br Apoptosis refers to a form
Apoptosis refers to a form of highly regulated process of physiolo-gical cell death, which evokes cell death through extrinsic (via death receptors) or intrinsic (via mitochondria) pathways. The defective apoptosis and the uncontrolled cell proliferation appear to disrupt the balance between cell division and cell death, finally leading to the development of cancer . Therefore, targeting cell apoptosis and dysfunctional cell proliferation have become a great interest for the treatment of cancer [45,46]. Apoptotic cell death is characterized by cell shrinkage, plasma membrane blebbing, nuclear condensation and ultimately DNA fragmentation . Currently, cancer cell apoptosis and cell proliferation inhibition have been shown to be the most per-vasive anti-tumor mechanism induced by many kinds of chemother-apeutic agents or antitumor drugs , and the same is true for some polysaccharides [49,50]. A previous report indicated that Angelica si-nensis polysaccharide could inhibit cell proliferation and promote the apoptosis of HeLa cells, which primarily involved the activation of the intrinsic mitochondrial pathway . Shen et al. found that APS was capable of inhibiting MKN45 cells proliferation by blocking Stearamide at G1 stage and inducing cells apoptosis in a dose- and time-dependent manner . In this study, APS failed to induce cell apoptosis and in-hibited cell proliferation, migration and invasion. Encouragingly, APS mediated CM markedly repressed the proliferation of MCF-7 cells in a time- and dose-dependent manner and induced cell cycle arrest in G1-phase. Simultaneously, we further demonstrated that CM decreased the survival of MCF-7 cells through an apoptotic mechanism, as was ver-ified by cell shrinkage, loss of microvilli, apoptotic bodies formation and nuclear fragmentation. Meanwhile, to obtain further information regarding apoptotic modulation, we examined the expression of Bax and Bcl-2 proteins in MCF-7 cells. Bcl-2 and Bax function as tumor anti-apoptotic and pro-apoptotic factors, respectively, which have been demonstrated to play crucial roles in the regulation of apoptosis, and the balance of Bax and Bcl-2, i.e. the ratio of Bax/Bcl-2, is a decisive factor for cell survival or death . Our results revealed that apoptosis was significantly stimulated as indicated by increasing the Bax/Bcl-2 ratio upon CM treatment. On this basis, APS mediated CM induced apoptosis in MCF-7 cells by modulating Bcl-2 family protein.
Cancer metastasis is a major underlying event for cancer-related morbidity and mortality . It begins with the migration and invasion of cancer cells into surrounding tissues and lymphatics followed by targeting organs. Nowadays, great attention has been paid on searching for new strategies against tumor progression, of which some poly-saccharides have shown the potential to intervene tumor cell migration and invasion [55–57]. In our study, it was reasonable to speculate that CM could suppress the migration and invasion of MCF-7 cells based on their loss of microvilli and pseudopods as one of the crucial steps in directed migration and invasion is lamellipodia formation at the leading edge of cells. Transwell assay further verified that CM possessed highly strong inhibitory eﬃcacy on cell migration and invasion, and the underlying mechanism is still to be determined in our subsequent re-search.
In conclusion, although APS did not significantly suppress the growth of MCF-7 cells in vitro, it could still be served as a triggering agent for the TNF-α and NO generation, possibly by targeting cell membrane receptor to activate macrophages. Furthermore, we de-monstrated that APS mediated CM inhibited MCF-7 cells growth in a Materials Science & Engineering C 98 (2019) 685–695
dose- and time-dependent manner, and blocked cell cycle at G1 stage. Meanwhile, CM was capable of inducing cell apoptosis by increasing the Bax/Bcl-2 ratio. Overall, apoptosis induction and cell cycle arrest may be the anti-tumor mechanisms of APS mediated CM. Currently, the eﬀorts in the study of APS are gradually shifting to prevention and clinical intervention in neoplastic disease because of its capability to enhance host immune function and its role as an adjuvant to che-motherapeutic agents. Our findings indicated that APS appeared to activate the immune response in vitro and then inhibit breast cancer cells growth, further research to evaluate the antitumor eﬀect in vivo was underway in our lab. The molecular mechanisms for macrophages activation by APS and inhibitory activity on cancer cell migration are still required for the investigations in the near future.
Appendix A. Supplementary data