Genomic evolution in Barrett's adenocarcinoma cells: critical roles of elevated hsRAD51, homologous recombination and Alu sequences in the genome

Abstract

A prominent feature of most cancers including Barrett’s adenocarcinoma (BAC) is genetic instability, which is associated with development and progression of disease. In this study, we investigated the role of recombinase (hsRAD51), a key component of homologous recombination (HR)/repair, in evolving genomic changes and growth of BAC cells. We show that the expression of RAD51 is elevated in BAC cell lines and tissue specimens, relative to normal cells. HR activity is also elevated and significantly correlates with RAD51 expression in BAC cells. The suppression of RAD51 expression, by short hairpin RNA (shRNA) specifically targeting this gene, significantly prevented BAC cells from acquiring genomic changes to either copy number or heterozygosity (P<0.02) in several independent experiments employing single-nucleotide polymorphism arrays. The reduction in copy-number changes, following shRNA treatment, was confirmed by Comparative Genome Hybridization analyses of the same DNA samples. Moreover, the chromosomal distributions of mutations correlated strongly with frequencies and locations of Alu interspersed repetitive elements on individual chromosomes. We conclude that the hsRAD51 protein level is systematically elevated in BAC, contributes significantly to genomic evolution during serial propagation of these cells and correlates with disease progression. Alu sequences may serve as substrates for elevated HR during cell proliferation in vitro, as they have been reported to do during the evolution of species, and thus may provide additional targets for prevention or treatment of this disease.

Contributions of the RAD51 N-terminal domain to BRCA2-RAD51 interaction

“…Crucial for maintenance of genomic integrity in normal cells, RAD51 allows the transformed or cancerous cells to develop resistance to radiation and DNA-damaging drugs used in chemotherapy. Elevated levels of RAD51 lead to rapid accumulation of genetic variation, genomic instability, acquisition of invasiveness, drug and radiation resistance and disease progression in many cancers including Barrett’s adenocarcenoma (62), multiple myeloma (63), recurrence of chronic myeloid leukemia (64), high grade gliomas (65) and lung cancer (66). Targeting RAD51 may therefore allow chemo- and radio-sensitization of cancerous cells as an adjuvant in standard combination anticancer regimens (67).…”

The role of inflammation in cancer of the esophagus

“…Expression of RAD51 is elevated in Barrett's adenocarcinoma cell lines and tissue specimens relative to normal cells, and its suppression was demonstrated to significantly prevent Barrett's adenocarcinoma cells from acquiring genomic changes to either copy number or heterozygosity in several independent experiments employing single-nucleotide polymorphism arrays [101]. It is therefore likely that hsRAD51 contributes significantly to genomic evolution during serial propagation of these cells and correlates with disease progression.…”

DNA repair targeted therapy: The past or future of cancer treatment?

“…Recent in vivo data incriminates Rad51 in promoting the formation of RNA-DNA hybrids which represent a potent source of altering genome structure and inducing chromosome instability (Wahba, Gore, & Koshland, 2013). In addition, increased Rad51 in multiple myeloma and esophageal adenocarcinoma was associated with elevated HR activity while knockdown of Rad51 prevented the acquisition of genomic changes (Shammas et al, 2009; Pal et al, 2011). Rad51 inhibition was shown to reduce breast cancer migration suggesting it contributes to metastases as well (Wiegmans et al, 2014).…”