lde225 and Melanoma

Medications in dermatology are used in a variety of different methods and dosages and for numerous different diseases entities that are not approved by the US Food and Drug Administration (FDA); however, there are medications that have only recently hit the market that require our attention, as they are either FDA approved for the intended dermatologic use or could be effective in treating conditions that previously have been poorly managed.

Topics: Aminolevulinic Acid; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Antineoplastic Agents; Arthritis, Psoriatic; Azetidines; Biphenyl Compounds; Carcinoma, Basal Cell; Cosmetic Techniques; Deoxycholic Acid; Dermatologic Agents; Drug Approval; Facial Dermatoses; Humans; Keratosis, Actinic; Melanoma; Oncolytic Virotherapy; Piperidines; Psoriasis; Pyridines; Scalp Dermatoses; Skin Neoplasms; United States; United States Food and Drug Administration

Control of BRAF(V600E) metastatic melanoma by BRAF inhibitor (BRAF-I) is limited by intrinsic and acquired resistance. Growth factor receptor up-regulation is among the mechanisms underlying BRAF-I resistance of melanoma cells. Here we demonstrate for the first time that PDGFRα up-regulation causes BRAF-I resistance. PDGFRα inhibition by PDGFRα-specific short hairpin (sh)RNA and by PDGFRα inhibitors restores and increases melanoma cells' sensitivity to BRAF-I in vitro and in vivo. This effect reflects the inhibition of ERK and AKT activation which is associated with BRAF-I resistance of melanoma cells. PDGFRα up-regulation is mediated by Sonic Hedgehog Homolog (Shh) pathway activation which is induced by BRAF-I treatment. Similarly to PDGFRα inhibition, Shh inhibition by LDE225 restores and increases melanoma cells' sensitivity to BRAF-I. These effects are mediated by PDGFRα down-regulation and by ERK and AKT inhibition. The clinical relevance of these data is indicated by the association of PDGFRα up-regulation in melanoma matched biopsies of BRAF-I +/- MEK inhibitor treated patients with shorter time to disease progression and less tumor regression. These findings suggest that monitoring patients for early PDGFRα up-regulation will facilitate the identification of those who may benefit from the treatment with BRAF-I in combination with clinically approved PDGFRα or Shh inhibitors.

Topics: Animals; Antineoplastic Agents; Benzamides; Benzimidazoles; Biphenyl Compounds; Cell Line, Tumor; Drug Resistance, Neoplasm; Extracellular Signal-Regulated MAP Kinases; Gene Silencing; Hedgehog Proteins; Humans; Imatinib Mesylate; Indoles; MAP Kinase Signaling System; Melanoma; Mice; Piperazines; Piperidines; Protein Kinase Inhibitors; Proto-Oncogene Proteins B-raf; Proto-Oncogene Proteins c-akt; Pyridines; Pyrimidines; Pyrroles; Receptor, Platelet-Derived Growth Factor alpha; RNA, Small Interfering; Sulfonamides; Sunitinib; Up-Regulation; Vemurafenib

Melanoma is one of the most aggressive cancers and its incidence is increasing worldwide. So far there are no curable therapies especially after metastasis. Due to frequent mutations in members of the mitogen-activated protein kinase (MAPK) signaling pathway, this pathway is constitutively active in melanoma. It has been shown that the SONIC HEDGEHOG (SHH)-GLI and MAPK signaling pathway regulate cell growth in many tumors including melanoma and interact with each other in the regulation of cell proliferation and survival. Here we show that the SHH-GLI pathway is active in human melanoma cell lines as they express downstream target of this pathway GLI1. Expression of GLI1 was significantly higher in human primary melanoma tissues harboring BRAF(V600E) mutation than those with wild type BRAF. Pharmacologic inhibition of BRAF(V600E) in human melanoma cell lines resulted in decreased expression of GLI1 thus demonstrating interaction of SHH-GLI and MAPK pathways. Inhibition of SHH-GLI pathway by the novel small molecule inhibitor of smoothened NVP-LDE225 was followed by inhibition of cell growth and induction of apoptosis in human melanoma cell lines, interestingly with both BRAF(V600E) and BRAF(Wild Type) status. NVP-LDE225 was potent in reducing cell proliferation and inducing tumor growth arrest in vitro and in vivo, respectively and these effects were superior to the natural compound cyclopamine. Finally, we conclude that inhibition of SHH-GLI signaling pathway in human melanoma by the specific smoothened inhibitor NVP-LDE225 could have potential therapeutic application in human melanoma even in the absence of BRAF(V600E) mutation and warrants further investigations.

Topics: Animals; Antineoplastic Agents; Apoptosis; Biphenyl Compounds; Cell Line, Tumor; Cell Proliferation; Cell Survival; Disease Models, Animal; Female; G1 Phase Cell Cycle Checkpoints; Gene Expression Regulation, Neoplastic; Hedgehog Proteins; Humans; Indoles; Melanoma; Mice; Mutation; Proto-Oncogene Proteins B-raf; Pyridines; Receptors, G-Protein-Coupled; Signal Transduction; Smoothened Receptor; Sulfonamides; Transcription Factors; Tumor Burden; Vemurafenib; Xenograft Model Antitumor Assays; Zinc Finger Protein GLI1