Breast cancer is the second most common cancer in women. The roles of the SIRT and FoxO proteins in tumor progression are known, but their roles in metastasis have not yet been clearly elucidated. In our study, we investigated the roles of SIRT and FoxO proteins their downstream pathways, proteins p21 and p53, in tumor progression and metastasis. We evaluated these proteins in vitro using metastatic 4TLM and 67NR cell lines, as well as their expression levels in tumor-bearing mice. In addition, the regulatory role of SIRT and FoxO proteins in different transduction cascades was examined by IPA core analysis, and clinicopathological evidence was investigated in the TCGA database. In primary tumors, the expression levels of SIRT1, p21, p53, E2F1 and FoxO proteins were higher in 67NR groups. In metastatic tissues, the expression levels of SIRT1, E2F1 and FoxO proteins were found to be enhanced, whereas the levels of p53 and p21 expression were noted to be reduced. IPA analysis also provided empirical evidence of the mechanistic involvement of SIRT and FoxO proteins in tumor progression and metastasis. In conclusion, SIRT1 was found to co-operate with FoxO proteins and to play a critical role in metastasis. Additional research is required to determine why overexpression of SIRT1 in metastatic tissues has oncogenic effects.

The goal of this study was to mechanistically analyze the effects of pre-treatment or post-treatment melatonin on the metastatic spread in a mice model. Consequently, the effects on the tumor growth, angiogenesis and metastasis were evaluated with immunohistochemical and western blot analysis. 8–10 weeks-old female BALB/c mice (n = 60, 10/group) were used. Liver metastatic cells (4TLM) from 4T1 murine breast carcinoma were previously isolated. Melatonin was administrated either before or after the injection of 4TLM cells into the mammary pad. Tumor and vehicle (%6 ethanol) injections were given to vehicle groups. Tumor group consisted of the mice injected with only 4TLM cells injected to tumor group and no intervention to control group. Necropsies were performed 27 days after injection of 4TLM. Primary tumors and metastatic tissues were removed. Furthermore, changes in lung and liver metastasis and primary tumor growth and angiogenesis were evaluated. In our study neutrophil levels were noted to be increased in peripheral blood of the tumor-bearing mice. Melatonin exerted inhibitory effects on the 4TLM-induced leukocytosis. Melatonin significantly decreased lung and liver metastasis, primary tumor growth and angiogenesis. The results demonstrated that melatonin might have a therapeutic role through reducing systemic inflammatory responses, metastasis, tumor growth and angiogenesis.