plx-4720 and Neoplasm-Metastasis

While response rates to BRAF inhibitiors (BRAFi) are high, disease progression emerges quickly. One strategy to delay the onset of resistance is to target anti-apoptotic proteins such as BCL-2, known to be associated with a poor prognosis. We analyzed BCL-2 family member expression levels of 34 samples from 17 patients collected before and 10 to 14 days after treatment initiation with either vemurafenib or dabrafenib/trametinib combination. The observed changes in mRNA and protein levels with BRAFi treatment led us to hypothesize that combining BRAFi with a BCL-2 inhibitor (the BH3-mimetic navitoclax) would improve outcome. We tested this hypothesis in cell lines and in mice. Pretreatment mRNA levels of BCL-2 negatively correlated with maximal tumor regression. Early increases in mRNA levels were seen in BIM, BCL-XL, BID and BCL2-W, as were decreases in MCL-1 and BCL2A. No significant changes were observed with BCL-2. Using reverse phase protein array (RPPA), significant increases in protein levels were found in BIM and BID. No changes in mRNA or protein correlated with response. Concurrent BRAF (PLX4720) and BCL2 (navitoclax) inhibition synergistically reduced viability in BRAF mutant cell lines and correlated with down-modulation of MCL-1 and BIM induction after PLX4720 treatment. In xenograft models, navitoclax enhanced the efficacy of PLX4720. The combination of a selective BRAF inhibitor with a BH3-mimetic promises to be an important therapeutic strategy capable of enhancing the clinical efficacy of BRAF inhibition in many patients that might otherwise succumb quickly to de novo resistance. Trial registrations: ClinicalTrials.gov NCT01006980; ClinicalTrials.gov NCT01107418; ClinicalTrials.gov NCT01264380; ClinicalTrials.gov NCT01248936; ClinicalTrials.gov NCT00949702; ClinicalTrials.gov NCT01072175.

Topics: Adult; Aged; Aniline Compounds; Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Line, Tumor; Drug Resistance, Neoplasm; Humans; Imidazoles; Indoles; Melanoma; Mice; Middle Aged; Mutation, Missense; Neoplasm Metastasis; Oximes; Proto-Oncogene Proteins B-raf; Proto-Oncogene Proteins c-bcl-2; Pyridones; Pyrimidinones; Sulfonamides; Vemurafenib

Melanoma is a highly metastatic and lethal form of skin cancer. The protein kinase BRAF is mutated in about 40% of melanomas, and BRAF inhibitors improve progression-free and overall survival in these patients. However, after a relatively short period of disease control, most patients develop resistance because of reactivation of the RAF-ERK (extracellular signal-regulated kinase) pathway, mediated in many cases by mutations in RAS. We found that BRAF inhibition induces invasion and metastasis in RAS mutant melanoma cells through a mechanism mediated by the reactivation of the MEK (mitogen-activated protein kinase kinase)-ERK pathway, increased expression and secretion of interleukin 8, and induction of protease-dependent invasion. These events were accompanied by a cell morphology switch from predominantly rounded to predominantly elongated cells. We also observed similar responses in BRAF inhibitor-resistant melanoma cells. These data show that BRAF inhibitors can induce melanoma cell invasion and metastasis in tumors that develop resistance to these drugs.

Topics: Animals; Blotting, Western; Cell Shape; Dimethyl Sulfoxide; Drug Resistance, Neoplasm; Enzyme-Linked Immunosorbent Assay; Humans; Indoles; Interleukin-8; MAP Kinase Signaling System; Melanoma; Mice; Mice, Nude; Neoplasm Invasiveness; Neoplasm Metastasis; Proto-Oncogene Proteins B-raf; Proto-Oncogene Proteins p21(ras); Skin Neoplasms; Statistics, Nonparametric; Sulfonamides

To evaluate the effects of treatment with the potent mutant BRAF inhibitors GSK2118436 or vemurafenib (PLX4720) on immune responses to metastatic melanoma in tissues taken before and after treatment.. Thirty-seven tumor biopsies were collected from 15 patients with unresectable American Joint Committee on Cancer stage III or IV melanoma immediately before and approximately 7 days after the commencement of BRAF inhibitor treatment and at the time of tumor progression. Immunohistochemical staining was carried out on the biopsies using specific antibodies for CD8, CD4, CD20, CD1a, and Granzyme B.. Tumor infiltration by CD4(+) and CD8(+) lymphocytes increased markedly following BRAF inhibitor treatment (both ρ = 0.015). There was a correlation between the degree of tumor infiltration by CD8(+) and Granzyme B-expressing lymphocytes in post-BRAF inhibitor-treated biopsies (r = 0.690 and ρ = 0.013). Increased intratumoral CD8(+) lymphocyte expression was correlated with a reduction in tumor size and an increase in necrosis in posttreatment biopsies (r = -0.793, ρ = 0.011; and r = 0.761, ρ = 0.004, respectively).. The increase in tumor-infiltrating lymphocytes induced by treatment with BRAF inhibitors provides strong support for conducting trials that combine BRAF inhibitors with immunotherapy in the hope of prolonging clinical responses.

Topics: Adult; Aged; Female; Granzymes; Humans; Imidazoles; Indoles; Lymphocytes, Tumor-Infiltrating; Male; Melanoma; Middle Aged; Mutation; Neoplasm Metastasis; Neoplasm Staging; Oximes; Prognosis; Protein Kinase Inhibitors; Proto-Oncogene Proteins B-raf; Sulfonamides; T-Lymphocytes; Young Adult