Correlations between Risk Factors for Breast Cancer and Genetic Instability in Cancer Patients-A Clinical Perspective Study

DNA base oxidation in relation to TNM stages and chemotherapy treatment in colorectal cancer patients 2-9 months post-surgery

Accumulation of DNA damage is a critical feature of genomic instability, which is a hallmark of various cancers. The enzyme-modified comet assay is a recognized method to detect specific DNA lesions at the level of individual cells. In this cross-sectional investigation, we explore possible links between clinicopathological and treatment related factors, nutritional status, physical activity and function, and DNA damage in a cohort of colorectal cancer (CRC) patients with non-metastatic disease. Levels of DNA damage in peripheral mononuclear blood cells (PBMCs) assessed 2-9 months post-surgery, were compared across tumour stage (localized (stage I-II) vs. regional (stage III) disease), localization (colon vs. rectosigmoid/rectum cancer), and adjuvant chemotherapy usage, with the last dosage administrated 2-191 days prior to sampling. Associations between DNA damage and indicators of nutritional status, physical activity and function were also explored. In PBMCs, DNA base oxidation was higher in patients diagnosed with regional compared with localized tumours (P = 0.03), but no difference was seen for DNA strand breaks (P > 0.05). Number of days since last chemotherapy dosage was negatively associated with DNA base oxidation (P < 0.01), and patients recently receiving chemotherapy (<15 days before blood collection) had higher levels of DNA base oxidation than those not receiving chemotherapy (P = 0.03). In the chemotherapy group, higher fat mass (in kg and %) as well as lower physical activity were associated with greater DNA base oxidation (P < 0.05). In conclusion, DNA base oxidation measured with the enzyme-modified comet assay varies according to tumour and lifestyle related factors in CRC patients treated for non-metastatic disease.

Harnessing Epigenetics for Breast Cancer Therapy: The Role of DNA Methylation, Histone Modifications, and MicroRNA

Breast cancer exhibits various epigenetic abnormalities that regulate gene expression and contribute to tumor characteristics. Epigenetic alterations play a significant role in cancer development and progression, and epigenetic-targeting drugs such as DNA methyltransferase inhibitors, histone-modifying enzymes, and mRNA regulators (such as miRNA mimics and antagomiRs) can reverse these alterations. Therefore, these epigenetic-targeting drugs are promising candidates for cancer treatment. However, there is currently no effective epi-drug monotherapy for breast cancer. Combining epigenetic drugs with conventional therapies has yielded positive outcomes and may be a promising strategy for breast cancer therapy. DNA methyltransferase inhibitors, such as azacitidine, and histone deacetylase inhibitors, such as vorinostat, have been used in combination with chemotherapy to treat breast cancer. miRNA regulators, such as miRNA mimics and antagomiRs, can alter the expression of specific genes involved in cancer development. miRNA mimics, such as miR-34, have been used to inhibit tumor growth, while antagomiRs, such as anti-miR-10b, have been used to inhibit metastasis. The development of epi-drugs that target specific epigenetic changes may lead to more effective monotherapy options in the future.

Radiation increases COL1A1, COL3A1, and COL1A2 expression in breast cancer

Background

Radiotherapy-associated secondary cancer is an important issue for the treatment of breast cancer (BCa). This study aimed to investigate the molecular mechanism and genetic risk factors for radiation-associated secondary diseases in BCa.

Methods

The differentially expressed genes (DEGs) between preradiation and postradiation BCa samples in the GSE65505 dataset were obtained. The pathways related to the radiation-associated DEGs in the protein–protein interaction (PPI) network modules were identified. miRNAs targeted to the key genes in the PPI network were identified, and their association with BCa prognosis was analyzed.

Results

A total of 136 radiation-associated DEGs preradiation and postradiation BCa samples were screened out. The PPI network consisted of a significant module that consisted of 21 upregulated DEGs that were associated with “hsa04512: ECM–receptor interaction,” “hsa04151: PI3K-Akt signaling pathway,” and “hsa04115: p53 signaling pathway.” Sixteen DEGs, including three collagen genes collagen type I alpha 1 chain (COL1A1), COL3A1, and COL1A2, were enriched in 17 radiation-associated pathways. The three genes were upregulated in BCa tissues compared with controls and were also elevated by radiation. They were targeted by hsa-miR-29a/c, and the expression levels of hsa-miR-29a/c were associated with a poor prognosis of BCa.

Conclusions

The upregulation of COL1A1, COL3A1, and COL1A2 might be genetic risk factors for radiation-associated secondary diseases in BCa.

Association between single nucleotide polymorphisms of DNA damage response pathway genes and increased risk in breast cancer

Aim: We aimed to evaluate the role of selected single nucleotide polymorphisms of DNA damage response pathway genes in breast cancer (BC). Materials & methods: In present study, 500 BC patients and 500 controls was used to estimate the frequency of single nucleotide polymorphisms of DNA damage response pathway genes. Tetra-amplification refractory mutation system-PCR technique was used for screening of the six selected polymorphisms. Results: Logistic regression analysis showed that heterozygous mutant genotype of rs1800057 (p < 0.0001) and homozygous mutant genotype of rs1801516 (p < 0.0001) was associated with significant increased risk of BC. In the ATR gene, heterozygous mutant genotype of rs2227931 (p < 0.0001) was associated with significant increased risk of BC. However, significant decreased risk of BC was found associated with heterozygous mutant genotype of rs2227928 (p < 0.0002) and homozygous mutant genotype of rs2229032 (p < 0.0001) in patients compared with controls. Conclusion: The present results showed that alteration in DNA damage response pathway gene (ATM & ATR) results in increased BC risk.

Effect of the thymine-DNA glycosylase rs4135050 variant on Saudi smoker population

Background

Thymine‐DNA glycosylase (TDG) is an essential DNA‐repair enzyme which works in both epigenetic regulation and genome maintenance. It is also responsible for efficient correction of multiple endogenous DNA lesions which occur commonly in mammalian genomes. Research of genetic variants such as SNPs, resulting in disease, is predicted to yield clinical advancements through the identification of sensitive genetic markers and the development of disease prevention and therapy. To that end, the main objective of the present study is to identify the possible interactions between cigarette smoking and the rs4135050 variant of the TDG gene, situated in the intron position, among Saudi individuals.

Methods

TDG rs4135050 (A/T) was investigated by genotyping 239, and 235 blood specimens were obtained from nonsmokers and smokers of cigarette respectively.

Results

T allele frequency was found which showed a significant protective effect on Saudi male smokers (OR = 0.64, p = 0.0187) compared to nonsmoking subjects, but not in female smokers. Furthermore, smokers aged less than 29 years, the AT and AT+TT genotypes decreased more than four times the risk of initiation of smoking related‐diseases compare to the ancestral AA homozygous genotype. Paradoxically, the AT (OR = 3.88, p = 0.0169) and AT+TT (OR = 2.86, p = 0.0420) genotypes were present at a higher frequency in smoking patients aged more than 29 years as compared to nonsmokers at the same ages.

Conclusion

Depending on the gender and age of patients, TDG rs4135050 may provide a novel biomarker for the early diagnosis and prevention of several diseases caused by cigarette smoking.

Toxicogenetic study of omeprazole and the modulatory effects of retinol palmitate and ascorbic acid on Allium cepa

Omeprazole (OME) is a proton pump inhibitor used for the treatment of various gastric and intestinal disease; however, studies on its effects on the genetic materials are still restricted. The present study aimed to evaluate possible toxicogenic effects of OME in Allium cepa meristems with the application of cytogenetic biomarkers for DNA damage, mutagenic, toxic and cytotoxic effects. Additionally, retinol palmitate (RP) and ascorbic acid (AA) were also co-treated with OME to evaluate possible modulatory effects of OME-induced cytogenetic damages. OME was tested at 10, 20 and 40 μg/mL, while RP and AA at 55 μg/mL and 352.2 μg/mL, respectively. Copper sulphate (0.6 μg/mL) and dechlorinated water were used as positive control and negative control, respectively. The results suggest that OME induced genotoxicity and mutagenicity in A. cepa at all tested concentrations. It was noted that cotreatment of OME with the antioxidant vitamins RP and/or AA significantly (p < 0.05) inhibited and/or modulated all toxicogenic damages induced by OME. These observations demonstrate their antigenotoxic, antimutagenic, antitoxic and anticitotoxic effects in A. cepa. This study indicates that application of antioxidants may be useful tools to overcome OME-induced toxic effects.