Serum Alpha-fetoprotein Levels and Clinical Outcomes in the Phase III CELESTIAL Study of Cabozantinib versus Placebo in Patients with Advanced Hepatocellular Carcinoma

PURPOSE: The phase III CELESTIAL study demonstrated improved overall survival (OS) and progression-free survival (PFS) with cabozantinib versus placebo in patients with previously treated, advanced hepatocellular carcinoma (HCC). We analyzed outcomes by baseline alpha-fetoprotein (AFP) and on-treatment AFP changes. PATIENTS AND METHODS: Serum AFP was measured every 8 weeks by blinded, centralized testing. Outcomes were analyzed by baseline AFP bifurcated at 400 ng/mL and by on-treatment AFP response (≥20% decrease from baseline at Week 8). The optimal cutoff for change in AFP at Week 8 was evaluated using maximally selected rank statistics. RESULTS: Median OS for cabozantinib versus placebo was 13.9 versus 10.3 months [HR, 0.81; 95% confidence interval (CI), 0.62-1.04] for patients with baseline AFP <400 ng/mL, and 8.5 versus 5.2 months (HR, 0.71; 95% CI, 0.54-0.94) for patients with baseline AFP ≥400 ng/mL. Week 8 AFP response rate was 50% for cabozantinib versus 13% for placebo. In the cabozantinib arm, median OS for patients with and without AFP response was 16.1 versus 9.1 months (HR, 0.61; 95% CI, 0.45-0.84). AFP response was independently associated with longer OS. The optimal cutoff for association with OS in the cabozantinib arm was ≤0% change in AFP at Week 8 [AFP control; HR 0.50 (95% CI, 0.35-0.71)]. HRs for PFS were consistent with those for OS. CONCLUSIONS: Cabozantinib improved outcomes versus placebo across a range of baseline AFP levels. On-treatment AFP response and control rates were higher with cabozantinib than placebo, and were associated with longer OS and PFS with cabozantinib

Activating mutations of the GNAQ gene: a frequent event in primary melanocytic neoplasms of the central nervous system

Primary melanocytic neoplasms of the central nervous system (CNS) are uncommon neoplasms derived from melanocytes that normally can be found in the leptomeninges. They cover a spectrum of malignancy grades ranging from low-grade melanocytomas to lesions of intermediate malignancy and overtly malignant melanomas. Characteristic genetic alterations in this group of neoplasms have not yet been identified. Using direct sequencing, we investigated 19 primary melanocytic lesions of the CNS (12 melanocytomas, 3 intermediate-grade melanocytomas, and 4 melanomas) for hotspot oncogenic mutations commonly found in melanocytic tumors of the skin (BRAF, NRAS, and HRAS genes) and uvea (GNAQ gene). Somatic mutations in the GNAQ gene at codon 209, resulting in constitutive activation of GNAQ, were detected in 7/19 (37%) tumors, including 6/12 melanocytomas, 0/3 intermediate-grade melanocytomas, and 1/4 melanomas. These GNAQ-mutated tumors were predominantly located around the spinal cord (6/7). One melanoma carried a BRAF point mutation that is frequently found in cutaneous melanomas (c.1799 T>A, p.V600E), raising the question whether this is a metastatic rather than a primary tumor. No HRAS or NRAS mutations were detected. We conclude that somatic mutations in the GNAQ gene at codon 209 are a frequent event in primary melanocytic neoplasms of the CNS. This finding provides new insight in the pathogenesis of these lesions and suggests that GNAQ-dependent mitogen-activated kinase signaling is a promising therapeutic target in these tumors. The prognostic and predictive value of GNAQ mutations in primary melanocytic lesions of the CNS needs to be determined in future studies

Crystal structure of the GTPase-activating domain of human p120GAP and implications for the interaction with Ras

Ras-related GTP-binding proteins function as molecular switches which cycle between GTP-bound 'on'- and GDP-bound 'off'-states. GTP hydrolysis is the common timing mechanism that mediates the return from the 'on' to the 'off'-state. It is usually slow but can be accelerated by orders of magnitude upon interaction with GTPase-activating proteins (GAPs). In the case of Ras, a major regulator of cellular growth, point mutations are found in approximately 30% of human tumours which render the protein unable to hydrolyse GTP, even in the presence of Ras-GAPs. The first structure determination of a GTPase-activating protein reveals the catalytically active fragment of the Ras-specific p120GAP (ref. 2), GAP-334, as an elongated, exclusively helical protein which appears to represent a novel protein fold. The molecule consists of two domains, one of which contains all the residues conserved among different GAPs for Ras. From the location of conserved residues around a shallow groove in the central domain we can identify the site of interaction with Ras x GTP. This leads to a model for the interaction between Ras and GAP that satisfies numerous biochemical and genetic data on this important regulatory proces

Frequent somatic mutations of GNAQ in uveal melanoma and blue naevi

BRAF and NRAS are common targets for somatic mutations in benign and malignant neoplasms that arise from melanocytes situated in epithelial structures, and lead to constitutive activation of the mitogen-activated protein (MAP) kinase pathway. However, BRAF and NRAS mutations are absent in a number of other melanocytic neoplasms in which the equivalent oncogenic events are currently unknown. Here we report frequent somatic mutations in the heterotrimeric G protein alpha-subunit, GNAQ, in blue naevi (83%) and ocular melanoma of the uvea (46%). The mutations occur exclusively in codon 209 in the Ras-like domain and result in constitutive activation, turning GNAQ into a dominant acting oncogene. Our results demonstrate an alternative route to MAP kinase activation in melanocytic neoplasia, providing new opportunities for therapeutic intervention

Combined PKC and MEK inhibition in uveal melanoma with GNAQ and GNA11 mutations

Uveal melanoma (UM) is a genetically and biologically distinct type of melanoma, and once metastatic there is no effective treatment currently available. 80% of UMs harbor mutations in the Gα(q) family members GNAQ and GNA11. Understanding the effector pathways downstream of these oncoproteins is important to identify opportunities for targeted therapy. We report consistent activation of the protein kinase C (PKC) and MAPK pathways as a consequence of GNAQ or GNA11 mutation. PKC inhibition with AEB071 or AHT956 suppressed PKC and MAPK signalling and induced G1 arrest selectively in melanoma cell lines carrying GNAQ or GNA11 mutations. In contrast, treatment with two different MEK inhibitors, PD0325901 and MEK162, inhibited the proliferation of melanoma cell lines irrespective of their mutation status, indicating that in the context of GNAQ or GNA11 mutation, MAPK activation can be attributed to activated PKC. AEB071 significantly slowed the growth of tumors in an allograft model of GNAQ(Q209L) transduced melanocytes, but did not induce tumor shrinkage. In vivo and in vitro studies showed that PKC inhibitors alone were unable to induce sustained suppression of MAP-kinase signaling. However, combinations of PKC and MEK inhibition, using either PD0325901 or MEK162, led to sustained MAP-kinase pathway inhibition and showed a strong synergistic effect in halting proliferation and in inducing apoptosis in vitro. Furthermore, combining PKC and MEK inhibition was efficacious in vivo, causing marked tumor regression in a uveal melanoma xenograft model. Our data identifies PKC as a rational therapeutic target for melanoma patients with GNAQ or GNA11 mutations, and demonstrates combined MEK and PKC inhibition is synergistic, with superior efficacy compared to treatment with either approach alone