Expression of DNA mismatch repair gene MSH2 in cytological material from lung cancer patients

DNA mismatch repair (MMR) genes expression in lung cancer and its correlation with different clinicopathologic parameters

Lung cancer (LC) is a crucial rapidly developing disease. In Egypt, it is one of the five most frequent cancers. Little is known about the impact of deleted mismatch repair genes and its correlation to clinicopathological characteristics. This study evaluates immunohistochemical expression of the mismatch repair genes (PMS2), (MSH2), (MLH1) & (MSH6) & its correlation with clinicopathologic parameters & prognosis of LC. Age was higher with lost MLH1 & PMS2 but HTN was higher with lost four markers. Smoking was associated with expression of MLH1 & PMS2. A progressive course was associated with lost MSH2 & MSH6. Suprarenal metastasis was associated with lost all markers but bone metastasis was associated with lost MSH2 & MSH6. All the markers were significantly correlated with each other, with perfect correlations between MSH6 & MSH2 and between MLH & PMS2. Median overall survival among cases with lost markers was significantly lower than patients with preserved markers. We recommend evaluation of the four proteins as a biomarker that could guide LC therapy. In-depth biological research is imperative to elucidate the precise roles and mechanisms of these markers. This will advance management strategies and even guide immune checkpoint inhibitor therapy for LC.

Rediscovering immunohistochemistry in lung cancer

Several observations indicate that protein expression analysis by immunohistochemistry (IHC) remains relevant in individuals with non-small-cell lung cancer (NSCLC) when considering targeted therapy, as an early step in diagnosis and for therapy selection. Since the advent of next-generation sequencing (NGS), the role of IHC in testing for NSCLC biomarkers has been forgotten or ignored. We discuss how protein-level investigations maintain a critical role in defining sensitivity to lung cancer therapies in oncogene- and non-oncogene-addicted cases and in patients eligible for immunotherapy, suggesting that IHC testing should be reconsidered in clinical practice. We also argue how a panel of IHC tests should be considered complementary to NGS and other genomic assays. This is relevant to current clinical diagnostic practice but with potential future roles to optimize the selection of patients for innovative therapies. At the same time, strict validation of antibodies, assays, scoring systems, and intra- and interobserver reproducibility is needed.

Oxidative Stress and Deregulated DNA Damage Response Network in Lung Cancer Patients

The deregulated DNA damage response (DDR) network is associated with the onset and progression of cancer. Herein, we searched for DDR defects in peripheral blood mononuclear cells (PBMCs) from lung cancer patients, and we evaluated factors leading to the augmented formation of DNA damage and/or its delayed/decreased removal. In PBMCs from 20 lung cancer patients at diagnosis and 20 healthy controls (HC), we analyzed oxidative stress and DDR-related parameters, including critical DNA repair mechanisms and apoptosis rates. Cancer patients showed higher levels of endogenous DNA damage than HC (p < 0.001), indicating accumulation of DNA damage in the absence of known exogenous genotoxic insults. Higher levels of oxidative stress and apurinic/apyrimidinic sites were observed in patients rather than HC (all p < 0.001), suggesting that increased endogenous DNA damage may emerge, at least in part, from these intracellular factors. Lower nucleotide excision repair and double-strand break repair capacities were found in patients rather than HC (all p < 0.001), suggesting that the accumulation of DNA damage can also be mediated by defective DNA repair mechanisms. Interestingly, reduced apoptosis rates were obtained in cancer patients compared with HC (p < 0.001). Consequently, the expression of critical DDR-associated genes was found deregulated in cancer patients. Together, oxidative stress and DDR-related aberrations contribute to the accumulation of endogenous DNA damage in PBMCs from lung cancer patients and can potentially be exploited as novel therapeutic targets and non-invasive biomarkers.

Two co-existing germline mutations P53 V157D and PMS2 R20Q promote tumorigenesis in a familial cancer syndrome

Germline mutations are responsible for familial cancer syndromes which account for approximately 5-10% of all types of cancers. These mutations mainly occur at tumor suppressor genes or genome stability genes, such as DNA repair genes. Here we have identified a cancer predisposition family, in which eight members were inflicted with a wide spectrum of cancer including one diagnosed with lung cancer at 22years old. Sequencing analysis of tumor samples as well as histologically normal specimens identified two germline mutations co-existing in the familial cancer syndrome, the mutation of tumor suppressor gene P53 V157D and mismatch repair gene PMS2 R20Q. We further demonstrate that P53 V157D and/or PMS2 R20Q mutant promotes lung cancer cell proliferation. These two mutants are capable of promoting colony formation in soft agar as well as tumor formation in transgenic drosophila system. Collectively, these data have uncovered the important role of co-existing germline P53 and PMS2 mutations in the familial cancer syndrome development.

miR-21 induces cell cycle at S phase and modulates cell proliferation by down-regulating hMSH2 in lung cancer

PURPOSE

MicroRNAs regulate critical genes associated with lung cancer. Human mutS homolog 2 (hMSH2), one of the core mismatch repair genes, is affected in lung cancer development. The aim of this study is to investigate the role of miR-21 in hMSH2 gene expression and the effect of miR-21 on cell proliferation and cell cycle in lung cancer.

METHODS

The targets of miR-21 were predicted by a bioinformatics tool, and hMSH2 was validated as a direct target of miR-21 by luciferase activity assay. MiRNA mimics or inhibitors were used to stimulate or attenuate the effect of endogenous miR-21 on hMSH2 expression. MiR-21 and hMSH2 expressions were assessed with real-time RT-PCR and Western blotting. Cell cycle was determined by flow cytometry, and cell growth was analyzed by MTT assay and real-time cell analysis system.

RESULTS

MiR-21 expression was inversely correlated with hMSH2 expression in human lung cancer cell lines. Further validation showed hMSH2 was directly regulated by miR-21. The up-regulation of miR-21 significantly promoted cell proliferation and revealed a higher proportion of cells at S phase. However, knockdown of miR-21 expression resulted in cell cycle arrest at G2/M phase and inhibited cell proliferation.

CONCLUSIONS

These data suggest miR-21 is a key regulator of hMSH2 and modulates cell cycle and proliferation by targeting hMSH2 in human lung cancer.

The potential of exploiting DNA-repair defects for optimizing lung cancer treatment

The tumor genome is commonly aberrant as a consequence of mutagenic insult and incomplete DNA repair. DNA repair as a therapeutic target has recently received considerable attention owing to the promise of drugs that target tumor-specific DNA-repair enzymes and potentiate conventional cytotoxic therapy through mechanism-based approaches, such as synthetic lethality. Treatment for non-small-cell lung cancer (NSCLC) consists mainly of platinum-based chemotherapy regimens and improvements are urgently needed. Optimizing treatment according to tumor status for DNA-repair biomarkers, such as ERCC1, BRCA1 or RRM1, could predict response to platinum, taxanes and gemcitabine-based therapies, respectively, and might improve substantially the response of individual patients' tumors. Finally, recent data on germline variation in DNA-repair genes may also be informative. Here, we discuss how a molecular and functional DNA-repair classification of NSCLC may aid clinical decision making and improve patient outcome.

Phenotypic mismatch repair hMSH2 and hMLH1 gene expression profiles in primary non-small cell lung carcinomas

BACKGROUND

Defects in the human DNA mismatch repair genes (MMR) hMSH2 and hMLH1 are responsible for the development of sporadic and hereditary colorectal cancers. The role of MMR genes in the pathogenesis of lung cancer has not been elucidated. The aim of this study was to address the phenotypic mRNA expression profiles of mismatch DNA repair system in lung cancer.

MATERIALS AND METHODS

We evaluated the mRNA levels of the hMSH2 and hMLH1 components of the mismatch DNA repair (MMR) system in 29 unselected frozen pairs of primary non-small cell lung carcinomas (NSCLCs) and their adjacent normal tissue (ANTs) specimens by quantitative real-time PCR analysis relative to housekeeping Porphobilinogen deaminase (hPBGD) mRNA. To simplify and potentially improve the analysis of data, we defined for each individual MMR mRNA two possible phenotypes: a regular (R(2): hMSH2/hPBGD mRNAs> or =1 and R(1): hMLH1/hPBGD mRNAs> or =1) and a reduced (r(2): hMSH2/hPBGD mRNAs<1 and r(1): hMLH1/hPBGD mRNAs<1). The presence of MMR gene expression was evaluated after conversion of the molecular mRNA levels into clinically distinct phenotypic entities by these working criteria, based on the hypothesis that reduced mRNA and protein levels result in lower or non-functional MMR.

RESULTS

Phenotyping defined four distinct MMR system expression profiles, R(2)R(1), r(2)R(1), R(2)r(1) and r(2)r(1) by ascending tumor progression rate and identified a previously unrecognized disease-associated phenotypic entity (r(2)r(1)). The phenotype-based biological aspects of the MMR system suggested that its two components: (1) function independently and (2) are not directly involved in the onset of the transformation process, since healthy lung tissue was devoid of r(2)r(1) phenotypes.

CONCLUSION

These findings link MMR mRNA levels of paired lung tissue specimens to patients' clinical condition and suggest that phenotypic translation of molecular MMR data refines the biology of the MMR system with consequent diagnostic implications in the clinical assessment of lung cancer patients.

Gene expression profiling for molecular distinction and characterization of laser captured primary lung cancers

Methods

We examined gene expression profiles of tumor cells from 29 untreated patients with lung cancer (10 adenocarcinomas (AC), 10 squamous cell carcinomas (SCC), and 9 small cell lung cancer (SCLC)) in comparison to 5 samples of normal lung tissue (NT). The European and American methodological quality guidelines for microarray experiments were followed, including the stipulated use of laser capture microdissection for separation and purification of the lung cancer tumor cells from surrounding tissue.

Results

Based on differentially expressed genes, different lung cancer samples could be distinguished from each other and from normal lung tissue using hierarchical clustering. Comparing AC, SCC and SCLC with NT, we found 205, 335 and 404 genes, respectively, that were at least 2-fold differentially expressed (estimated false discovery rate: < 2.6%). Different lung cancer subtypes had distinct molecular phenotypes, which also reflected their biological characteristics. Differentially expressed genes in human lung tumors which may be of relevance in the respective lung cancer subtypes were corroborated by quantitative real-time PCR.

Genetic programming (GP) was performed to construct a classifier for distinguishing between AC, SCC, SCLC, and NT. Forty genes, that could be used to correctly classify the tumor or NT samples, have been identified. In addition, all samples from an independent test set of 13 further tumors (AC or SCC) were also correctly classified.

Conclusion

The data from this research identified potential candidate genes which could be used as the basis for the development of diagnostic tools and lung tumor type-specific targeted therapies.