Chronic hypoxia is associated with transcriptomic reprogramming and increased genomic instability in cancer cells.

Hypoxia afflicts the microenvironment of solid tumors fueling malignancy. We investigated the impact of long hypoxia exposure on transcriptional remodeling, tumor mutational burden (TMB), and genomic instability of cancer cells that were grouped based on their inherent sensitivity or resistance to hypoxia. A hypoxia score was used as a metric to distinguish between the most hypoxia-sensitive (hypoxia high (HH)), and most resistant (hypoxia low (HL)) cancer cells. By applying whole exome sequencing and microarray analysis, we showed that the HH group was indeed more sensitive to hypoxia, having significantly higher TMB (p = 0.03) and copy number losses (p = 0.03), as well as a trend of higher transcriptional response. Globally cells adapted by decreasing expression of genes involved in metabolism, proliferation, and protein maturation, and increasing alternative splicing. They accumulated mutations, especially frameshift insertions, and harbored increased copy number alterations, indicating increased genomic instability. Cells showing highest TMB simultaneously experienced a significant downregulation of DNA replication and repair and chromosomal maintenance pathways. A sixteen-gene common response to chronic hypoxia was put forth, including genes regulating angiogenesis and proliferation. Our findings show that chronic hypoxia enables survival of tumor cells by metabolic reprogramming, modulating proliferation, and increasing genomic instability. They additionally highlight key adaptive pathways that can potentially be targeted to prevent cancer cells residing in chronically hypoxic tumor areas from thriving.

p53 reactivating small molecule PRIMA­1MET/APR­246 regulates genomic instability in MDA­MB­231 cells.

Pharmacological reactivation of tumor­suppressor protein p53 has acted as a promising strategy for more than 50% of human cancers that carry a non­functional mutant p53 (mutp53). p53 plays a critical role in preserving genomic integrity and DNA fidelity through numerous biological processes, including cell cycle arrest, DNA repair, senescence and apoptosis. By contrast, non­functional mutp53 compromises the aforementioned genome stabilizing mechanisms through gain of function, thereby increasing genomic instability in human cancers. Restoring the functional activity of p53 using both genetic and pharmacological approaches has gained prominence in targeting p53­mutated tumors. Thus, the present study aimed to investigate the reactivation of p53 in DNA repair mechanisms and the maintenance of genomic stability using PRIMA­1MET/APR­246 small molecules, in both MDA­MB­231 and MCF­7 breast cancer cell lines, which carry mutp53 and wild­type p53, respectively. Results of the present study revealed that reactivation of p53 through APR­246 led to an increase in the functional activity of DNA repair. Prolonged treatment of MDA­MB­231 cells with APR­246 in the presence of cisplatin led to a reduction in mutational accumulation, compared with cells treated with cisplatin alone. These findings demonstrated that APR­246 may act as a promising small molecule to control the genomic instability in p53­mutated tumors.