GSK1324726A Over of all melanomas have activating BRAF mutat

Over 50% of all melanomas have activating BRAF mutations [29] and inhibition of the Ras/Raf/MEK/ERK signaling pathways is one of the most promising treatments for malignant melanoma [30]. However, studies using BRAF inhibitors have identified various feedback mechanisms to activate BRAF pathway in melanoma with the BRAF V600E mutation, which comprises over 90% of all melanoma BRAF mutations [29,31]. BRAF inhibitor resistance is not limited to melanoma, as another study showed that BRAF inhibitors increased FAK activation and the downstream Wnt/GSK-3β/β-catenin signaling pathway to promote cell proliferation in BRAF V600E colorectal cancer GSK1324726A [32]. In addition to FAK inhibitors reducing melanoma metastasis through reduction of VCAM-1 in LNs, FAK inhibitors could be used in combination with BRAF inhibitors to target BRAF V600E bearing melanomas. Cells that comprise the tumor microenvironment also play key roles in promoting metastasis [33]. Interestingly, it was shown that increased lymphangiogensis occurs prior to subsequent melanoma metastasis to LNs [19], and that this process may be driven by tumor associated macrophages. Macrophages, when cultured with B16 melanoma cells, showed increased expression of TNF-α and IL-1β, and these cytokines increased the expression of VEGF-C, an important growth factor in lymphangiogensis [9]. Cancer cells, through expression of CC chemokine receptor-7 (CCR7) then make use of the new lymphatic vessels to metastasize to LNs [34]. Overexpression of CCR7 in B16 melanoma cells enhanced metastasis to LNs and antibody neutralization of CCL21, the ligand for CCR7, reduced B16 metastasis to LNs [34]. Recent evidence has also demonstrated that FAK can alter the immune cell population of the tumor microenvironment through regulation of chemokine expression in skin cancer [35]. While we did not investigate the expression of growth factors, chemokines, or cytokines in our footpad model, we hypothesize that melanoma burdened LNs in vehicle treated mice are more inflammatory compared to the PF-271 treated group, as seen by increased size and weight of the melanoma burdened LNs and increased expression of VCAM-1 (Fig. 3, Fig. 4). Future studies are needed to better understand the other tumor-promoting roles of FAK in the tumor microenvironment.
Introduction Angiogenesis is the generation of de novo vessels from pre-existing vascular plexus commonly seen through a lifetime, providing blood nourishment of whole body tissues under physiological and pathological conditions (Baek et al., 2012; van Royen et al., 2001). There are a plethora factors and cytokines that direct the angiogenic activity of Endothelial Cells (ECs) and perivascular cells in response to various stimuli (Thal and Kishore, 2013). For instance, Vascular Endothelial Growth Factor (VEGF) as a pro-angiogenic effector was found to be useful in the modulation of angiogenesis during the onset of pathological conditions (Douglas et al., 2005; Torry et al., 1999). VEGFs isoforms act via the activation of cell surface Tyrosine Kinase receptors (RTKs), playing an inevitable role in vasculogenesis, angiogenesis. During the pro-angiogenic switch, ECs secret various enzymes to degrade the basement membrane and easily migrate into the surrounding matrix followed by proliferation, and differentiation into integrated tubular sprouts which subsequently generate functional capillary network (Risau, 1997). Such cellular events are mediated by various intracellular signal pathways. For example, Focal Adhesion Kinase (FAK) and P-38 Mitogen-Activated Protein Kinase (P-38 MAPK) were found to actively participate to switch the angiogenic potency of ECs (Qutub and Popel, 2009; Zarubin and Jiahuai, 2005). FAK, a cytoplasmic peptide with 125 kDa molecular weight and tyrosine kinase activity, plays critical role in integrin-mediated signal transductions (Chu et al., 2012). The activated FAK (p-FAK) forms a complex with Src family kinases which initiates multiple downstream signaling pathways through phosphorylation of other effectors to regulate different cellular functions (Zhao and Guan, 2011). Multiple downstream signaling pathways are identified to mediate FAK regulation in various normal and cancer cells (Lechertier and Hodivala-Dilke, 2012). An increased induction of FAK was found to exert a critical role during embryonic development and even cancer progression (Jeon et al., 2010).