Genetic Polymorphism, Telomere Biology and Non-Small Lung Cancer Risk

Association and causal impact of TERT genetic variants on peripheral blood leukocyte telomere length and cerebral small vessel disease risk in a Chinese Han population: a mendelian randomization analysis

BACKGROUND

Previous observational studies have highlighted potential relationships between the telomerase reverse transcriptase (TERT) gene, short leukocyte telomere length (LTL), and cerebrovascular disease. However, it remains to be established as to whether TERT gene variants are associated with an elevated risk of cerebral small vessel disease (CSVD), and whether there is a causal relationship between LTL and CSVD.

METHODS

Five TERT single nucleotide polymorphisms (SNPs) were analyzed in 307 CSVD patients and 320 healthy controls in whom LTL values were quantified. Allele models and four genetic models were used to explore the relationship between these SNP genotypes and CSVD risk. A Mendelian randomization analysis of CSVD risk was then performed using LTL-related SNPs and the polygenic risk score (PRS) constructed from these SNPs as genetic instrumental variables to predict the causal relationship between LTL and CSVD risk.

RESULTS

Model association analyses identified two SNPs that were significantly associated with CSVD risk. LTL was significantly correlated with age (P < 0.001), and the MR analysis revealed an association between short LTL and an elevated risk of CSVD. PRS-based genetic prediction of short LTLs was also significantly related to an elevated CSVD risk.

CONCLUSION

Multiple genetic models and MR results indicate that TERT gene SNPs may be related to an elevated risk of CSVD, and that shorter LTL may be causally linked to such CSVD risk.

Single-Cell RNA Sequencing: Technological Progress and Biomedical Application in Cancer Research

Single-cell RNA-seq (scRNA-seq) is a revolutionary technology that allows for the genomic investigation of individual cells in a population, allowing for the discovery of unusual cells associated with cancer and metastasis. ScRNA-seq has been used to discover different types of cancers with poor prognosis and medication resistance such as lung cancer, breast cancer, ovarian cancer, and gastric cancer. Besides, scRNA-seq is a promising method that helps us comprehend the biological features and dynamics of cell development, as well as other disorders. This review gives a concise summary of current scRNA-seq technology. We also explain the main technological steps involved in implementing the technology. We highlight the present applications of scRNA-seq in cancer research, including tumor heterogeneity analysis in lung cancer, breast cancer, and ovarian cancer. In addition, this review elucidates potential applications of scRNA-seq in lineage tracing, personalized medicine, illness prediction, and disease diagnosis, which reveals that scRNA-seq facilitates these events by producing genetic variations on the single-cell level.

Genetic variants in NPAS2 gene and clinical outcomes of resectable non-small-cell lung cancer

Background: A series of studies have demonstrated that NPAS2 plays a critical role in the development and progression of several cancers. However, the association between genetic variants in the NPAS2 gene and the clinical outcome of patients with non-small-cell lung cancer (NSCLC) has not been investigated. Methods: Six functional SNPs in NPAS2 were selected and genotyped using the Sequenom iPLEX genotyping system in a cohort of 484 Chinese NSCLC patients undergoing surgery. Multivariate Cox proportional hazards model were used for the prognosis analysis. Results: We found that SNP rs2305158 exhibited a significant association with overall survival of NSCLC patients in the dominant model (hazard ratio [HR]: 0.68; 95% CI: 0.49-0.95; p = 0.02). Lymph node metastasis was significantly associated with increased death risk (HR: 1.73; 95% CI: 1.24-2.40; p = 0.001) in patients with the homozygous wildtype (WW) genotype of rs2305158. However, no significant association was observed between them in patients carrying a heterozygous variant (WV) or homozygous variant (VV) genotype of rs2305158. Finally, in the joint and interaction analysis, the patients carrying homozygous wildtype (WW) genotype and lymph node metastasis from N1 to N3 conferred a significant increased effect on death (HR: 2.29; 95% CI: 1.40-3.76; p = 0.001). Conclusions: Our results suggest that NPAS2 polymorphisms may serve as an independent prognostic marker for NSCLC patients.

Telomere-associated genes and telomeric lncRNAs are biomarker candidates in lung squamous cell carcinoma (LUSC)

In the past decade, research efforts were made to identify molecular biomarkers useful as therapeutic targets in Non-Small Cell Lung Cancer (NSCLC), the most frequent type of lung carcinoma. NSCLC presents different histological subtypes being the most prevalent LUSC (Lung Squamous Cell Cancer) and LUAD (Lung Adenocarcinoma), and only a subset of LUAD patients' present tumors expressing known targetable genetic alterations. Telomeres and its components, including telomerase, the enzyme that replenishes telomeres, have been considered potential cancer biomarkers due to their crucial role in cell proliferation and genome stability. Our study aims to quantify expression changes affecting telomere-associated genes and ncRNAs associated with telomere regulation and maintenance in NSCLC. We first assessed the transcriptome (RNA-Seq) data of NSCLC patients from The Cancer Genome Atlas (TCGA) and then we tested the expression of telomere-associated genes and telomeric ncRNAs (TERC, telomerase RNA component, and TERRA, telomere repeat-containing RNA) in Brazilian NCSLC patient samples by quantitative RT-PCR, using matched normal adjacent tissue samples as the control. We also estimated the mean size of terminal restriction fragments (TRF) of some Brazilian NSCLC patients using telomeric Southern blot. The TCGA analysis identified alterations in the expression profile of TERT and telomere damage repair genes, mainly in the LUSC subtype. The study of Brazilian NSCLC samples by RT-qPCR showed that LUSC and LUAD express high amounts of TERT and that although the mean TRF size of tumor samples was shorter compared to normal cells, telomeres in NSCLC are probably maintained by telomerase. Also, the expression analysis of Brazilian NSCLC samples identified statistically significant alterations in the expression of genes involved with telomere damage repair, as well as in TERC and TERRA, mainly in the LUSC subtype. We, therefore, concluded that telomere maintenance genes are significantly deregulated in NSCLC, representing potential biomarkers in the LUSC subtype.

Effect of alcohol use disorder on cellular aging

RATIONALE

Human telomeres consist of tandem repeats at chromosome ends which protect chromosomal DNA from degradation. Telomere shortening occurs as part of natural aging; however, life stressors, smoking, drug use, BMI, and psychiatric disorders could disrupt cell aging and affect telomere length (TL). In this context, studies have evaluated the effects of alcohol consumption on TL; however, results have been inconsistent, which may reflect diverse drinking cut-offs and categorizations.

OBJECTIVES

To help clarify this, the present study addresses the association of TL with alcohol use disorder (AUD), drinking behaviors, lifetime stress, and chronological age.

METHODS

TL was quantified as the telomere to albumin ratio (T/S ratio) obtained from peripheral blood DNA using the quantitative PCR assay, from 260 participants with AUD and 449 non-dependent healthy controls (HC) from an existing National Institute on Alcohol Abuse and Alcoholism (NIAAA) database.

RESULTS

AUD participants showed shorter TL compared to HC with both, age, and AUD, as independent predictors as well as a significant AUD with age interaction effect on TL. TL was also associated with impulsiveness in AUD participants. We did not observe an association between TL and chronicity of alcohol use, alcohol doses ingested, or childhood trauma exposures in either AUD or HC, although very few HC reported a history of childhood trauma.

CONCLUSION

Our results support previous findings of telomere shortening with chronic alcohol exposures and show both an effect of AUD on TL that is independent of age as well as a significant AUD by age interaction on TL. These findings are consistent with accelerated cellular aging in AUD.

Association between hTERT Polymorphisms and Female Papillary Thyroid Carcinoma

BACKGROUND

A previous genome-wide association study showed that hTERT rs10069690 and rs2736100 polymorphisms were associated with thyroid cancer risk.

OBJECTIVE

This study further investigated the association between increased risk and clinicopathologic characteristics for Papillary Thyroid Carcinoma (PTC) and hTERT polymorphisms rs10069690 or rs2736100 in a Chinese female population.

METHODS

The hTERT genotypes of 276 PTC patients and 345 healthy subjects were determined with regard to SNPs rs10069690 and rs2736100. The association between these SNPs and the risk of PTC and clinicopathologic characteristics was investigated by logistic regression.

RESULTS

We found a significant difference between PTC and rs10069690 (Odds Ratio (OR) = 1.515; P = 0.005), but not between PTC and rs2736100. When the analysis was limited to females, rs10069690 and rs2736100 were both associated with increased risk for PTC in female individuals (OR = 1.647, P = 0.007; OR = 1.339, P = 0.041, respectively). Further haplotype analysis revealed a stimulative effect of haplotypes TC and CA of TERT rs10069690-rs2736100, which increased risk for PTC in female individuals (OR = 1.579, P = 0.014; OR = 0.726, P = 0.025, respectively). Furthermore, the heterozygote A/C of rs2736100 showed significant difference for age (OR = 0.514, P = 0.047).

CONCLUSION

Our finding suggests that hTERT polymorphisms rs10069690 and rs2736100 are associated with increased risk for PTC in Chinese female population and rs2736100 may be related to age. Consistent with US20170360914 and US20170232075, they are expected to be a potential molecular target for anti-cancer therapy.

Effect of FAM196B in human lung adenocarcinoma

Lung cancer is the leading cause of cancer-related mortality worldwide. The present study focused on the function of family with sequence similarity 196 member B (FAM196B) in lung adenocarcinoma (LUAD). We analyzed lung carcinoma patients' data from the Cancer Genome Atlas (TCGA), and verify the change of FAM196B expression in 30 LUAD tissues and matched adjacent non-tumor tissues (> 5 cm) by tissue microarray. To investigate the role of FAM196B in LUAD, we used lentivirus-mediated short hairpin RNA (shRNA) to knockdown FAM196B expression in human LUAD cell line A549 and H1299 and assessed it by RT-qPCR and western blot. Celigo Imaging Cytometry System, MTT assays and colony formation were conducted to evaluate cell proliferation. Cell apoptosis were assayed by Annexin V staining. We found that FAM196B was significantly upregulated (P=5.06E-06) in LUAD compared with adjacent non-tumor tissues. Cell proliferation was inhibited in FAM196B-silenced A549 and H1299 cells using Celigo Imaging Cytometry System, MTT assays and colony formation assays. Apoptosis rate was significantly increased in FAM196B-shRNA group than the control group. In conclusion, Knockdown of FAM196B can inhibit cell proliferation, cell colony formation capacity, and promote cell apoptosis in A549 and H1299 cell lines. FAM196B may be one novel potential targets for treating patients with LUAD.

Telomerase Reverse Transcriptase Polymorphism rs2736100: A Balancing Act between Cancer and Non-Cancer Disease, a Meta-Analysis

The enzyme telomerase reverse transcriptase (TERT) is essential for telomere maintenance. In replicating cells, maintenance of telomere length is important for the preservation of vital genetic information and prevention of genomic instability. A common genetic variant in TERT, rs2736100 C/A, is associated with both telomere length and multiple diseases. Carriage of the C allele is associated with longer telomere length, while carriage of the A allele is associated with shorter telomere length. Furthermore, some diseases have a positive association with the C and some with the A allele. In this study, meta-analyses were performed for two groups of diseases, cancerous diseases, e.g., lung cancer and non-cancerous diseases, e.g., pulmonary fibrosis, using data from genome-wide association studies and case-control studies. In the meta-analysis it was found that cancer positively associated with the C allele (pooled OR 1.16 [95% CI 1.09–1.23]) and non-cancerous diseases negatively associated with the C allele (pooled OR 0.81 [95% CI 0.65–0.99]). This observation illustrates that the ambiguous role of telomere maintenance in disease hinges, at least in part, on a single locus in telomerase genes. The dual role of this single nucleotide polymorphism also emphasizes that therapeutic agents aimed at influencing telomere maintenance should be used with caution.

Primary pulmonary lymphoepithelioma-like carcinoma in Singapore

BACKGROUND

Primary pulmonary lymphoepithelioma-like carcinoma (PPLELC) is a rare subtype of nonsmall cell lung cancer (NSCLC) predominantly reported in East Asia. We aimed to evaluate clinical characteristics, diagnosis, treatment, and prognosis of PPLELC in Singapore.

METHODS

Retrospective review of all patients diagnosed with PPLELC at our center between 2000 and 2014.

RESULTS

All 28 patients were Chinese, 67.9% were female, and the median age was 58 years (range37-76 years). Majority (89.3%) were never smokers and 53.6% asymptomatic at diagnosis. About 28.6% presented with Stage I/II disease, 25% had Stage III disease, and 46.4% had Stage IV disease. All patients with Stage I/II disease underwent lobectomy without adjuvant treatment. Four out of 7 patients with Stage III disease underwent surgery with or without adjuvant therapy while the rest received chemoradiation. Twelve out of 13 patients with Stage IV disease received chemotherapy with or without radiotherapy. At the end of 2016, survival data were available for all 28 patients. Two-year survival rates for Stage I/II, Stage III, and Stage IV disease were 100%, 85.7%, and 61.5%, respectively, while survival was 100%, 85.7%, and 9.6%, respectively, at five years.

CONCLUSION

The majority (46.4%) of patients presented with metastatic disease. For those with Stage I-III disease, 5-year survival for PPLELC was better than other NSCLC subtypes. Multimodality treatment including surgery could be considered in locally advanced disease. In Stage IV disease, it tended to approximate that of NSCLC.

Role of microRNA-21 in radiosensitivity in non-small cell lung cancer cells by targeting PDCD4 gene

This study aims to explore the effects of microRNA-21 (miR-21) on radiosensitivity in non-small cell lung cancer (NSCLC) by targeting programmed cell deanth 4 (PDCD4) and regulating PI3K/AKT/mTOR signaling pathway. Cancer tissues and adjacent normal tissues were collected from 97 NSCLC patients who received a standard radiotherapy regimen. TUNEL assay was applied to determine cell apoptosis in tissues. The qRT-PCR assay was used to detect the expressions of miR-21 expression and PDCD4 mRNA. The protein expressions of PDCD4 and PI3K/AKT/mTOR signaling pathway-related proteins were determined by Western blotting. Colony formation assay was used to observe the sensitivity to radiotherapy of NSCLC cells. Flow cytometry was adopted to testify cell apoptosis. Compared with adjacent normal tissues, miR-21 expression was significantly increased and the mRNA and protein expressions of PDCD4 were decreased in NSCLC tissues. Higher miR-21 expression was associated with attenuated radiation efficacy and shorter median survival time. PDCD4 was the target gene of miR-21. The miR-21 mimics and siRNA-PDCD4 decreased the sensitivity to radiotherapy and cell apoptosis of A549 and H1299 cells and activated PI3K/AKT/mTOR pathway. The sensitivity of A549 and H1299 cells was strengthened in the miR-21 inhibitors group and the PI3K/AKT/mTOR inhibitors group. The siRNA-PDCD4 could reverse the effects of miR-21 inhibitors on sensitivity to radiotherapy and cell apoptosis of NSCLC cells. Our findings provide strong evidence that miR-21 could inhibit PDCD4 expression and activate PI3K/AKT/mTOR signaling pathway, thereby affecting the radiation sensitivity of NSCLC cells.

P53-dependent downregulation of hTERT protein expression and telomerase activity induces senescence in lung cancer cells as a result of pterostilbene treatment

Cellular senescence is characterized by permanent cell cycle arrest, triggered by a variety of stresses, such as telomerase inhibition, and it is recognized as a tumor-suppressor mechanism. In recent years, telomerase has become an important therapeutic target in several cancers; inhibition of telomerase can induce senescence via the DNA damage response (DDR). Pterostilbene (PT), a dimethyl ether analog of resveratrol, possesses a variety of biological functions, including anticancer effects; however, the molecular mechanisms underlying these effects are not fully understood. In this study, we investigated the possible mechanisms of PT-induced senescence through telomerase inhibition in human non-small cell lung cancer cells and delineated the role of p53 in senescence. The results indicated that PT-induced senescence is characterized by a flattened morphology, positive staining for senescence-associated-β galactosidase activity, and the formation of senescence-associated heterochromatic foci. Telomerase activity and protein expression was significantly decreased in H460 (p53 wild type) cells compared with H1299 (p53 null) cells and p53 knockdown H460 cells (H460-p53-). A more detailed mechanistic study revealed that PT-induced senescence partially occurred via a p53-dependent mechanism, triggering inhibition of telomerase activity and protein expression, and leading to the DDR, S phase arrest and, finally, cellular senescence. This study is the first to explore the novel anticancer mechanism of PT senescence induction via the inhibition of telomerase in lung cancer cells.

miR-103 Functions as a Tumor Suppressor by Directly Targeting Programmed Cell Death 10 in NSCLC

Non-small cell lung cancer (NSCLC) accounts for about 85% of all lung cancer cases. Absence of miR-103 has recently been identified to be associated with metastatic capacity of primary lung tumors. However, the exact role of miR-103 in NSCLC and the molecular mechanism are unclear. In the present study, we showed that miR-103 expression was reduced in NSCLC tissues and cells. miR-103 expression was negatively correlated with tumor size and stage. The overall survival was longer in patients with higher miR-103 level than in those with lower miR-103 expression. miR-103 inhibited cell proliferation in A549 cells, decreased tumor weight and volume, and prolonged survival of tumor-implanted nude mice. miR-103 increased apoptotic cell death in A549 cells. Furthermore, miR-103 decreased the invasion and migration abilities in A549 cells, as evidenced by Transwell and wound healing results. Downregulation of miR-103 significantly reduced the level of programmed cell death 10 (PDCD10). We found a significant decrease in the relative luciferase activity of the reporter gene in A549 cells cotransfected with the miR-103 mimic and pGL3-PDCD10 WT 3′-UTR, but not pGL3-PDCD10 mut 3′-UTR. We showed that overexpression of PDCD10 significantly inhibited miR-103-induced inhibition of cell proliferation, increased apoptosis, and decreased invasion and migration in A549 cells. Moreover, we found that PDCD10 expression was increased in NSCLC tissues and cells. PDCD10 expression was positively correlated with tumor size and stage. Overexpression of PDCD10 increased cell proliferation and inhibited apoptosis in A549 cells. The data demonstrated that dysregulation of the miR-103/PDCD10 signal may be a novel therapeutic target for the treatment of NSCLC.

XPG genetic polymorphisms and clinical outcome of patients with advanced non-small cell lung cancer under platinum-based treatment: a meta-analysis of 12 studies

PURPOSE

A number of studies on the relationship between xeroderma pigmentosum group G (XPG) polymorphisms and clinical outcomes in non-small cell cancer (NSCLC) have led to inconclusive results. This meta-analysis evaluates the predictive value of XPG polymorphisms on the treatment response rate and overall survival of patients with NSCLC.

METHODS

To measure the correlative strength of the relationship between XPG polymorphisms and outcomes of patients with NSCLC, we searched electronic databases, including PubMed and China National Knowledge Infrastructure, to retrieve studies up to August 2016. We also employed pooled odds ratios (ORs) and hazard ratios (HRs) corresponding to 95% confidence intervals (95% CIs).

RESULTS

Twelve studies involving 2877 patients with NSCLC were included: 8 studies involving 1473 patients examined the correlation between XPG polymorphisms and tumor response rate and 7 studies involving 2329 patients reported on the correlation of XPG polymorphisms with overall survival. None of the XPG His1104Asp(C>G)/His46His(C>T) polymorphisms exhibited a correlation with treatment response rate or overall survival. However, in a further stratified analysis by ethnicity, carriers of the 1104G allele were associated with good response among Asians in the homozygote model (GG vs. CC: OR = 1.57, 95% CI: 1.05-2.34, P = 0.027). Meanwhile, further stratified by ethnicity, His46His polymorphism was not associated with RR and OS in any genetic models.

CONCLUSIONS

No strong evidence was found to support the use of XPG polymorphisms as tumor response and prognostic factors of patients with NSCLC receiving a platinum-based treatment regimen, which is attributed to marginal association. Studies with large-scale and multiple ethnicities need to be conducted to verify the conclusion.

Skin phenotypes can offer some insight about the association between telomere length and cancer susceptibility

The role of telomere biology in cancer has been studied for a wide variety of different cancers but the association with telomere length has been controversial. This is because some cancers have been found to be associated with longer telomeres in circulating white cells whilst other cancer types are more common in individuals with shorter telomeres. Hence, there has been some skepticism as to whether telomere length may be helpful in estimating cancer risk. For melanoma, however, results have been fairly consistent showing that longer telomeres are associated with an increased risk. This link was first discovered because of a link between longer telomeres and a high number of naevi. In contrast, for cutaneous squamous cell carcinomas, the relationship is reversed with higher risk in individuals with shorter telomeres. Differences in skin phenotypes with the presence of high number of naevi versus photoageing with solar elastosis and solar keratoses have already been valuable for dermatologists as the former phenotype is associated with melanoma whilst the latter is more common in patients with squamous cell carcinoma of the skin. The hypothesis is that the differences in cutaneous phenotypes already observed by dermatologists for skin cancers may, in fact, be useful as well for cancer prediction in general as it may reflect underlying telomere biology. This manuscript will address the evidence for links between telomere biology, skin phenotypes and cancer risk.

Lung cancer in chronic obstructive pulmonary disease patients, it is not just the cigarette smoke

PURPOSE OF REVIEW

An important association has been described between chronic obstructive pulmonary disease (COPD) and lung cancer, where different mechanisms have been proposed. There is no unique cause for this association, as COPD is by itself a heterogeneous disease, in which their classical phenotypes (i.e., emphysema and chronic bronchitis) each play an important role in lung cancer development. We will discuss recent evidence that links these two diseases and specific characteristics found in lung cancers from patients with COPD.

RECENT FINDINGS

Molecular studies have found specific gene expressions (reduction and overexpression) in lung tumors from patients with COPD, which likely predispose to increased methylation during lung carcinogenesis, and are associated with aggressiveness. Recent evidence suggests that lung cancer risk is higher in individuals with long telomeres, and that this effect takes place well in advance of diagnosis. Lung cancer is likely to develop in areas of the lung with greater emphysema and the severity of the latter is associated with larger and more aggressive tumors.

SUMMARY

Clinical and molecular studies have found that lung cancers that develop in patients with COPD and/or emphysema appear to be more aggressive and have a distinct molecular profile when compared with tumors from patients without an underlying lung disease. This could have important implications when deciding on personalized treatments.

Association Between Human Telomerase Reverse Transcriptase Gene Variations and Risk of Developing Breast Cancer

BACKGROUND

Despite a reduction in the number of deaths from cancers made possible by the development of early detection tests, improvements in treatment, changes in the age distribution of the population, and changes of personal behaviors as a result of awareness, breast cancer remains a major health problem worldwide. Breast cancer is the most common cancer and second leading cause of cancer death in women. Several genetic and environmental factors are known to be involved in breast cancer pathogenesis, but its exact etiology is complicated and is not clearly identified. The structure and integrity of telomeres are pivotal for genome stability, and telomere length is maintained by the expression of the telomerase enzyme. The human telomerase reverse transcriptase (hTERT) gene is a principal functional subunit of the telomerase. Several recent studies have provided evidence that hTERT gene variants may have an important role in cancer development.

METHODS

Three hTERT variants (rs2736100, rs2736098, and rs2853669) were genotyped for 107 breast cancer patients and 110 healthy controls to determine their effect on breast cancer susceptibility.

RESULTS

It was observed that hTERT rs2736098 was associated with breast cancer risk (odds ratio [OR] = 1.88; p = 0.034), while rs2736100 and rs2853669 did not significantly differ between the groups.

CONCLUSIONS

These findings are the first description of hTERT allele distributions in the Turkish population and may contribute to our understanding of breast cancer development. Nevertheless, further large-scale population studies are needed to understand the role of the hTERT polymorphisms and haplotypes in the development of breast cancer.