In one metastatic sample originating from main NM, we observed a second, top p-RSK1 band that we hypothesize might relate to multiple phosphorylation claims of RSK1 with this specimen. proliferation is definitely more sensitive to protein S6 kinase, 90 kDa, polypeptide 1 knockdown/inhibition than is definitely superficial distributing melanoma cell proliferation. Treating an additional nodular melanoma cell collection, WM 1366, with BI-D1870 induces a dose-dependent reduction in cell proliferation. DMSO, dimethyl sulfoxide. mmc3.pdf (231K) GUID:?3C485BD0-06BB-4D73-B203-3EE070EE9E0A Supplemental Table S1 mmc4.docx (95K) GUID:?5AE36418-DFE3-4AC4-9F7E-D894D94A52C1 Supplemental Table S2 mmc5.docx (24K) GUID:?1453DE10-687B-4C9E-A8E1-C696CCE62496 Supplemental Table S3 mmc6.docx (454K) GUID:?06181434-8478-4F6C-BE1F-6C14F34B6721 Abstract The two major melanoma histologic subtypes, superficial spreading and nodular melanomas, differ in their rate of dermal invasion but converge biologically once they invade and metastasize. Herein, we tested the hypothesis that unique molecular alterations arising in main melanoma cells might persist as these tumors progress to invasion and metastasis. Ribosomal protein S6 kinase, 90 kDa, polypeptide 1 (RSK1; established name RPS6KA1) was significantly hyperactivated in human being melanoma lines and metastatic cells derived from nodular compared with superficial distributing melanoma. RSK1 was constitutively phosphorylated at Ser-380 in nodular but not superficial distributing melanoma and did not directly correlate with BRAF or MEK activation. Nodular melanoma cells were more sensitive to RSK1 inhibition using siRNA and the pharmacological inhibitor BI-D1870 compared with superficial distributing cells. Gene manifestation microarray analyses exposed that RSK1 orchestrated a program of gene manifestation that advertised cell motility and invasion. Differential overexpression of the prometastatic matrix metalloproteinase 8 and cells inhibitor of metalloproteinases 1 in metastatic nodular compared with metastatic superficial distributing melanoma was observed. Finally, using an zebrafish model, constitutive RSK1 activation improved melanoma invasion. Collectively, these data reveal a novel role for triggered RSK1 in the progression of nodular melanoma and suggest that melanoma originating from different histologic subtypes may be biologically unique and that these variations are managed as the tumors invade and metastasize. Superficial distributing melanoma Everolimus (RAD001) (SSM) and nodular melanoma (NM) represent the two most common main melanoma histologic subtypes, accounting for 70% and 15% to 20% of instances, respectively.1,2 SSM is characterized by a radial growth phase (RGP) consisting of an intraepidermal component. Whereas SSM can proceed from a RGP to a vertical growth phase (VGP) and finally to distant metastases, NM develops rapidly in a vertical manner (VGP), AKT with no horizontal growth phase.3 To date, the prognostic and therapeutic impact of melanoma histologic subtypes has been relatively limited. The American Joint Committee on Malignancy staging system uses tumor thickness, ulceration, mitotic index, and lymph node status, but not histologic subtype, in the recurrence/metastasis risk assessment of patients with main localized melanoma.4 This is, in part, due to the current linear model of melanoma progression, which dictates that melanoma begins with the transformation of epidermal melanocytes and an initial RGP, followed by a subsequent transition to a VGP and distant metastasis.5C7 Hence, it is generally accepted that this velocity of dermal invasion is the only aspect that differentiates the NM and SSM subtypes. Recent discoveries in other solid tumor types emphasize the potential role of histology-driven molecular characterization to assist in the diagnosis and treatment of malignancy.8C11 Indeed, the power of histologic classification in melanoma has been demonstrated with acral lentiginous melanoma, which composes approximately 10% of main Everolimus (RAD001) melanomas. The prevalence of molecular alterations in the c-KIT oncogene in this histologic melanoma subtype has defined acral lentiginous melanoma as a distinct and useful subclassification of melanoma, and a phase 2 trial of the c-KIT inhibitor imatinib validated the rationale of subtype-specific therapy for this group of melanoma patients.12 In contrast, the clinical relevance of the SSM and NM subtypes has been largely overlooked. Recent reports by our groups as well Everolimus (RAD001) as others suggest that main SSM and NM might be unique biological entities.13C19 Unbiased, high-throughput genetic techniques, such as comparative genomic hybridization, single nucleotide polymorphism arrays, and microarrays, have revealed the presence of recurrent SSM-specific deletions that are present or even amplified in NM and, thus, cannot be reconciled with the linear progression model, even when epigenetic modifications are taken into account. Similarly, significant alterations in mRNA and miRNA gene expression are observed when comparing SSM with nevi and NM, and these alterations cannot be explained by the existing stepwise (linear) model.16,17 Together, these findings suggest that distinct molecular alterations between SSM and NM might underlie the biological differences between these subtypes. However, it is unclear whether differences that exist between main SSM and NM are.
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