This week in NEJM, researchers in the US and Canada examine recurrent somatic DICER1 mutations in non-epithelial ovarian cancer. The team sequenced the whole transcriptomes or exomes of non-epithelial ovarian tumors, and found closely clustered mutations in the region of DICER1 in 30 of the 102 samples. "These mutations were restricted to codons encoding metal-binding sites within the RNase IIIb catalytic centers, which are critical for microRNA interaction and cleavage, and were somatic in all 16 samples in which germline DNA was available for testing," the researchers write. "Somatic missense mutations affecting the RNase IIIb domain of DICER1 are common in non-epithelial ovarian tumors. These mutations do not obliterate DICER1 function but alter it in specific cell types, a novel mechanism through which perturbation of microRNA processing may be oncogenic."
Also in NEJM this week, researchers at the Mayo Clinic College of Medicine present a case study on the use of vemurafenib for the treatment of melanoma metastases to the brain. Vemurafenib, a BRAF V600E inhibitor, has recently received FDA approval for the treatment of metastatic melanoma in adults without brain metastases, the authors write. There are currently trials underway to assess the drug's efficacy in patients with brain metastases. In this case, the authors successfully used vemurafenib to treat a child with melanoma that had metastasized to the brain, for whom previous treatments had been unsuccessful. "One month after the initiation of treatment [with vemurafenib], the patient had a dramatic improvement in her symptoms, with MRI evidence of minimal increases in the size of the three larger hemorrhagic metastases and substantial decreases in edema and mass effect," the authors write. "A combination positron-emission tomographic–computed tomographic scan obtained three months later showed no systemic metastases and clear evidence of hypometabolism in the brain metastases. At last follow-up, all visualized sites of melanoma in the brain were substantially reduced."