BRAF Mutations and the Utility of RAF and MEK Inhibitors in Primary Brain Tumors

BRAF mutations have been identified as targetable, oncogenic mutations in many cancers. Given the paucity of treatments for primary brain tumors and the poor prognosis associated with high-grade gliomas, BRAF mutations in glioma are of considerable interest. In this review, we present the spectrum of BRAF mutations and fusion alterations present in each class of primary brain tumor based on publicly available databases and publications. We also summarize clinical experience with RAF and MEK inhibitors in patients with primary brain tumors and describe ongoing clinical trials of RAF inhibitors in glioma. Sensitivity to RAF and MEK inhibitors varies among BRAF mutations and between tumor types as only class I BRAF V600 mutations are sensitive to clinically available RAF inhibitors. While class II and III BRAF mutations are found in primary brain tumors, further research is necessary to determine their sensitivity to third-generation RAF inhibitors and/or MEK inhibitors. We recommend that the neuro-oncologist consider using these drugs primarily in the setting of a clinical trial for patients with BRAF-altered glioma in order to advance our knowledge of their efficacy in this patient population

Abstract 1415: The Notch ligand Jag 2 promotes growth and invasion in uveal melanoma cells

Abstract Uveal melanoma is the most common primary intraocular cancer in the adults, and up to 50% of patients die from hematogenous visceral metastases which are extremely resistant to chemotherapy. Using oligonucleotide expression array analysis of mRNA from primary uveal melanomas, we found that the Jag 2 ligand was 1.9 fold more expressed in tumors which metastasized than those which did not. Other Notch pathway members were also significantly induced in the metastatic cohort. We then used quantitative RT PCR to analyze mRNA extracted from a second cohort of 30 snap-frozen primary tumors, and confirmed that elevated Jag 2 mRNA levels were significantly associated (p = 0.048) with the metastatic Class 2 signature as compared to non-metastatic Class 1 uveal melanoma. To directly examine the importance of Jag 2 in driving cellular growth and invasion, we introduced the ligand into a uveal melanoma cell line, Mel 290, which has low baseline levels of Notch activity as measured by expression of the pathway targets Hes1, Hey1 and Hey2. The Jag 2-GFP-MSCV-infected cells showed a 2.5 to 6 fold induction of Notch targets Hey 1 and Hes1, indicating that pathway activity had been induced. While overall growth of the Jag 2-GFP-MSCV infected cultures as measured by MTT increased only slightly, overexpression of Jag 2 induced an approximately 3 fold increase in clonogenic growth in soft agar. Finally, we assayed the migratory properties of the cells using a wound-healing (“scratch”) assay, as well as their ability to invade Matrigel. Jag 2 expressing cells showed increased motility in both of these tests, with a significant (p = 0.0003) approximately 2 fold induction of transwell invasion capacity. Our data suggest that expression of the Notch ligand Jag 2 may play an important role in uveal melanoma growth and metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1415. doi:10.1158/1538-7445.AM2011-1415</jats:p

Notch Signaling Promotes Growth and Invasion in Uveal Melanoma

PURPOSE: To determine whether uveal melanoma, the most common primary intraocular malignancy in adults, requires Notch activity for growth and metastasis. EXPERIMENTAL DESIGN: Expression of Notch pathway members was characterized in primary tumor samples and in cell lines, along with the effects of Notch inhibition or activation on tumor growth and invasion. RESULTS: Notch receptors, ligands, and targets were expressed in all five cell lines examined and in 30 primary uveal melanoma samples. Interestingly, the three lines with high levels of baseline pathway activity (OCM1, OCM3, and OCM8) had their growth reduced by pharmacologic Notch blockade using the γ-secretase inhibitor (GSI) MRK003. In contrast, two uveal melanoma lines (Mel285 and Mel290) with very low expression of Notch targets were insensitive to the GSI. Constitutively active forms of Notch1 and Notch2 promoted growth of uveal melanoma cultures and were able to rescue the inhibitory effects of GSI. MRK003 treatment also inhibited anchorage-independent clonogenic growth and cell invasion and reduced phosphorylation levels of STAT3 and extracellular signal-regulated kinase (Erk)1/2. Suppression of canonical Notch activity using short hairpin RNA targeting Notch2 or CBF1 was also able to reduce tumor growth and invasion. Finally, intraocular xenograft growth was significantly decreased by GSI treatment. CONCLUSION: Our findings suggest that Notch plays an important role in inducing proliferation and invasion in uveal melanoma and that inhibiting this pathway may be effective in preventing tumor growth and metastasis

Feasibility and Biological Activity of a Ketogenic/Intermittent-Fasting Diet in Patients With Glioma

OBJECTIVE: To examine the feasibility, safety, systemic biological activity, and cerebral activity of a ketogenic dietary intervention in patients with glioma.METHODS: 25 patients with biopsy-confirmed WHO Grade 2-4 astrocytoma with stable disease following adjuvant chemotherapy were enrolled in an 8-week GLioma Atkins-based Diet (GLAD). GLAD consisted of 2 fasting days (calorie