Contradictory mRNA and protein misexpression of EEF1A1 in ductal breast carcinoma due to cell cycle regulation and cellular stress

Encoded by EEF1A1, the eukaryotic translation elongation factor eEF1α1 strongly promotes the heat shock response, which protects cancer cells from proteotoxic stress, following for instance oxidative stress, hypoxia or aneuploidy. Unexpectedly, therefore, we find that EEF1A1 mRNA levels are reduced in virtually all breast cancers, in particular in ductal carcinomas. Univariate and multivariate analyses indicate that EEF1A1 mRNA underexpression independently predicts poor patient prognosis for estrogen receptor-positive (ER+) cancers. EEF1A1 mRNA levels are lowest in the most invasive, lymph node-positive, advanced stage and postmenopausal tumors. In sharp contrast, immunohistochemistry on 100 ductal breast carcinomas revealed that at the protein level eEF1α1 is ubiquitously overexpressed, especially in ER+ , progesterone receptor-positive and lymph node-negative tumors. Explaining this paradox, we find that EEF1A1 mRNA levels in breast carcinomas are low due to EEF1A1 allelic copy number loss, found in 27% of tumors, and cell cycle-specific expression, because mRNA levels are high in G1 and low in proliferating cells. This also links estrogen-induced cell proliferation to clinical observations. In contrast, high eEF1α1 protein levels protect tumor cells from stress-induced cell death. These observations suggest that, by obviating EEF1A1 transcription, cancer cells can rapidly induce the heat shock response following proteotoxic stress, and survive

Targeting DNA Damage Response and Replication Stress in Pancreatic Cancer

Background and aims: Continuing recalcitrance to therapy cements pancreatic cancer (PC) as the most lethal malignancy, which is set to become the second leading cause of cancer death in our society. The study aim was to investigate the association between DNA damage response (DDR), replication stress and novel therapeutic response in PC to develop a biomarker driven therapeutic strategy targeting DDR and replication stress in PC. Methods: We interrogated the transcriptome, genome, proteome and functional characteristics of 61 novel PC patient-derived cell lines to define novel therapeutic strategies targeting DDR and replication stress. Validation was done in patient derived xenografts and human PC organoids. Results: Patient-derived cell lines faithfully recapitulate the epithelial component of pancreatic tumors including previously described molecular subtypes. Biomarkers of DDR deficiency, including a novel signature of homologous recombination deficiency, co-segregates with response to platinum (P < 0.001) and PARP inhibitor therapy (P < 0.001) in vitro and in vivo. We generated a novel signature of replication stress with which predicts response to ATR (P < 0.018) and WEE1 inhibitor (P < 0.029) treatment in both cell lines and human PC organoids. Replication stress was enriched in the squamous subtype of PC (P < 0.001) but not associated with DDR deficiency. Conclusions: Replication stress and DDR deficiency are independent of each other, creating opportunities for therapy in DDR proficient PC, and post-platinum therapy

Additional file 1: of In epithelial cancers, aberrant COL17A1 promoter methylation predicts its misexpression and increased invasion

Supplementary Material containing Table S1 (Prognostic strength of misexpression of collagen genes in breast cancer), Table S2 (Clinicopathological features of the breast cancer patients analyzed by immunohistochemistry), Table S3 (Clinicopathological features of the cervical cancer patients analyzed by immunohistochemistry), Figure S1 (H&E stained sections of corresponding samples shown in Fig. 2), Figure S2 (Schematic of the promoter and 5’ end of the COL17A1 gene), and Supplementary References. (PDF 1136 kb

RAD51-associated protein 1 (RAD51AP1) interacts with the meiotic recombinase DMC1 through a conserved motif

Free to read on publisher website Homologous recombination (HR) reactions mediated by the RAD51 recombinase are essential for DNA and replication fork repair, genome stability, and tumor suppression. RAD51-associated protein 1 (RAD51AP1) is an important HR factor that associates with and stimulates the recombinase activity of RAD51. We have recently shown that RAD51AP1 also partners with the meiotic recombinase DMC1, displaying isoform-specific interactions with DMC1. Here, we have characterized the DMC1 interaction site in RAD51AP1 by a series of truncations and point mutations to uncover a highly conserved WVPP motif critical for DMC1 interaction but dispensable for RAD51 association. This RAD51AP1 motif is reminiscent of the FVPP motif in the tumor suppressor protein BRCA2 that mediates DMC1 interaction. These results further implicate RAD51AP1 in meiotic HR via RAD51 and DMC1

NR4A2 promotes DNA double-strand break repair upon exposure to UVR

Exposure of melanocytes to ultraviolet radiation (UVR) induces the formation of UV-lesions that can produce deleterious effects in genomic DNA. Encounters of replication forks with unrepaired UV-lesions can lead to several complex phenomena, such as the formation of DNA double strand breaks (DSBs). The NR4A family of nuclear receptors are transcription factors that have been associated with mediating DNA repair functions downstream of the MC1R signalling pathway in melanocytes. In particular, emerging evidence shows that upon DNA damage, the NR4A2 receptor can translocate to sites of UV-lesion by mechanisms requiring post-translational modifications within the N-terminal domain and at a serine residue in the DNA biding domain at position 337. Following this, NR4A2 aids in DNA repair by facilitating chromatin relaxation, allowing accessibility for DNA repair machinery. Using A2058 and HT144 melanoma cells engineered to stably express wild-type or mutant forms of the NR4A2 proteins, we reveal that the expression of functional NR4A2 is associated with elevated cytoprotection against UVR. Conversely, knock-down of NR4A2 expression by siRNA results in a significant loss of cell viability after UV insult. By analysing the kinetics of the ensuing 53BP1 and RAD51 foci following UV-irradiation, we also reveal that the expression of mutant NR4A2 isoforms, lacking the ability to translocate, trans-activate or undergo phosphorylation, display compromised repair capacity. Implications: These data expand the understanding of the mechanism by which the NR4A2 nuclear receptor can facilitate DNA DSB repair

Translocation breakpoints preferentially occur in euchromatin and acrocentric chromosomes

Chromosomal translocations drive the development of many hematological and some solid cancers. Several factors have been identified to explain the non-random occurrence of translocation breakpoints in the genome. These include chromatin density, gene density and CCCTC-binding factor (CTCF)/cohesin binding site density. However, such factors are at least partially interdependent. Using 13,844 and 1563 karyotypes from human blood and solid cancers, respectively, our multiple regression analysis only identified chromatin density as the primary statistically significant predictor. Specifically, translocation breakpoints preferentially occur in open chromatin. Also, blood and solid tumors show markedly distinct translocation signatures. Strikingly, translocation breakpoints occur significantly more frequently in acrocentric chromosomes than in non-acrocentric chromosomes. Thus, translocations are probably often generated around nucleoli in the inner nucleoplasm, away from the nuclear envelope. Importantly, our findings remain true both in multivariate analyses and after removal of highly recurrent translocations. Finally, we applied pairwise probabilistic co-occurrence modeling. In addition to well-known highly prevalent translocations, such as those resulting in BCR-ABL1 (BCR-ABL) and RUNX1-RUNX1T1 (AML1-ETO) fusion genes, we identified significantly underrepresented translocations with putative fusion genes, which are probably subject to strong negative selection during tumor evolution. Taken together, our findings provide novel insights into the generation and selection of translocations during cancer development