The combination of methylsulfonylmethane and tamoxifen inhibits the Jak2/STAT5b pathway and synergistically inhibits tumor growth and metastasis in ER-positive breast cancer xenografts

Abstract

BackgroundCombination therapy, which reduces the dosage intensity of the individual drugs while increasing their efficacy, is not a novel approach for the treatment of cancer. Methylsulfonylmethane (MSM) is an organic sulfur compound shown to act against tumor cells. Tamoxifen is a commercially available therapeutic agent for breast malignancies.MethodsIn the current study, we analyzed the combinatorial effect of MSM and tamoxifen on the suppression of ER-positive breast cancer xenograft growth and metastasis. Additionally, we also validated the molecular targets by which the drug combination regulated tumor growth and metastasis.ResultsWe observed that the combination of MSM and tamoxifen regulated cell viability and migration in vitro. The intragastric administration of MSM and subcutaneous implantation of tamoxifen tablets led to tumor growth suppression and inhibition of the Janus kinase 2 (Jak2)/signal transducer and activator of transcription 5b (STAT5b) pathway. Our study also assessed the regulation of signaling molecules implicated in the growth, progression, differentiation, and migration of cancer cells, such as Jak2, STAT5b, insulin-like growth factor-1Rβ, and their phosphorylation status.ConclusionsStudy results indicated that this combination therapy inhibited tumor growth and metastasis. Therefore, this drug combination may have a synergistic and powerful anticancer effect against breast cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1445-0) contains supplementary material, which is available to authorized users.

Methylsulfonylmethane: Applications and Safety of a Novel Dietary Supplement

“…MSM has been shown to repress the expression or activities of STAT transcription factors in a number of cancer cell lines in vitro [99,100,101]. The janus kinase (Jak)/STAT pathway is involved in regulation of genes related to apoptosis, differentiation, and proliferation, all of which generate ROS as a necessary signaling component [102,103,104].…”

“…In vitro studies using MSM alone or in combination have evaluated the metabolic and phenotypic effects of a number of cancer cell lines including breast [100,101,122,123,126,181], esophagus [119], stomach [119], liver [119,120], colon [121], bladder [99], and skin cancers [123,125] with promising results. MSM independently has been shown to be cytotoxic to cancer cells by inhibiting cell viability through the induction of cell cycle arrest [119,122,123], necrosis [119], or apoptosis [100,101,119,120,121]. The inhibition of cell growth and proliferation may be attributed to the metabolic alterations induced by MSM at the transcriptional and/or post-translational stages.…”

“…The inhibition of cell growth and proliferation may be attributed to the metabolic alterations induced by MSM at the transcriptional and/or post-translational stages. For instance, MSM has been shown to inhibit expression and DNA binding of transcription factors such as STAT3 [100,101] and STAT5b [100,101,181]; meanwhile, the p53 transcription factor is maintained by MSM [100] and does not induce apoptosis [121]. Though MSM inhibition of DNA binding by STAT3 may be an indirect effect of the phosphorylation of Jak2 [99].…”

“…Though MSM inhibition of DNA binding by STAT3 may be an indirect effect of the phosphorylation of Jak2 [99]. Nonetheless, by inhibiting the binding of STAT3 and STAT5b to promoters, the reduced expression of oncogenic proteins such as vascular endothelial growth factor (VEGF) [99,100,101,123], heat shock protein (HSP)90α [100], and insulin-like growth factor-1 receptor (IGF-1R) [99,100,101] has been observed. The reduced expression of IGF-1R and VEGF may help prevent the development of tumors by reducing the insulin-like growth factor-1 (IGF-1)-mediated cell survival and proliferation pathways and preventing tumor-induced angiogenesis [182,183].…”

“…Treatment with MSM results in the induction of contact inhibition and cell senescence [122,123,125,126], anchorage-dependent growth [122,125], reduced migration of metastatic lines [101,122,125,126], and normalized wound healing [122,125]. This could in part be attributed to the robust changes to cellular filaments, including the disassembly and indirect reassembly of microtubules [123] and reorganization of actin localization [125].…”