Characterization of DNA double‐strand break repair pathways in diffuse large B cell lymphoma

Abstract

Efficient DNA repair is indispensable for maintaining genomic integrity in humans. Cancer associated deletions and mutations are mainly due to misrepaired DNA double‐strand breaks (DSBs). Classical nonhomologous end joining (c‐NHEJ) and homologous recombination (HR) are two major DSB repair pathways in humans. An error prone, alternative NHEJ pathway that utilizes microhomology was also reported in cancer cells and to a lesser extent in normal cells. In the present study, we evaluated the efficiency of various DSB repair pathways in the most common lymphoma, the diffuse large B cell lymphoma (DLBCL). Here we show that DNA repair through c‐NHEJ pathway is limited in SUDHL8, a cell line derived from a DLBCL patient. Unlike c‐NHEJ, microhomology mediated end joining (MMEJ) was predominant at physiological temperature. Consistent with the observation, expression level of repair proteins such as LIGASE I, LIGASE III, PARP1, CtIP, and MRE11 was higher in DLBCL cells when compared to c‐NHEJ proteins. Further, inhibition of LIGASE I or MRE11, led to reduction in the efficiency of MMEJ in DLBCL cells. Besides, HR‐mediated DSB repair occurring through gene conversion was observed. Thus, our results reveal the predominance of MMEJ over c‐NHEJ in repairing DSBs in DLBCL cells, while error‐free repair through HR was also evident.

Involvement of classic and alternative non-homologous end joining pathways in hematologic malignancies: targeting strategies for treatment

“…In diffuse large B-cell lymphoma (DLBCL) cells, the expression of key MMEJ proteins, including Lig I, Lig III, PARP1, CtIP, and MRE11 elevates, while the level of C-NHEJ factors decreases [ 101 ]. SUDHL8, a cell line driven from a DLBCL patient, showed the increased expression of XRCC6 by four to five folds and the reduced expression of MRE11 by two folds, compared to benign reactive lymphocytes.…”

Impact of hypoxia on the double-strand break repair after photon and carbon ion irradiation of radioresistant HNSCC cells

“…NHEJ repairs DSBs throughout the cell cycle, whereas HR is only active during the S/G2 phases following DNA replication, which partly explains why the NHEJ-c pathway is involved in the repair of ~ 70% of DSBs in human cells, whereas HR is used in the residual ~ 30% 9 . The error-prone NHEJ-c pathway involves the heterodimer Ku70/80, which instantly recognizes the DSB ends with high affinity, inhibits the initiation of HR, and recruits proteins such as DNA-PK and Artemis.…”

TREX1 variants in Sjogren's syndrome related lymphomagenesis

“…In further studies, our aim is to explore whether TREX1 exonuclease activity is affected by the presence of the rs11797 TREX1 gene variant using commercially available 3'to 5' Exonuclease Activity Assays in isolated PBMCs from wild type and mutant carriers. Furthermore, given the implication of TREX1 in genomic instability [53] -a previously proposed mechanism for lymphomagenesis [54]-intrinsic DNA damage will be assessed using the comet assay in the same samples.…”