Deacetylated GM3 Promotes uPAR-Associated Membrane Molecular Complex to Activate p38 MAPK in Metastatic Melanoma

Abstract

GM3, the simplest ganglioside, regulates cell proliferation, migration, and invasion by influencing cell signaling at the membrane level. Although the classic N-acetylated form of GM3 (NeuAcLacCer) is commonly expressed and has been well studied, deacetylated GM3 (NeuNH 2 LacCer, d-GM3) has been poorly investigated, despite its presence in metastatic tumors but not in noninvasive melanomas or benign nevi. We have recently found that d-GM3 stimulates cell migration and invasion by activating urokinase plasminogen activator receptor (uPAR) signaling to augment matrix metalloproteinase-2 (MMP-2) function. However, the mechanisms by which d-GM3/ uPAR increase MMP-2 expression and activation are not clear. By modifying the expression of d-GM3 genetically and biochemically, we found that decreasing d-GM3 expression inhibits, whereas overexpressing d-GM3 stimulates, p38 mitogen-activated protein kinase (MAPK) activity to influence MMP-2 expression and activation. p38 MAPK (p38) activation requires the formation of a membrane complex that contains uPAR, caveolin-1, and integrin a5b1 in membrane lipid rafts. In addition, knocking down or inhibiting focal adhesion kinase (FAK), phosphoinositide 3-kinase (PI3K), or Src kinase significantly reduces d-GM3-induced p38 phosphorylation and activation. Taken together, these results suggest that d-GM3 enhances the metastatic phenotype by activating p38 signaling through uPAR/integrin signaling with FAK, PI3K, and Src kinase as intermediates. Elucidation of the mechanisms by which d-GM3, a newly discovered, potential biomarker of metastatic melanomas, promotes cell metastasis will help us to understand the function of d-GM3 in metastatic melanomas and may lead to novel GM3-based cancer therapies. Mol Cancer Res; 11(6); 665-75. Ó2013 AACR. IntroductionAlthough recent therapeutic progress for metastatic melanomas has significantly improved, including the more recent availability of small-molecule inhibitors targeting BRAF mutation or both BRAF mutation and MEK, or anti-CTLA4 antibody, survival is minimally prolonged and mortality rate of metastatic melanomas remains high (1-3). It is of utmost importance to discover specific molecular biomarkers that can distinguish melanomas with metastatic propensity from more indolent ones, which will improve prognostication, allow for earlier and more efficacious treatments, and provide additional targets for novel therapy.

Toward Repurposing Metformin as a Precision Anti-Cancer Therapy Using Structural Systems Pharmacology

“…A different study on Metformin’s effect on human epidermoid carcinoma, shows a similar decrease in the activation of MAPK14 33 with a suppressive effect on cancer cell proliferation; another study, shows that Metformin directly decreases the phosphorylation levels of MAPK14 in bovine granulosa cells 35 , a third study shows that Metformin, used in conjunction with gefitinib, decreased levels of MSH2 protein in human lung squamous cell carcinoma, again, through down regulation of MAPK14 34 . Finally, a study on metastatic melanomas shows that activation of MAPK14 by urokinase plasminogen activator receptor (uPAR) clustering on cell surfaces (promoted by d-GM3, a ganglioside) results in the activation of matrix metalloproteinase-2 (MMP-2) 36 which contributes to cell migration and metastasis in cancer cells. This supports our findings with regards to MAPK14 as a putative target of Metformin, and provides some justification for Metformin’s purported anti-cancer activity.…”

Steroid Receptor RNA Activator, a Long Noncoding RNA, Activates p38, Facilitates Epithelial-Mesenchymal Transformation, and Mediates Experimental Melanoma Metastasis

“…Puujalka et al (2016) reported that from 22 melanoma cell lines, predominant p38 over c-Jun N-terminal kinase signaling results in a VEGF-C high /MITF low phenotype, leading to a highly mobile and metastatic melanoma. GM3, the simplest ganglioside, enhances melanoma metastasis by activating p38 through integrin signaling associated with FAK, PI3K, and Src kinase (Yan et al, 2013). In contrast, the RAS/RAF/MEK/ERK pathway is also important in melanoma progression and metastasis, as evidenced by the clinical significance of B-Raf or MEK inhibitors in treating BRAFmutant metastatic melanoma (Dossett et al, 2015).…”

Targeting of tumor-associated gangliosides with antibodies affects signaling pathways and leads to cell death including apoptosis

“…In 2013, Yan et al elucidated mechanism regulating migration and invasion of melanoma cells stimulated with deacetylated GM3. Here, over-expression of the ganglioside caused MMP-2 activation via P38 action, with involvement of lipid membrane raft-associated complexes of uPAR, caveolin-1 and a5b1 integrin, and FAK, PI3K, SRC signaling networks [29]. Tumor-associated gangliosides are also shed to microenvironment and detected in sera of cancer patients.…”