the mechanism remain unclear. In this study, we found that dicitrinone B inhibited the proliferation of multiple tumor types. Among them, the human malignant melanoma cell, A375, was confirmed to be the most sensitive. Morphologic evaluation, cell cycle arrest and apoptosis rate analysis results showed that dicitrinone B significantly induced A375 cell apoptosis. Subsequent observation of reactive oxygen species (ROS) accumulation and mitochondrial membrane potential (MMP) reduction revealed that the apoptosis induced by dicitrinone B may be triggered by over-producing ROS. Further studies indicated that the apoptosis was associated with both intrinsic and extrinsic apoptosis pathways under the regulation of Bcl-2 family proteins. Caspase-9, caspase-8 and caspase-3 were activated during the process, leading to PARP cleavage. The pan-caspase inhibitor, Z-VAD-FMK, could reverse dicitrinone B-induced apoptosis, suggesting that it is a caspase-dependent pathway. Our data for the first time showed that dicitrinone B inhibits the proliferation of tumor cells by inducing cell apoptosis. Moreover, compared with the first-line chemotherapy drug, 5-fluorouracil (5-Fu), dicitrinone B showed much more potent anticancer efficacy, suggesting that it might serve as a potential antitumor agent.