Giuseppe Palmieri

Mutations of the BRAF gene in human cancer

Cancers arise owing to the accumulation of mutations in critical genes that alter normal programmes of cell proliferation, differentiation and death. As the first stage of a systematic genome-wide screen for these genes, we have prioritized for analysis signalling pathways in which at least one gene is mutated in human cancer. The RAS–RAF–MEK–ERK–MAP kinase pathway mediates cellular responses to growth signals. RAS is mutated to an oncogenic form in about 15% of human cancer. The three RAF genes code for cytoplasmic serine/threonine kinases that are regulated by binding RAS. Here we report BRAF somatic missense mutations in 66% of malignant melanomas and at lower frequency in a wide range of human cancers. All mutations are within the kinase domain, with a single substitution (V599E) accounting for 80%. Mutated BRAF proteins have elevated kinase activity and are transforming in NIH3T3 cells. Furthermore, RAS function is not required for the growth of cancer cell lines with the V599E mutation. As BRAF is a serine/threonine kinase that is commonly activated by somatic point mutation in human cancer, it may provide new therapeutic opportunities in malignant melanoma.

BRAF/NRAS Mutation Frequencies Among Primary Tumors and Metastases in Patients With Melanoma

PURPOSE The prevalence of BRAF, NRAS, and p16CDKN2A mutations during melanoma progression remains inconclusive. We investigated the prevalence and distribution of mutations in these genes in different melanoma tissues. PATIENTS AND METHODS In all, 291 tumor tissues from 132 patients with melanoma were screened. Paired samples of primary melanomas (n = 102) and synchronous or asynchronous metastases from the same patients (n = 165) were included. Tissue samples underwent mutation analysis (automated DNA sequencing). Secondary lesions included lymph nodes (n = 84), and skin (n = 36), visceral (n = 25), and brain (n = 44) sites. RESULTS BRAF/NRAS mutations were identified in 58% of primary melanomas (43% BRAF; 15% NRAS); 62% in lymph nodes, 61% subcutaneous, 56% visceral, and 70% in brain sites. Mutations were observed in 63% of metastases (48% BRAF; 15% NRAS), a nonsignificant increase in mutation frequency after progression from primary melanoma. Of the paired samples, lymph nodes (93% consistency) and visceral metastases (96% consistency) presented a highly similar distribution of BRAF/NRAS mutations versus primary melanomas, with a significantly less consistent pattern in brain (80%) and skin metastases (75%). This suggests that independent subclones are generated in some patients. p16CDKN2A mutations were identified in 7% and 14% of primary melanomas and metastases, with a low consistency (31%) between secondary and primary tumor samples. CONCLUSION In the era of targeted therapies, assessment of the spectrum and distribution of alterations in molecular targets among patients with melanoma is needed. Our findings about the prevalence of BRAF/NRAS/p16CDKN2A mutations in paired tumor lesions from patients with melanoma may be useful in the management of this disease.

The role of BRAF V600 mutation in melanoma.

BRAF is a serine/threonine protein kinase activating the MAP kinase/ERK-signaling pathway. About 50 % of melanomas harbors activating BRAF mutations (over 90 % V600E). BRAFV600E has been implicated in different mechanisms underlying melanomagenesis, most of which due to the deregulated activation of the downstream MEK/ERK effectors. The first selective inhibitor of mutant BRAF, vemurafenib, after highly encouraging results of the phase I and II trial, was compared to dacarbazine in a phase III trial in treatment-naïve patients (BRIM-3). The study results showed a relative reduction of 63 % in risk of death and 74 % in risk of tumor progression. Considering all trials so far completed, median overall survival reached approximately 16 months for vemurafenib compared to less than 10 months for dacarbazine treatment. Vemurafenib has been extensively tested on melanoma patients expressing the BRAFV600E mutated form; it has been demonstrated to be also effective in inhibiting melanomas carrying the V600K mutation. In 2011, both FDA and EMA therefore approved vemurafenib for metastatic melanoma carrying BRAFV600 mutations. Some findings suggest that continuation of vemurafenib treatment is potentially beneficial after local therapy in a subset of patients with disease progression (PD). Among who continued vemurafenib >30 days after local therapy of PD lesion(s), a median overall survival was not reached, with a median follow-up of 15.5 months from initiation of BRAF inhibitor therapy. For patients who did not continue treatment, median overall survival from the time of disease progression was 1.4 months. A clinical phase I/II trial is evaluating the safety, tolerability and efficacy of vemurafenib in combination with the CTLA-4 inhibitor mAb ipilimumab. In the BRIM-7 trial vemurafenib is tested in association with GDC-0973, a potent and highly selective inhibitor of MEK1/2. Preliminary data seem to indicate that an additional inhibitor of mutated BRAF, GSK2118436, might be also active on a wider range of BRAF mutations (V600E-K-D-R); actually, treatment with such a compound is under evaluation in a phase III study among stage III-IV melanoma patients positive for BRAF mutations. Overall, BRAF inhibitors were well tolerated; common adverse events are arthralgia, rash, fatigue, alopecia, keratoacanthoma or cutaneous squamous-cell carcinoma, photosensitivity, nausea, and diarrhea, with some variants between different inhibitors.

Abscopal effects of radiotherapy on advanced melanoma patients who progressed after ipilimumab immunotherapy.

Cancer radiotherapy (RT) may induce what is referred to as the “abscopal effect,” a regression of non-irradiated metastatic lesions distant from the primary tumor site directly subject to irradiation. This clinical response is rare, but has been surmised to be an immune-mediated phenomenon, suggesting that immunotherapy and RT could potentially synergize. Here, we report the outcome of patients with advanced melanoma treated with the immune checkpoint blockade monoclonal antibody antagonist, ipilimumab followed by RT. Patients were selected for enrollment at the National Cancer Institute “Fondazione G.Pascale” through the expanded access program in Italy. Those who experienced disease progression after ipilimumab thus received subsequent RT and were selected for analysis. Among 21 patients, 13 patients (62%) received RT to treat metastases in the brain and 8 received RT directed at extracranial sites. An abscopal response was observed in 11 patients (52%), 9 of whom had partial responses (43%) and 2 had stable disease (10%). The median time from RT to an abscopal response was 1 month (range 1–4). Median overall survival (OS) for all 21 patients was 13 months (range 6–26). Median OS for patients with abscopal responses was extended to 22.4 months (range 2.5–50.3) vs. 8.3 months (range 7.6–9.0) without. A local response to RT was detected in 13 patients (62%) and, of these, 11 patients (85%) had an abscopal response and abscopal effects were only observed among patients exhibiting a local response. These results suggest RT after ipilimumab may lead to abscopal responses in some patients with advanced melanoma correlating with prolonged OS. Our data also suggest that local responses to RT may be predictive of abscopal responses. Further research in larger randomized trials is needed to validate these results.

Main roads to melanoma

The characterization of the molecular mechanisms involved in development and progression of melanoma could be helpful to identify the molecular profiles underlying aggressiveness, clinical behavior, and response to therapy as well as to better classify the subsets of melanoma patients with different prognosis and/or clinical outcome. Actually, some aspects regarding the main molecular changes responsible for the onset as well as the progression of melanoma toward a more aggressive phenotype have been described. Genes and molecules which control either cell proliferation, apoptosis, or cell senescence have been implicated. Here we provided an overview of the main molecular changes underlying the pathogenesis of melanoma. All evidence clearly indicates the existence of a complex molecular machinery that provides checks and balances in normal melanocytes. Progression from normal melanocytes to malignant metastatic cells in melanoma patients is the result of a combination of down- or up-regulation of various effectors acting on different molecular pathways.

X-inactivation patch size in human female tissue confounds the assessment of tumor clonality

Most models of tumorigenesis assume that tumors are monoclonal in origin. This conclusion is based largely on studies using X chromosome-linked markers in females. One important factor, often ignored in such studies, is the distribution of X-inactivated cells in tissues. Because lyonization occurs early in development, many of the progeny of a single embryonic stem cell are grouped together in the adult, forming patches. As polyclonality can be demonstrated only at the borders of X-inactivation patches, the patch size is crucial in determining the chance of demonstrating polyclonality and hence the number of tumors that need to be examined to exclude polyclonality. Previously studies using X-linked genes such as glucose-6-phosphate dehydrogenase have been handicapped by the need to destroy the tissues to study the haplotypes of glucose-6-phosphate dehydrogenase [Fialkow, P.-J. (1976) Biochim. Biophys. Acta 458, 283–321] or to determine the restriction fragment length polymorphisms of X chromosome-linked genes [Vogelstein, B., Fearon, E. R., Hamilton, S. R. & Feinberg, A. P. (1985) Science 227, 642–645]. Here we visualize X-inactivation patches in human females directly. Results show that the patch size is relatively large in both the human colon and breast, confounding assessment of tumor clonality with traditional X-inactivation studies.

HCV-related hepatocellular carcinoma: From chronic inflammation to cancer.

Hepatitis C virus (HCV) infection is a worldwide health problem because of its incidence and pathogenicity. It might evolve into chronic disease, cirrhosis, and/or hepatocellular carcinoma (HCC) and the outcome is mainly determined by the host immune response. For viral clearance, combined innate and adaptive immune responses are required; resolution requires a vigorous, durable, polyclonal CD4(+) and CD8(+) T-cell response, with an increase in virus-specific CD8(+) T cells or cytotoxic T lymphocytes. Failure of efficient immune response can lead to chronic inflammation, tissue remodeling through cell growth, apoptosis and/or necrosis and induction of oxidative stress. Development of fibrosis and/or cirrhosis plus a microenvironment conducive to genomic instability mutations will promote neoplastic transformation. System governance derives from cellular (regulatory cells) and humoral (cytokines and chemokines) immune networks. Therefore, HCC pathogenesis may be a model to study the disease progression from chronic inflammation to cancer allowing design of new strategies targeting the immune response, thereby modifying disease outcome.

Polymerase Chain Reaction-Based Detection of Circulating Melanoma Cells as an Effective Marker of Tumor Progression

PURPOSE Reverse transcriptase (RT) polymerase chain reaction (PCR) with multiple markers has been demonstrated to be highly sensitive in detecting circulating cells from patients with malignant melanoma (MM). We evaluated the clinical significance of the presence in peripheral blood of specific PCR-positive mRNA markers as an expression of circulating melanoma cells. PATIENTS AND METHODS Total cellular RNA was obtained from the peripheral blood of 235 patients with either localized (n = 154) or metastatic (n = 81) melanoma. We performed RT-PCR using tyrosinase, p97, MUC18, and MelanA/MART1 as gene markers. The PCR products were analyzed by gel electrophoresis and Southern blot hybridization. In addition, 20 healthy subjects and 21 patients with nonmelanoma cancer were used as negative controls. RESULTS Although detected at various levels among assessable patients, each mRNA marker was significantly correlated with disease stage. A significant correlation with disease stage was demonstrated for patients who were positive to all four markers (P < .0001) or to at least three markers (P < .001). Univariate analysis showed a significant correlation between risk of recurrence (evaluated in stage I, II, and III patients) and increasing number of PCR-positive markers (P = .0002). Logistic regression multivariate analysis indicated that each single marker (except tyrosinase) and, more especially, the presence of four PCR-positive markers remained statistically independent prognostic factors for tumor progression. CONCLUSION Our data establish the existence of a significant correlation among clinical stages, tumor progression, and presence of circulating melanoma-associated antigens in peripheral blood of MM patients. Preliminary assessment of a subset of patients with a higher risk of recurrence needs longer follow-up and further studies to define the role of RT-PCR in monitoring MM patients.

Prune cAMP phosphodiesterase binds nm23-H1 and promotes cancer metastasis.

We identify a new enzymatic activity underlying metastasis in breast cancer and describe its susceptibility to therapeutic inhibition. We show that human prune (h-prune), a phosphoesterase DHH family appertaining protein, has a hitherto unrecognized cyclic nucleotide phosphodiesterase activity effectively suppressed by dipyridamole, a phosphodiesterase inhibitor. h-prune physically interacts with nm23-H1, a metastasis suppressor gene. The h-prune PDE activity, suppressed by dipyridamole and enhanced by the interaction with nm23-H1, stimulates cellular motility and metastasis processes. Out of 59 metastatic breast cancer cases analyzed, 22 (37%) were found to overexpress h-prune, evidence that this novel enzymatic activity is involved in promoting cancer metastasis.

NF-κB as potential target in the treatment of melanoma

The RAS/MAP kinase pathway has attracted attention because activating mutations of the BRAF serine/threonine kinase was described in over 50% of melanomas. Very recently, selective and potent BRAF inhibitors have been developed. Several other signal transduction pathways have been found to be constitutively active or mutated in other subsets of melanoma tumors that are potentially targetable with new agents. Among these, NFκB is another pathway that melanoma tumors use to achieve survival, proliferation and resistance to apoptosis. Inhibition of NF-κB activation appears to be a very promising option for anti-cancer therapies.