APOBEC3 family proteins as drivers of virus evolution

The apolipoprotein B mRNA editing enzyme catalytic polypeptide-like (APOBEC) family consists of cytosine deaminases implicated in diverse and important biological functions. APOBEC3 (A3) proteins belong to the APOBEC/AID family, and they catalyze the deamination of cytosine to uracil in single-stranded DNA and, to a lesser extent, in RNA substrates. In humans, seven A3 genes have been identified (A3A, A3B, A3C, A3D, A3F, A3G, and A3H). The introduction of lethal G-to-A or C-to-U mutations into certain viral genomes leads to virus inactivation. However, the mutagenic capability of A3 proteins could serve as a source of mutations to drive virus evolution. Therefore, recent studies have implied the role of A3 proteins in aiding the evolution of viruses, conferring them with severe manifestations such as drug resistance and/or immune evasion. In this review, we discuss in depth the interactions of A3 proteins with viruses that infect humans and our self-proteins

Opossum APOBEC1 is a DNA mutator with retrovirus and retroelement restriction activity

APOBEC3s (A3s) are single-stranded DNA cytosine deaminases that provide innate immune defences against retroviruses and mobile elements. A3s are specific to eutherian mammals because no direct homologs exist at the syntenic genomic locus in metatherian (marsupial) or prototherian (monotreme) mammals. However, the A3s in these species have the likely evolutionary precursors, the antibody gene deaminase AID and the RNA/DNA editing enzyme APOBEC1 (A1). Here, we used cell culture-based assays to determine whether opossum A1 restricts the infectivity of retroviruses including human immunodeficiency virus type 1 (HIV-1) and the mobility of LTR/non-LTR retrotransposons. Opossum A1 partially inhibited HIV-1, as well as simian immunodeficiency virus (SIV), murine leukemia virus (MLV), and the retrotransposon MusD. The mechanism of inhibition required catalytic activity, except for human LINE1 (L1) restriction, which was deamination-independent. These results indicate that opossum A1 functions as an innate barrier to infection by retroviruses such as HIV-1, and controls LTR/non-LTR retrotransposition in marsupials

BRCAness Predicts Resistance to Taxane-Containing Regimens in Triple Negative Breast Cancer During Neoadjuvant Chemotherapy

AbstractBackgroundTo provide optimal treatment of heterogeneous triple negative breast cancer (TNBC), we need biomarkers that can predict the chemotherapy response.Patients and MethodsWe retrospectively investigated BRCAness in 73 patients with breast cancer who had been treated with taxane- and/or anthracycline-based neoadjuvant chemotherapy (NAC). Using multiplex, ligation-dependent probe amplification on formalin-fixed core needle biopsy (CNB) specimens before NAC and surgical specimens after NAC. BRCAness status was assessed with the assessor unaware of the clinical information.ResultsWe obtained 45 CNB and 60 surgical specimens from the 73 patients. Of the 45 CNB specimens, 17 had BRCAness (38.6% of all subtypes). Of the 23 TNBC CNB specimens, 14 had BRCAness (61% of TNBC cases). The clinical response rates were significantly lower for BRCAness than for non-BRCAness tumors, both for all tumors (58.8% vs. 89.3%, P = .03) and for TNBC (50% vs. 100%, P = .02). All tumors that progressed with taxane therapy had BRCAness. Of the patients with TNBC, those with non-BRCAness cancer had pathologic complete responses significantly more often than did those with BRCAness tumors (77.8% vs. 14.3%, P = .007). After NAC, the clinical response rates were significant lower for BRCAness than for non-BRCAness tumors in all subtypes (P = .002) and in TNBC cases (P = .008). After a median follow-up of 26.4 months, 6 patients—all with BRCAness—had developed recurrence. Patients with BRCAness had shorter progression-free survival than did those with non- BRCAness (P = .049).ConclusionIdentifying BRCAness can help predict the response to taxane, and changing regimens for BRCAness TNBC might improve patient survival. A larger prospective study is needed to further clarify this issue

BRCA1/2 Mutation Frequency is HIGH in Japanese Triple-Negative Breast Cancer Patients

Germline mutations of BRCA1/2 genes cause hereditary breast and/or ovarian cancer. However, whether guidelines like those of the National Comprehensive Cancer Network (NCCN) can suitably predict the likelihood of BRCA1/2 mutations in the Japanese population is unclear. Methods BRCA1/2 gene mutation frequencies were investigated in relation to parameters such as age, family history (FH), and breast cancer subtype using data collected from 922 Japanese breast cancer patients who underwent surgery between September 2010 and June 2013. BRCA1/2 mutations were present in 15 of 57 (26.3%) tested patients. The frequency of the mutations was not significantly related to age. Among the 180 patients who reported an FH of breast cancer, 11 of the 37 who were tested (29.7%) were positive for BRCA1/2 mutations. Of those with an FH of ovarian cancer (n = 34), seven of 12 patients tested (58.3%) were carriers of BRCA1/2 (P = 0.013). Six of these seven carriers were triple-negative breast cancer (TNBC) patients. In all, there were 97 TNBC patients, and the presence of the BRCA1/2 mutation in this subgroup was significantly greater than in non-TNBC patients, with 12 of 17 TNBC patients (70.5%) testing positive (P = 0.03). There were 59 TNBC patients < 60 years of age, and of the 16 (27.1%) who underwent BRCA1/2 genetic testing, 11 (68.8%) were found to have mutations in BRCA1/2. Among the TNBC patients, 29 also reported an FH of breast or ovarian cancer; of these, nine of the 13 tested (69.2%) were positive for a BRCA1/2 mutation. The data demonstrate that BRCA1/2 mutations are observed more frequently in TNBC patients, especially those < 60 years of age or in combination with an FH of breast and/or ovarian cancer, suggesting that some of the NCCN guidelines can adequately predict BRCA1/2 carriers in the Japanese population