The fibroblast growth factor-2 is not essential for melanoma formation in a transgenic mouse model

Riluzole prodrugs for melanoma and ALS: design, synthesis, and in vitro metabolic profiling

Riluzole (1) is an approved therapeutic for the treatment of ALS and has also demonstrated anti-melanoma activity in metabotropic glutamate GRM1 positive cell lines, a mouse xenograft assay and human clinical trials. Highly variable drug exposure following oral administration among patients, likely due to variable first pass effects from heterogeneous CYP1A2 expression, hinders its clinical use. In an effort to mitigate effects of this clearance pathway and uniformly administer riluzole at efficacious exposure levels, several classes of prodrugs of riluzole were designed, synthesized, and evaluated in multiple in vitro stability assays to predict in vivo drug levels. The optimal prodrug would possess the following profile: stability while transiting the digestive system, stability towards first pass metabolism, and metabolic lability in the plasma releasing riluzole. (S)-O-Benzyl serine derivative 9 was identified as the most promising therapeutically acceptable prodrug.

Narrowing the knowledge gaps for melanoma

Cutaneous melanoma originates from pigment producing melanocytes or their precursors and is considered the deadliest form of skin cancer. For the last 40 years, few treatment options were available for patients with late-stage melanoma. However, remarkable advances in the therapy field were made recently, leading to the approval of two new drugs, the mutant BRAF inhibitor vemurafenib and the immunostimulant ipilimumab. Although these drugs prolong patients' lives, neither drug cures the disease completely, emphasizing the need for improvements of current therapies. Our knowledge about the complex genetic and biological mechanisms leading to melanoma development has increased, but there are still gaps in our understanding of the early events of melanocyte transformation and disease progression. In this review, we present a summary of the main contributing factors leading to melanocyte transformation and discuss recent novel findings and technologies that will help answer some of the key biological melanoma questions and lay the groundwork for novel therapies.

Cellular dichotomy between anchorage-independent growth responses to bFGF and TPA reflects molecular switch in commitment to carcinogenesis

We have investigated gene expression patterns underlying reversible and irreversible anchorage-independent growth (AIG) phenotypes to identify more sensitive markers of cell transformation for studies directed at interrogating carcinogenesis responses. In JB6 mouse epidermal cells, basic fibroblast growth factor (bFGF) induces an unusually efficient and reversible AIG response, relative to 12-O-tetradecanoyl phorbol-13-acetate (TPA)-induced AIG which is irreversible. The reversible and irreversible AIG phenotypes are characterized by largely nonoverlapping global gene expression profiles. However, a subset of differentially expressed genes were identified as common to reversible and irreversible AIG phenotypes, including genes regulated in a reciprocal fashion. Hepatic leukemia factor (HLF) and D-site albumin promoter-binding protein (DBP) were increased in both bFGF and TPA soft agar colonies and selected for functional validation. Ectopic expression of human HLF and DBP in JB6 cells resulted in a marked increase in TPA- and bFGF-regulated AIG responses. HLF and DBP expression were increased in soft agar colonies arising from JB6 cells exposed to gamma radiation and in a human basal cell carcinoma tumor tissue, relative to paired nontumor tissue. Subsequent biological network analysis suggests that many of the differentially expressed genes that are common to bFGF- and TPA-dependent AIG are regulated by c-Myc, SP-1, and HNF-4 transcription factors. Collectively, we have identified a potential molecular switch that mediates the transition from reversible to irreversible AIG.

The 18 kDa isoform of basic fibroblast growth factor is sufficient to stimulate human melanoma growth and angiogenesis

Basic fibroblast growth factor is the best-characterized autocrine growth factor in melanoma development and progression. We hypothesized that basic fibroblast growth factor might induce a more aggressive phenotype dependent on the amount of protein expressed in melanoma. Two human melanoma cell lines, M14 and 1F6, known to have low endogenous basic fibroblast growth factor expression and slow growth as subcutaneous xenografts, were stably transfected with vectors encoding either the 18 kDa or all (ALL) isoform proteins of human basic fibroblast growth factor. Different clones overexpressing the 18 kDa or ALL basic fibroblast growth factor proteins were easily obtained. Increased levels of basic fibroblast growth factor were secreted in conditioned medium and stored on the extracellular membrane. Biological activity of the overexpressed basic fibroblast growth factor was confirmed in a human umbilical vein endothelial cell proliferation assay. In 1F6 cells, overexpression of either 18 kDa or ALL basic fibroblast growth factor proteins resulted in up to two-fold shorter in-vitro doubling times (P<0.05). In addition, in vivo, both 18 kDa and ALL basic fibroblast growth factor-overexpressing 1F6 subcutaneous xenografts displayed significantly higher growth rates (P<0.05). In contrast, no major differences in in-vitro and in-vivo doubling times were observed when 18 kDa or ALL isoforms of basic fibroblast growth factor were overexpressed in M14 cells. Interestingly, basic fibroblast growth factor overexpression only affected the microvasculature in 1F6 xenografts. Although blood vessels in 1F6 parent tumors were large, 1F6 tumors overexpressing basic fibroblast growth factor contained numerous small, compressed vessels. Taken together, overexpression of the 18 kDa basic fibroblast growth factor protein only can promote autocrine melanoma cell growth and paracrine-driven angiogenesis.