Gβγ subunits inhibit Epac-induced melanoma cell migration

<p>Abstract</p> <p>Background</p> <p>Recently we reported that activation of Epac1, an exchange protein activated by cAMP, increases melanoma cell migration via Ca ²⁺release from the endoplasmic reticulum (ER). G-protein βγ subunits (Gβγ) are known to act as an independent signaling molecule upon activation of G-protein coupled receptor. However, the role of Gβγ in cell migration and Ca ²⁺signaling in melanoma has not been well studied. Here we report that there is crosstalk of Ca ²⁺signaling between Gβγ and Epac in melanoma, which plays a role in regulation of cell migration.</p> <p>Methods</p> <p>SK-Mel-2 cells, a human metastatic melanoma cell line, were mainly used in this study. Intracellular Ca ²⁺was measured with Fluo-4AM fluorescent dyes. Cell migration was examined using the Boyden chambers.</p> <p>Results</p> <p>The effect of Gβγ on Epac-induced cell migration was first examined. Epac-induced cell migration was inhibited by mSIRK, a Gβγ -activating peptide, but not its inactive analog, L9A, in SK-Mel-2 cells. Guanosine 5', α-β-methylene triphosphate (Gp(CH2)pp), a constitutively active GTP analogue that activates Gβγ, also inhibited Epac-induced cell migration. In addition, co-overexpression of β1 and γ2, which is the major combination of Gβγ, inhibited Epac1-induced cell migration. By contrast, when the C-terminus of β adrenergic receptor kinase (βARK-CT), an endogenous inhibitor for Gβγ, was overexpressed, mSIRK's inhibitory effect on Epac-induced cell migration was negated, suggesting the specificity of mSIRK for Gβγ. We next examined the effect of mSIRK on Epac-induced Ca ²⁺response. When cells were pretreated with mSIRK, but not with L9A, 8-(4-Methoxyphenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate (8-pMeOPT), an Epac-specific agonist, failed to increase Ca ²⁺signal. Co-overexpression of β1 and γ2 subunits inhibited 8-pMeOPT-induced Ca ²⁺elevation. Inhibition of Gβγ with βARK-CT or guanosine 5'-O-(2-thiodiphosphate) (GDPβS), a GDP analogue that inactivates Gβγ, restored 8-pMeOPT-induced Ca ²⁺elevation even in the presence of mSIRK. These data suggested that Gβγ inhibits Epac-induced Ca ²⁺elevation. Subsequently, the mechanism by which Gβγ inhibits Epac-induced Ca ²⁺elevation was explored. mSIRK activates Ca ²⁺influx from the extracellular space. In addition, W-5, an inhibitor of calmodulin, abolished mSIRK's inhibitory effects on Epac-induced Ca ²⁺elevation, and cell migration. These data suggest that, the mSIRK-induced Ca ²⁺from the extracellular space inhibits the Epac-induced Ca ²⁺release from the ER, resulting suppression of cell migration.</p> <p>Conclusion</p> <p>We found the cross talk of Ca ²⁺signaling between Gβγ and Epac, which plays a major role in melanoma cell migration.</p

Riluzole exerts distinct antitumor effects from a metabotropic glutamate receptor 1-specific inhibitor on breast cancer cells

Recent evidence suggests that glutamate signaling plays an important role in cancer. Riluzole is a glutamate release inhibitor and FDA-approved drug for the treatment of amyotrophic lateral sclerosis. It has been investigated as an inhibitor of cancer cell growth and tumorigenesis with the intention of repurposing it for the treatment of cancer. Riluzole is thought to act by indirectly inhibiting glutamate signaling. However, the specific effects of riluzole in breast cancer cells are not well understood. In this study, the anti-cancer effects of riluzole were explored in a panel of breast cancer cell lines in comparison to the metabotropic glutamate receptor 1-specific inhibitor BAY 36-7620. While both drugs inhibited breast cancer cell proliferation, there were distinct functional effects suggesting that riluzole action may be metabotropic glutamate receptor 1-independent. Riluzole induced mitotic arrest independent of oxidative stress while BAY 36-7620 had no measurable effect on mitosis. BAY 36-7620 had a more pronounced and significant effect on DNA damage than riluzole. Riluzole altered cellular metabolism as demonstrated by changes in oxidative phosphorylation and cellular metabolite levels. These results provide a better understanding of the functional action of riluzole in the treatment of breast cancer

The transcription factor RUNX2 regulates receptor tyrosine kinase expression in melanoma.

Receptor tyrosine kinases-based autocrine loops largely contribute to activate the MAPK and PI3K/AKT pathways in melanoma. However, the molecular mechanisms involved in generating these autocrine loops are still largely unknown. In the present study, we examine the role of the transcription factor RUNX2 in the regulation of receptor tyrosine kinase (RTK) expression in melanoma. We have demonstrated that RUNX2-deficient melanoma cells display a significant decrease in three receptor tyrosine kinases, EGFR, IGF-1R and PDGFRβ. In addition, we found co-expression of RUNX2 and another RTK, AXL, in both melanoma cells and melanoma patient samples. We observed a decrease in phosphoAKT2 (S474) and phosphoAKT (T308) levels when RUNX2 knock down resulted in significant RTK down regulation. Finally, we showed a dramatic up regulation of RUNX2 expression with concomitant up-regulation of EGFR, IGF-1R and AXL in melanoma cells resistant to the BRAF V600E inhibitor PLX4720. Taken together, our results strongly suggest that RUNX2 might be a key player in RTK-based autocrine loops and a mediator of resistance to BRAF V600E inhibitors involving RTK up regulation in melanoma

Frontiers in Pigment Cell and Melanoma Research

We identify emerging frontiers in clinical and basic research of melanocyte biology and its associated biomedical disciplines. We describe challenges and opportunities in clinical and basic research of normal and diseased melanocytes that impact current approaches to research in melanoma and the dermatological sciences. We focus on four themes: (1) clinical melanoma research, (2) basic melanoma research, (3) clinical dermatology, and (4) basic pigment cell research, with the goal of outlining current highlights, challenges, and frontiers associated with pigmentation and melanocyte biology. Significantly, this document encapsulates important advances in melanocyte and melanoma research including emerging frontiers in melanoma immunotherapy, medical and surgical oncology, dermatology, vitiligo, albinism, genomics and systems biology, epidemiology, pigment biophysics and chemistry, and evolution

Clinical actionability of comprehensive genomic profiling for management of rare or refractory cancers

Background. The frequency with which targeted tumor sequencing results will lead to implemented change in care is unclear. Prospective assessment of the feasibility and limitations of using genomic sequencing is critically important. Methods. A prospective clinical study was conducted on 100 patients with diverse-histology, rare, or poor-prognosis cancers to evaluate the clinical actionability of a Clinical Laboratory Improvement Amendments (CLIA)-certified, comprehensive genomic profiling assay (FoundationOne), using formalin-fixed, paraffin-embedded tumors. The primary objectives were to assess utility, feasibility, and limitations of genomic sequencing for genomically guided therapy or other clinical purpose in the setting of a multidisciplinary molecular tumor board. Results. Of the tumors from the 92 patients with sufficient tissue, 88 (96%) had at least one genomic alteration (average 3.6, range 0–10). Commonly altered pathways included p53 (46%), RAS/RAF/MAPK (rat sarcoma; rapidly accelerated fibrosarcoma; mitogen-activated protein kinase) (45%), receptor tyrosine kinases/ligand (44%), PI3K/AKT/mTOR (phosphatidylinositol-4,5-bisphosphate 3-kinase; protein kinase B; mammalian target of rapamycin) (35%), transcription factors/regulators (31%), and cell cycle regulators (30%). Many low frequency but potentially actionable alterations were identified in diverse histologies. Use of comprehensive profiling led to implementable clinical action in 35% of tumors with genomic alterations, including genomically guided therapy, diagnostic modification, and trigger for germline genetic testing. Conclusion. Use of targeted next-generation sequencing in the setting of an institutional molecular tumor board led to implementable clinical action in more than one third of patients with rare and poor-prognosis cancers. Major barriers to implementation of genomically guided therapy were clinical status of the patient and drug access. Early and serial sequencing in the clinical course and expanded access to genomically guided early-phase clinical trials and targeted agents may increase actionability. Implications for Practice: Identification of key factors that facilitate use of genomic tumor testing results and implementation of genomically guided therapy may lead to enhanced benefit for patients with rare or difficult to treat cancers. Clinical use of a targeted next-generation sequencing assay in the setting of an institutional molecular tumor board led to implementable clinical action in over one third of patients with rare and poor prognosis cancers. The major barriers to implementation of genomically guided therapy were clinical status of the patient and drug access both on trial and off label. Approaches to increase actionability include early and serial sequencing in the clinical course and expanded access to genomically guided early phase clinical trials and targeted agents

Anatomical distribution analysis reveals lack of Langerin+ dermal dendritic cells in footpads and tail of C57BL/6 mice.

Epidermal Langerhans cells (LCs) and dermal dendritic cells (dDCs) capture cutaneous antigens and present them to T-cells in lymph nodes (LNs). The function of LCs and Langerin+ dDCs was extensively studied in the mouse, but their anatomical repartition is unknown. Here, we found LCs in back skin, footpads and tail skin of C57BL/6, BALB/c, 129/Sv and CBA/J mice. Langerin+ dDCs were readily observed in back skin of all strains, but only in footpads and tail of BALB/c and CBA/J mice. Similarly, while LCs were equally present in all LNs and strains, Langerin+ dDCs were found in popliteal LNs (draining footpads) only in BALB/c and CBA/J mice. The sciatic LNs, which we identified as the major tail-draining lymphoid organ, were devoid of Langerin+ dDCs in all strains. Thus, functionally different DCs reside in different skin areas, with variations among mouse strains, implying a potential impact on the cutaneous immune reaction.letterresearch support, non-u.s. gov't2014 Mayimporte