Persistence of pre-leukemic clones during first remission and risk of relapse in acute myeloid leukemia.

Some patients with acute myeloid leukemia (AML) who are in complete remission after induction chemotherapy harbor persisting pre-leukemic clones, carrying a subset of leukemia-associated somatic mutations. There is conflicting evidence on the prognostic relevance of these clones for AML relapse. Here, we characterized paired pre-treatment and remission samples from 126 AML patients for mutations in 68 leukemia-associated genes. Fifty patients (40%) retained ⩾1 mutation during remission at a variant allele frequency of ⩾2%. Mutation persistence was most frequent in DNMT3A (65% of patients with mutations at diagnosis), SRSF2 (64%), TET2 (55%), and ASXL1 (46%), and significantly associated with older age (P<0.0001) and, in multivariate analyses adjusting for age, genetic risk, and allogeneic transplantation, with inferior relapse-free survival (hazard ratio, 2.34; P=0039) and overall survival (hazard ratio, 2.14; P=036). Patients with persisting mutations had a higher cumulative incidence of relapse before, but not after allogeneic stem cell transplantation. Our work underlines the relevance of mutation persistence during first remission as a novel risk factor in AML. Persistence of pre-leukemic clones may contribute to the inferior outcome of elderly AML patients. Allogeneic transplantation abrogated the increased relapse risk associated with persisting pre-leukemic clones, suggesting that mutation persistence may guide postremission treatment.Leukemia accepted article preview online, 18 December 2017. doi:10.1038/leu.2017.350.

Photocrosslinking demonstrates proximity of a 34 kDa membrane protein to different portions of preprolactin during translocation through the endoplasmic reticulum.

Photocrosslinking has been used to identify integral proteins of the endoplasmic reticulum membrane that are in proximity to nascent preprolactin during in vitro translocation. A photoreactive lysyl derivative was introduced into truncated preprolactin chains comprising 86 or 115 amino acids. Both with the 86mer, containing the reactive group in the signal sequence, and with the 115mer, containing the probe exclusively in the mature portion of the chain, photocrosslinking occurred to an approximately 35 kDa transmembrane glycoprotein, the signal sequence receptor (SSR). SSR is identical with a previously isolated abundant and ubiquitous 34 kDa membrane protein that appears to be essential for protein translocation.