Involvement of homologous recombination in the synergism between cisplatin and poly (ADP‐ribose) polymerase inhibition

Abstract

Poly (ADP-ribose) polymerase (PARP) plays a critical role in responding to DNA damage, by activating DNA repair pathways responsible for cellular survival. Inhibition of PARP is used to treat certain solid cancers, such as breast and ovarian cancers. However, its effectiveness with other solid cancers, such as esophageal squamous cell carcinoma (ESCC), has not been clarified. We evaluated the effects of PARP inhibition on the survival of human esophageal cancer cells, with a special focus on the induction and repair of DNA double-strand breaks. The effects were monitored by colony formation assays and DNA damage responses, with immunofluorescence staining of cH2AX and RAD51. We found that PARP inhibition synergized with cisplatin, and the cells were highly sensitive, in a similar manner to the combination of cisplatin and 5-fluorouracil (5-FU). Comparable increases in RAD51 foci formation were observed after each combined treatment with cisplatin and either 3-aminobenzamide (3-AB) or 5-FU in three human esophageal cancer cell lines, TE11, TE14, and TE15. In addition, decreasing the amount of RAD51 by RNA interference rendered the TE11 cells even more hypersensitive to these treatments. Our findings suggested that the homologous recombinational repair pathway may be involved in the synergism between cisplatin and either 3-AB or 5-FU, and that 3-AB and 5-FU may similarly modify the cisplatin-induced DNA damage to types requiring the recruitment of RAD51 proteins for their repair. Understanding these mechanisms could be useful for improving the clinical outcome of ESCC patients who suffer from aggressive disease that presently lacks effective treatment options. (Cancer Sci 2013; 104: 1593-1599 G enomic integrity is maintained by the close cooperation of several DNA repair pathways. Any failure in these pathways can lead to unrepaired DNA lesions, which cause cell-cycle arrest and cell death, either directly or following DNA replication during the S phase of the cell cycle.(1,2) Therefore, the therapeutic effects of DNA-damaging agents may be enhanced by the inhibition of DNA repair. This feature makes DNA repair mechanisms a promising target for novel cancer treatment regimens.In recent years, poly (ADP-ribose) polymerase (PARP) inhibitors have emerged as a novel class of chemotherapeutic agents. An abundant nuclear protein that catalyzes the formation of PAR polymers from NAD + , PARP is attached primarily to glutamic acid residues on acceptor proteins.(3) It participates in maintaining genomic integrity, as it is a DNA damage-sensing protein that binds to DNA single-strand breaks (SSBs). (4,5) In addition, PARP plays a role in restarting stalled replication forks, by attracting Mre11 to these sites.(6,7) Therefore, the inhibition of PARP generates DNA damage, and the obstructed replication forks can be converted to replication-associated DNA double-strand breaks (DSBs), which lead to cell cycle arrest and cell death unless they are repaired by the homologous recombinational repair pathway (HR). (8,9) Recently, th...

Decreased Poly(ADP-Ribose) Polymerase 1 Expression Attenuates Glucose Oxidase-Induced Damage in Rat Cochlear Marginal Strial Cells

“…A wide array of pathological and physiological changes induced by aging, stress, ischemia, noise, and ototoxic agents can cause irreversible damage to marginal cells, leading to excessive generation of ROS and eventually to auditory impairment. PARP1, a molecular sensor of DNA damage [30], is activated when DNA is damaged and is thought to play a role in a variety of diseases, such as diabetes [6, 22], arthritis [23], Parkinson’s and Alzheimer’s diseases, cerebral ischemia, traumatic brain injury [24], and some malignancies such as ovarian carcinoma [25]. Regarding the inner ear, most studies about the effect of PARP1 have been conducted in the outer hair cells and a few have been carried out in spiral ganglion neurons.…”

“…Activated PARP1 has been implicated in several disease models [22–25]. However, the effect of PARP1 on marginal cells subjected to oxidative damage remains elusive.…”

Regulation of homologous recombinational repair by lamin B1 in radiation‐induced DNA damage

“…Clonogenicity was assessed as previously described (36). One thousand siRNA‐transfected cells were plated and maintained in 5 ml medium for 24 hours after X‐ray irradiation.…”

Let-7e sensitizes epithelial ovarian cancer to cisplatin through repressing DNA double strand break repair

“…HR is thought to be a conserved and error-free pathway to repair DSB compared with NHEJ, which is regarded as imprecise and potentially mutagenic [2, 3]. In addition, HR is related with cisplatin sensitivity in several solid tumors such as esophageal squamous carcinoma and embryonal carcinoma [4, 5]. The inhibition of HR repair capacity could effectively sensitize ovarian cancer cells to cisplatin [6].…”