RAS/RAF/MEK/ERK and PI3K/PTEN/AKT Signaling in Malignant Melanoma Progression and Therapy

Cutaneous malignant melanoma is one of the most serious skin cancers and is highly invasive and markedly resistant to conventional therapy. Melanomagenesis is initially triggered by environmental agents including ultraviolet (UV), which induces genetic/epigenetic alterations in the chromosomes of melanocytes. In human melanomas, the RAS/RAF/MEK/ERK (MAPK) and the PI3K/PTEN/AKT (AKT) signaling pathways are two major signaling pathways and are constitutively activated through genetic alterations. Mutations of RAF, RAS, and PTEN contribute to antiapoptosis, abnormal proliferation, angiogenesis, and invasion for melanoma development and progression. To find better approaches to therapies for patients, understanding these MAPK and AKT signaling mechanisms of melanoma development and progression is important. Here, we review MAPK and AKT signaling networks associated with melanoma development and progression

Molecular Network Associated with MITF in Skin Melanoma Development and Progression

Various environmental and genetic factors affect the development and progression of skin cancers including melanoma. Melanoma development is initially triggered by environmental factors including ultraviolet (UV) light, and then genetic/epigenetic alterations occur in skin melanocytes. These first triggers alter the conditions of numerous genes and proteins, and they induce and/or reduce gene expression and activate and/or repress protein stability and activity, resulting in melanoma progression. Microphthalmia-associated transcription factor (MITF) is a master regulator gene of melanocyte development and differentiation and is also associated with melanoma development and progression. To find better approaches to molecular-based therapies for patients, understanding MITF function in skin melanoma development and progression is important. Here, we review the molecular networks associated with MITF in skin melanoma development and progression

Barium Promotes Anchorage-Independent Growth and Invasion of Human HaCaT Keratinocytes via Activation of c-SRC Kinase

Explosive increases in skin cancers have been reported in more than 36 million patients with arsenicosis caused by drinking arsenic-polluted well water. This study and previous studies showed high levels of barium as well as arsenic in the well water. However, there have been no reports showing a correlation between barium and cancer. In this study, we examined whether barium (BaCl2) may independently have cancer-related effects on human precancerous keratinocytes (HaCaT). Barium (5–50 µM) biologically promoted anchorage-independent growth and invasion of HaCaT cells in vitro. Barium (5 µM) biochemically enhanced activities of c-SRC, FAK, ERK and MT1-MMP molecules, which regulate anchorage-independent growth and/or invasion. A SRC kinase specific inhibitor, protein phosphatase 2 (PP2), blocked barium-mediated promotion of anchorage-independent growth and invasion with decreased c-SRC kinase activity. Barium (2.5–5 µM) also promoted anchorage-independent growth and invasion of fibroblasts (NIH3T3) and immortalized nontumorigenic melanocytes (melan-a), but not transformed cutaneous squamous cell carcinoma (HSC5 and A431) and malignant melanoma (Mel-ret) cells, with activation of c-SRC kinase. Taken together, our biological and biochemical findings newly suggest that the levels of barium shown in drinking well water independently has the cancer-promoting effects on precancerous keratinocytes, fibroblast and melanocytes in vitro

Bidirectional functions of arsenic as a carcinogen and an anti-cancer agent in human squamous cell carcinoma.

Bidirectional cancer-promoting and anti-cancer effects of arsenic for cancer cells have been revealed in previous studies. However, each of these effects (cancer-promoting or anti-cancer) was found in different cells at different treated-concentration of arsenic. In this study, we for the first time indicated that arsenic at concentration of 3 µM, equal to average concentration in drinking water in cancer-prone areas in Bangladesh, simultaneously expressed its bidirectional effects on human squamous cell carcinoma HSC5 cells with distinct pathways. Treatment with 3 µM of arsenic promoted cell invasion via upregulation of expression of MT1-MMP and downregulation of expression of p14ARF and simultaneously induced cell apoptosis through inhibition of expression of N-cadherin and increase of expression of p21(WAF1/CIP1) at both transcript and protein levels in HSC5 cells. We also showed that inhibition of MT1-MMP expression by NSC405020 resulted in decrease of arsenic-mediated invasion of HSC5 cells involving decrease in phosphorylated extracellular signal-regulated kinases (pERK). Taken together, our biological and biochemical findings suggested that arsenic expressed bidirectional effects as a carcinogen and an anti-cancer agent in human squamous cell carcinoma HSC5 cells with distinct pathways. Our results might play an important scientific evident for further studies to find out a better way in treatment of arsenic-induced cancers, especially in squamous cell carcinoma

MT1-MMP and P14 transcript and protein expression levels in HSC5 cells treated with arsenic.

<p>A and C) transcript expression levels of MT1-MMP and p14 were measured by real-time PCR. **, significantly different (p<0.01) from the control by Student's t-test. B and D) Protein expression levels of MT1-MMP and p14 were measured by immunoblot. TUBULIN was used as a positive control. Three independent experiments were performed and the same results were obtained.</p

Effects of arsenic on apoptosis of HSC5 cells.

<p>Viability of HSC5 cells treated with 0, 1.0, 3.0 and 5.0 µM of arsenic was evaluated by crystal violet (CV). Cells were presented in photographs (A) and ratios of arsenic treated live cells and control live cells were presented in a graph (B). **, Significantly different (p<0.01) from the control by the Student's t-test.</p

Effects of arsenic on invasion of HSC5 cells.

<p>Invasive ability of of HSC5 cells treated 0, 1.0, 3.0 and 5.0 µM of arsenic were evaluated by invasion assay. Number of invading HSC5 cells treated with arsenic in the invasion assay were presented in photographs (A) and a graph (B). **, Significantly different (p<0.01) from the control by the Student's t-test.</p

N-cadherin and p21 transcript and protein expression levels in HSC5 cells treated with arsenic.

<p>A and C) transcript expression levels of N-cadherin and p21 were measured by real-time PCR. ***, significantly different (p<0.001) from the control by Student's t-test. B and D) Protein expression levels of N-cadherin and p21 were measured by immunoblot. TUBULIN was used as a positive control. Three independent experiments were performed and the same results were obtained.</p

Effects of arsenic on invasive activity and phosphorylation and/or expression levels of MT1-MMP and ERK 4 in HSC5 cells.

<p>A), Invasive activity of HSC5 treated with 3 µM of arsenic was evaluated invasion assay. Level of invasive ability is presented as number of invading cells in a graph (left) and photographs (right). **, Significantly different (p<0.01) from the control by the Student's t-test. Phosphorylated levels of ERK (P-ERK) and protein expression levels of MT1-MMP and ERK in HSC5 cells treated with 3 µM arsenic for 24 hours are presented. TUBULIN protein expression levels are presented as an internal control.</p