N-ras mutations in human cutaneous melanoma from sun-exposed body sites.

Abstract

In 7 of 37 patients with cutaneous melanoma, mutations in the N-ras gene were found. The primary tumors of these seven patients were exclusively localized on body sites continuously exposed to sunlight. Moreover, the ras mutations were all at or near dipyrimidine sites known to be targets of UV damage. Two primary tumors were biclonal with respect to ras mutation. An active role for UV irradiation in induction of the mutations is suggested.In animals, a wide range of xenobiotic agents are capable of inducing mutations in the r-as oncogene family (2). Little is known, however, about the involvement of mutagenic agents in the induction of ras mutations in humans. For human cutaneous melanoma, there is epidemiological evidence suggesting a role of UV irradiation in occurrence of the tumor (18).N-ras activated in melanoma. To investigate the role of UV irradiation in the activation of ras genes, we studied 63 tumor samples from 37 cutaneous melanoma patients (Table 1) for mutations in H-, K-, or N-r-as. These samples included 10 primary tumors, 40 metastases, and 13 cell lines, all of the non-lentigo maligna type. To analyze mutational activation of ras genes, polymerase chain reaction-amplified DNA samples were prepared aR described previously (17) either from DNA obtained from fresh tumor specimens and cell lines or from Formalin-fixed and paraffin-embedded material (16). All samples contained at least 50% tumor cells. In certain cases (e.g., primary tumors of patients 4 and 10), parts of paraffin sections that contained more than 90% tumor cells were chosen. The amplified DNA was spotted onto nylon membranes and hybridized to probes 20 nucleotides long as described elsewhere (21) (Fig.

Immunohistochemistry is highly sensitive and specific for the detection of NRASQ61R mutation in melanoma

“…The frequency of NRAS mutation in melanoma is 15-20% but if only melanomas confined to continuously sun-exposed sites are considered, the frequency rises up significantly. 29 In conclusion, the N-Ras (Q61R) antibody is highly sensitive and specific for the detection of mutant NRASQ61R melanoma in formalin-fixed and paraffin-embedded samples. This immunohistochemical method has several advantages: it is cost effective, uses minimal tissue, and provides a result at the time of pathologic diagnosis.…”

Combined targeting of MEK and PI3K/mTOR effector pathways is necessary to effectively inhibit NRAS mutant melanoma in vitro and in vivo

“…In our hands, the observed effect with the combination treatment was antagonistic in all cell lines at a ratio of MEKi:CDKi 4,6 = 1:16. When different ratios were used in cell line MM415, no significant difference was noted between the MEKi alone and the combination of MEKi+CDKi 4,6 (Fig. S9).…”

“…However, these results need to be interpreted with caution as other ratios and concentrations could still be synergistic. We also did not test MEKi+CDKi 4,6 in vivo.…”

“…O ncogenic mutations in codons 12, 13, or 61 of the rat sarcoma (RAS) family of small GTPases, Kirsten rat sarcoma viral oncogene homolog (KRAS), Harvey rat sarcoma viral oncogene homolog (HRAS), and neuroblastoma RAS viral oncogene homolog (NRAS) occur in approximately one-third of all human cancers with NRAS mutations found in about 15-20% of melanomas (1)(2)(3)(4)(5)(6)(7). Mutated RAS proteins activate signaling pathways that promote the cell division cycle and cell growth and suppress apoptosis.…”

Genes involved in cell cycle G1 checkpoint control are frequently mutated in human melanoma metastases

“…Recently published data point to an effect of activated H-ras p21 leading to overexpression of cyclin Dl (Filmus et al, 1994). Altered N-ras genes, predominantly with mutations in codon 61 and/or altered N-ras gene expression levels have been registered in human melanomas (Albino et al, 1989;Van't Veer et al, 1989;Ball et al, 1994;Platz et al, 1994Platz et al, , 1995b.…”