ATM may be a protective factor in endometrial carcinogenesis with the progesterone pathway

Anti-Tumor Effect of Inhibition of DNA Damage Response Proteins, ATM and ATR, in Endometrial Cancer Cells

While the incidence of endometrial cancer continues to rise, the therapeutic options remain limited for advanced or recurrent cases, and most cases are resistant to therapy. The anti-tumor effect of many chemotherapeutic drugs and radiotherapy depends on the induction of DNA damage in cancer cells; thus, activation of DNA damage response (DDR) pathways is considered an important factor affecting resistance to therapy. When some DDR pathways are inactivated, inhibition of other DDR pathways can induce cancer-specific synthetic lethality. Therefore, DDR pathways are considered as promising candidates for molecular-targeted therapy for cancer. The crosstalking ataxia telangiectasia mutated and Rad3 related and checkpoint kinase 1 (ATR-Chk1) and ataxia telangiectasia mutated and Rad3 related and checkpoint kinase 2 (ATM-Chk2) pathways are the main pathways of DNA damage response. In this study, we investigated the anti-tumor effect of inhibitors of these pathways in vitro by assessing the effect of the combination of ATM or ATR inhibitors and conventional DNA-damaging therapy (doxorubicin (DXR), cisplatin (CDDP), and irradiation) on endometrial cancer cells. Both the inhibitors enhanced the sensitivity of cells to DXR, CDDP, and irradiation. Moreover, the combination of ATR and Chk1 inhibitors induced DNA damage in endometrial cancer cells and inhibited cell proliferation synergistically. Therefore, these molecular therapies targeting DNA damage response pathways are promising new treatment strategies for endometrial cancer.

Telomerase and Telomeres in Endometrial Cancer

Telomeres at the termini of human chromosomes are shortened with each round of cell division due to the “end replication problem” as well as oxidative stress. During carcinogenesis, cells acquire or retain mechanisms to maintain telomeres to avoid initiation of cellular senescence or apoptosis and halting cell division by critically short telomeres. The unique reverse transcriptase enzyme complex, telomerase, catalyzes the maintenance of telomeres but most human somatic cells do not have sufficient telomerase activity to prevent telomere shortening. Tissues with high and prolonged replicative potential demonstrate adequate cellular telomerase activity to prevent telomere erosion, and high telomerase activity appears to be a critical feature of most (80–90%) epithelial cancers, including endometrial cancer. Endometrial cancers regress in response to progesterone which is frequently used to treat advanced endometrial cancer. Endometrial telomerase is inhibited by progestogens and deciphering telomere and telomerase biology in endometrial cancer is therefore important, as targeting telomerase (a downstream target of progestogens) in endometrial cancer may provide novel and more effective therapeutic avenues. This review aims to examine the available evidence for the role and importance of telomere and telomerase biology in endometrial cancer.

Arecoline-regulated ataxia telangiectasia mutated expression level in oral cancer progression

BACKGROUND

Ataxia telangiectasia mutated (ATM) regulates DNA repair and cell cycle. The present study analyzed arecoline-induced ATM expression during oral cancer progression.

METHODS

In vitro studies were performed using oral squamous cell carcinoma (OSCC) cell lines treated with arecoline to analyze cell response and ATM regulation. in vivo studies were performed using immunohistochemistry to detect ATM expression in normal, oral potentially malignant disorder (OPMD), and OSCC tissues.

RESULTS

Low-dose arecoline induced cell proliferation, ATM promoter activity, and DNA repair. High-dose arecoline induced cell cycle arrest, apoptosis, and DNA damage. ATM was overexpressed in OPMD tissues but was downregulated in OSCC tissues. ATM expression level was associated with the risk of developing dysplasia, buccal-OSCC, and with OSCC survival rate.

CONCLUSION

High ATM expression helps DNA repair mechanisms to maintain the cells in the OPMD stage, but low ATM expression causes DNA damage accumulation to increase cell malignancy.

Expression of p53, Bcl-2 and Bax in endometrial carcinoma, endometrial hyperplasia and normal endometrium: a histopathological study

Our objective was to examine the expression rates of p53, Bcl-2 and Bax in endometrial carcinoma, endometrial hyperplasia and normal endometrium. A total of 94 endometrial frozen sections (carcinoma 48, hyperplasia 21, normal tissue 25) were examined immunohistochemically in terms of the expression rates of p53, Bcl-2 and Bax. All of the specimens in the non-malignant groups were positive for Bax, whereas this rate was 85.4% in the group with malignant specimens (p = .03). Conversely, p53 was expressed only in the cancerous group (77.1%, p < .001). The Bcl-2 expression rate was 54.2% in the cancer group, 76.2% in the group with hyperplasia and 60% in the group containing normal tissue (p = .23). Comparing to the non-malignant specimens, the mean Bcl-2/Bax were significantly higher in the malignant group. In conclusion, Bax under-expression, p53 over-expression and a high Bcl-2 to Bax ratio might be associated with endometrial carcinoma. Bcl-2, however, plays no significant role in this regard. Impact statement What is already known on this subject? The p53, Bcl-2 and Bax are the three major genes that regulate apoptosis. Some studies have suggested that these genes may play a role in the pathogenesis of endometrial carcinoma. The available reports, however, are old and inconclusive. What do the results of this study add? Comparing immunohistochemically obtained p53, the Bcl-2 and Bax expression rates between normal endometrial tissue, endometrial specimens with endometrial hyperplasia and specimens with carcinoma showed that Bax under-expression, p53 over-expression and a high Bcl-2 to Bax ratio were associated with malignancy. Using an up-to-date technique to examine the three major regulators of apoptosis at the same time, in a rather large sample size of both normal and abnormal endometrial tissue specimens simultaneously, are the major advantages of the present work. What are the implications of these findings for clinical practice and/or further research? According to our findings, the status of p53, Bcl-2 and Bax expression in the endometrial tissue can be used for risk stratification of endometrial carcinoma for both screening and preventive purposes.

Effect of ATM-111 (G>A) Polymorphism on Cancer Risk: A Meta-Analysis

OBJECTIVE

To assess the relationship between the ataxia telangiectasia mutated (ATM) gene-111 (G>A) polymorphism and cancer risk.

METHODS

The PubMed, EMBASE, Web of Science, and China National Knowledge Infrastructure databases were searched comprehensively. A total of 16 case-control studies with 12,273 cases and 13,046 controls were included in this meta-analysis; 12 of them were from the Chinese population. Five studies assessed smoking effects, including 3038 smokers and 1003 nonsmokers. Odds ratio (OR) was determined by using a genetic model-free approach. Heterogeneity was quantified by I(2) statistics. Publication bias was also evaluated.

RESULTS

The recessive model (AA vs. AG + GG) was suggested as the most appropriate genetic model. After elimination of heterogeneity, it was found that the ATM-111 (G>A) AA genotype is significantly associated with increased susceptibility to overall cancer risk in a fixed effects model (OR = 1.09; 95% CI = 1.03-1.15; p < 0.01; I(2) < 0.01). In the subgroup analysis, the result of pooled analyses among the Chinese population revealed similar associations (OR = 1.12; 95% CI = 1.04-1.22; p < 0.01; I(2) < 0.01). As for specific cancer analysis, an increase was correlated with lung cancer risk (OR = 1.12; 95% CI = 1.01-1.24; p = 0.03) and breast cancer risk (OR = 1.08; 95% CI = 1.00-1.16; p = 0.05). In addition, a stronger association was found among nonsmokers (OR = 1.31; 95% CI = 1.13-1.52; p < 0.01).

CONCLUSION

This meta-analysis suggests that AA genotype of the ATM-111 gene (G>A) may be a risk factor for breast cancer and lung cancer, especially among nonsmokers, within the Chinese population.