Association between genetic polymorphisms in the promoters of let-7 and risk of cervical squamous cell carcinoma

The microRNA Let-7 and its exosomal form: Epigenetic regulators of gynecological cancers

Many types of gynecological cancer (GC) are often silent until they reach an advanced stage, and are therefore often diagnosed too late for effective treatment. Hence, there is a real need for more efficient diagnosis and treatment for patients with GC. During recent years, researchers have increasingly studied the impact of microRNAs cancer development, leading to a number of applications in detection and treatment. MicroRNAs are a particular group of tiny RNA molecules that regulate regular gene expression by affecting the translation process. The downregulation of numerous miRNAs has been observed in human malignancies. Let-7 is an example of a miRNA that controls cellular processes as well as signaling cascades to affect post-transcriptional gene expression. Recent research supports the hypothesis that enhancing let-7 expression in those cancers where it is downregulated may be a potential treatment option. Exosomes are tiny vesicles that move through body fluids and can include components like miRNAs (including let-7) that are important for communication between cells. Studies proved that exosomes are able to enhance tumor growth, angiogenesis, chemoresistance, metastasis, and immune evasion, thus suggesting their importance in GC management.

A glimpse into let-7e roles in human disorders; friend or foe?

MicroRNAs (miRNAs) have been linked to abnormal expression and regulation in a number of diseases, including cancer. Recent studies have concentrated on miRNA Let-7e's significance in precision medicine for cancer screening and diagnosis as well as its prognostic and therapeutic potential. Differential let-7e levels in bodily fluids have the possibility to enable early detection of cancer utilizing less-invasive techniques, reducing biopsy-related risks. Although Let-7e miRNAs have been described as tumor suppressors, it is crucial to note that there exists proof to support their oncogenic activity in vitro and in in vivo. Let-7e's significance in chemo- and radiation treatment decisions has also been demonstrated. Let-7e can also prevent the synthesis of proinflammatory cytokines in a number of degenerative disorders, including musculoskeletal and neurological conditions. For the first time, an overview of the significance of let-7e in the prevention, detection, and therapy of cancer and other conditions has been given in the current review. Additionally, we focused on the specific molecular processes that underlie the actions of let-7e, more particularly, on malignant cells.

Dual mechanism of Let-7i in tumor progression

Let-7i regulates tumors primarily by binding to the 3' untranslated region (3' UTR) of mRNA, which indirectly regulates post-transcriptional gene expression. Let-7i also has an epigenetic function via modulating DNA methylation to directly regulate gene expression. Let-7i performs a dual role by inducing both the promotion and inhibition of various malignancies, depending on its target. The mechanism of Let-7i action involves cancer cell proliferation, migration, invasion, apoptosis, epithelial-mesenchymal transition, EV transmission, angiogenesis, autophagy, and drug resistance sensitization. Let-7i is closely related to cancer, and hence, is a potential biomarker for the diagnosis and prognosis of various cancers. Therapeutically, it can be used to promote an anti-cancer immune response by modifying exosomes, thus exerting a tumor-suppressive effect.

Melatonin targeting non-coding RNAs in cancer: Focus on mechanisms and potential therapeutic targets

Despite, melatonin is mainly known as a regulatory factor for circadian rhythm, its notable role in other fundamental biological processes, such as redox homeostasis and programmed cell death, has been found. In this line, a growing body of evidence indicated that melatonin could apply an inhibitory effect on the tumorigenic processes. Hence, melatonin might be considered an efficient adjuvant agent for cancer treatment. Besides, the physiological and pathological functions of non-coding RNAs (ncRNAs) in various disease, particularly cancers, have been expanded over the past two decades. It is well-established that ncRNAs can modulate the gene expression at various levels, thereby, ncRNAs. can regulate the numerous biological processes, including cell proliferation, cell metabolism, apoptosis, and cell cycle. Recently, targeting the ncRNAs expression provides a novel insight in the therapeutic approaches for cancer treatment. Moreover, accumulating investigations have revealed that melatonin could impact the expression of different ncRNAs in a multiple disorders, including cancer. Therefore, in the precent study, we discuss the potential roles of melatonin in modulating the expression of ncRNAs and the related molecular pathways in different types of cancer. Also, we highlighted its importance in therapeutic application and translational medicine in cancer treatment.

Genetic variants in the promoters of let-7 are associated with the risk and age at onset of ischemic stroke: A case control study

PURPOSE

Let-7 family members serve as crucial regulatory molecules in the pathogenesis of ischemic stroke. We predicted that genetic variations in the let-7 family's promoters may be linked to the risk of ischemic stroke. The connection of rs10877887 and rs13293512 in the let-7 family promoters with liability to ischemic stroke was explored in this study.

PATIENTS AND METHODS

Clinical data and peripheral blood samples were collected from 914 ischemic stroke patients and 836 controls in this case-control study. All statistical analyses were carried out using SPSS.

RESULTS

Our analysis results reveal that the rs10877887 TC+CC genotype in the dominant model is associated with a lower risk of ischemic stroke than the TT genotype. Individuals with heterozygous TC or homozygous CC genotypes in the male population showed higher odds of ischemic stroke than those with the wild TT genotype in rs13293512 analysis. Furthermore, there existed a multiplicative interaction between the rs10877887 C allele and the rs13293512 T allele. In the presence of the rs13293512 T allele, the effect of the rs10877887 C allele on ischemic stroke risk was increased. Similarly, in the presence of the rs10877887 C allele, the outcome of the rs13293512 T allele on ischemic stroke risk was elevated. In addition, the rs13293512 CC genotype seemed to lead to an earlier onset of ischemic stroke.

CONCLUSION

Our findings indicated that these two SNPs might have a joint role in IS and could potentially act as risk markers. Detecting let-7 promoter polymorphisms could raise awareness of the risk of IS, which directed individuals with risk alleles to have regular checks at an appropriate frequency to avoid developing the disease.

Relation of genetic polymorphisms in microRNAs with diastolic and systolic function in type 2 diabetes mellitus

BACKGROUND AND AIMS

Type 2 diabetes mellitus (T2DM) has high risk of developing cardiac dysfunction, increasing of either cardiovascular death or hospitalization for heart failure. MicroRNAs (miRNA) affect cardiac function of T2DM. The aim of this study was to investigate the relationships between five miRNA single nucleotide polymorphisms (SNP) and diastolic and systolic function of T2DM.

METHODS AND RESULTS

Three hundred untreated T2DM subjects were included. Each subject underwent SNP genotyping, conventional echocardiography, tissue doppler imaging, and speckle tracking imaging. The effects of miRNA SNPs on diastolic and systolic function were evaluated. The diastolic function of T2DM subjects with miR-133a-1-rs8089787 wild genotype or let-7f-rs10877887 variant genotype was lower than those with miR-133a-1-rs8089787 variant genotype or let-7f-rs10877887 wild genotype, manifesting as higher left atrial volume index, lower mean E', and higher E/E' (P < 0.05). There were no significant effects of miR-133a-2-rs13040413, let-7a-1-rs13293512 and miR-27a-rs895819 on the diastolic function of T2DM subjects (P > 0.05). These five miRNA SNPs had no effect on the systolic function of T2DM subjects (P > 0.05).

CONCLUSIONS

MiRNA-133a-1-rs8089787 and let-7f-rs10877887 were associated with impaired cardiac diastolic function in T2DM. The findings may be a promising therapeutic targets for preventing diastolic dysfunction in T2DM.

Let-7 as a Promising Target in Aging and Aging-Related Diseases: A Promise or a Pledge

The abnormal regulation and expression of microRNA (miRNA) are closely related to the aging process and the occurrence and development of aging-related diseases. Lethal-7 (let-7) was discovered in Caenorhabditis elegans (C. elegans) and plays an important role in development by regulating cell fate regulators. Accumulating evidence has shown that let-7 is elevated in aging tissues and participates in multiple pathways that regulate the aging process, including affecting tissue stem cell function, body metabolism, and various aging-related diseases (ARDs). Moreover, recent studies have found that let-7 plays an important role in the senescence of B cells, suggesting that let-7 may also participate in the aging process by regulating immune function. Therefore, these studies show the diversity and complexity of let-7 expression and regulatory functions during aging. In this review, we provide a detailed overview of let-7 expression regulation as well as its role in different tissue aging and aging-related diseases, which may provide new ideas for enriching the complex expression regulation mechanism and pathobiological function of let-7 in aging and related diseases and ultimately provide help for the development of new therapeutic strategies.

Melatonin promotes apoptosis of thyroid cancer cells via regulating the signaling of microRNA-21 (miR-21) and microRNA-30e (miR-30e)

Melatonin (MEL) is an effective therapeutic choice for thyroid cancer treatment. In this study, we aimed to explored the potential effect of MEL upon the drug sensitivity of cancer cells and the according underlying mechanisms. Thyroid cancer mice were established as a control group and a MEL group to observe the in vivo effect of MEL. Tumor size and weight in nude mice were detected to evaluate the effect of MEL on tumor growth. Immunohistochemistry assay (IHC) and Western blot were performed to analyze the expression of PTEN protein in tumor cells or tumor cells. After 32 days of cancer cell implantation, MEL was found to significantly repress tumor growth in nude mice approximately by half. Moreover, MEL also suppressed tumor cell proliferation, while apparently activating the apoptosis of tumor cells. In addition, hydrogen sulfide (H₂S) production was obviously elevated by MEL treatment. Mechanistically, the expression of phosphatase and tensin homolog (PTEN) was remarkably activated by MEL treatment in tumor tissues of implanted TPC-1 and BCPaP cells in nude mice. Meanwhile, MEL inhibited the expression of miR-21 and miR-30e and promoted the expression of lncRNA-cancer susceptibility candidate 7 (CASC7). Both miR-21 and miR-30e could suppress PTEN expression, while miR-21 could also inhibit the expression of lncRNA-CASC7. In conclusion, the results demonstrated that the MEL administration could downregulate the expression of miR-21 and miR-30e, which resulted in increased expression of PTEN, a pro-apoptotic tumor suppressor, to promote the apoptosis of thyroid cancer cells.

Cervical Cancer, Papillomavirus, and miRNA Dysfunction

Cervical cancer is the leading cause of death by cancer in women from developing countries. Persistent infection with high-risk human papillomavirus (HPV) types 16 and 18 is a major risk factor for cervical carcinogenesis. Nevertheless, only a few women with morphologic expression of HPV infection progress into invasive disease suggesting the involvement of other factors in cervical carcinogenesis. MicroRNAs (miRNAs) are conserved small non-coding RNAs that negatively regulate gene expression including genes involved in fundamental biological processes and human cancer. Dysregulation of miRNAs has been widely reported in cervical cancer. This work focuses on reviewing the miRNAs affected during the HPV infection process, as well relevant miRNAs that contribute to the development and maintenance of malignant cervical tumor cells. Finally, we recapitulate on miRNAs that may be used to distinguish between healthy individuals from patients with precancerous lesions or cervical tumors.

Genetic Variations in miR-30 Family Member Regulatory Regions Are Associated with Breast Cancer Risk in a Chinese Population

MicroRNAs (miRNAs) of the miR-30 family are closely linked with tumor metastasis and play key roles in the complex malignant phenotypes of cancers by targeting many tumor-related genes. Deregulated expression of miR-30 family members has been commonly observed in breast cancer. However, associations between the genetic variants in the regulatory region of miR-30 family and the risk of breast cancer are still limited, especially in the Chinese Han population. In the present study, we conducted a case-control analysis wherein 1064 breast cancer patients and 1073 healthy controls underwent genotyping of 10 SNPs in the regulatory region of miR-30 family members. Multivariate logistic regression analyses illustrated that the rs763354 variant in the miR-30a regulatory region was linked with a significant decrease in breast cancer risk in an additive model (adjusted OR = 0.86, 95% CI: 0.75-0.98, P = 0.022). Further, eQTL analyses also indicated that this SNP was associated with miR-30a expression levels in breast cancer samples compiled in the TCGA database (P = 0.020). The Kaplan-Meier plotter showed that breast cancer patients with higher miR-30a expression have significantly better outcomes than do patients expressing low levels of this miRNA (HR = 0.75, 95% CI: 0.61-0.91, P = 0.0041). Together, these findings suggest that the miR-30a rs763354 SNP is an important regulator of breast cancer risk, thus making it a potentially viable prognostic biomarker and one that can be used to guide therapeutic treatment in affected patients.

A Functional Polymorphism in the Promoter of miR-17-92 is Associated with a Reduced Risk of Cervical Squamous Cell Carcinoma

miR-17-92 cluster was differentially expressed in cervical cancer, playing an important role in regulating cell proliferation, apoptosis, migration, and invasion. The purpose of this study was to investigate the association between polymorphisms (i.e., rs9588884, rs982873, and rs1813389) in the promoter of miR-17-92 and the risk of cervical squamous cell carcinoma (CSCC). The rs9588884 polymorphism was genotyped using a Taqman assay and the rs982873 and rs1813389 polymorphisms were genotyped using a polymerase chain reaction-restriction fragment length polymorphism method. The expression levels of miR-17-92 were determined using a quantitative PCR analysis. The rs9588884 GG genotype was associated with a reduced risk of CSCC in homozygote comparison (adjusted OR = 0.47, 95% CI, 0.30-0.75, P = 0.001), dominant model (adjusted OR = 0.67, 95% CI, 0.50-0.91, P = 0.01), and recessive model (adjusted OR = 0.57, 95% CI, 0.38-0.85, P = 0.01). The rs9588884 G allele was also associated with a reduced risk of CSCC in allele comparison (adjusted OR = 0.71, 95% CI, 0.58-0.88, P = 0.002). Moreover, patients with the rs9588884 GG genotype had lower levels of miR-20a compared with the rs9588884 CC genotype (P = 0.03). These findings indicate that the rs9588884 GG genotype was associated with lower levels of miR-20a and eventually related to the risk of CSCC in Chinese women.

Association of Genetic Polymorphisms in MicroRNAs With Type 2 Diabetes Mellitus in a Chinese Population

INTRODUCTION

MicroRNAs (miRNA) involved in the insulin signaling pathways deeply affect the pathogenesis of T2DM. The aim of this study was to assess the association between single nucleotide polymorphisms (SNP) of the related miRNAs (let-7f rs10877887, let-7a-1 rs13293512, miR-133a-1 rs8089787, miR-133a-2 rs13040413, and miR-27a rs895819) and susceptibility to type 2 diabetes mellitus (T2DM), and its possible mechanisms.

METHODS

Five SNPs in miRNAs (let-7f rs10877887, let-7a-1 rs13293512, miR-133a-1 rs8089787, miR-133a-2 rs13040413, and miR-27a rs895819) involved in the insulin signaling pathways were selected and genotyped in a case-control study that enrolled 371 T2DM patients and 381 non-diabetic controls. The individual SNP association analyses, interaction analyses of SNP-SNP, SNP-environmental factors were performed. The effect the risk-associated polymorphism on regulating its mature miRNA expression was also evaluated.

RESULTS

In overall analyses, miR-133a-2 rs13040413 and let-7a-1 rs13293512 were related to the susceptibility to T2DM. In stratified analyses, miR-133a-2 rs13040413, let-7a-1 rs13293512 and miR-27a rs895819 showed associations with T2DM in the age ≥ 60 years subgroup. Moreover, let-7a-1 rs13293512 and miR-27a rs895819 showed associations with T2DM in male subgroup. In SNP-environmental factors interaction analyses, there were interaction effects of miR-133a-2 rs13040413 with dyslipidemia, let-7a-1 rs13293512 with smoking, and let-7a-1 rs13293512 with dyslipidemia on T2DM. In SNP-SNP interaction analyses, there were also interaction effects of miR-133a-1 rs8089787 with let-7a-1 rs13293512, and miR-133a-1 rs8089787 with let-7f rs10877887 on T2DM. Furthermore, for miR-133a-2 rs13040413, the variant T allele showed a trend toward decreased miR-133a expression in comparison with the wild C allele. For let-7a-1 rs13293512, the variant C allele expressed a lower let-7a compared to the wild T allele.

CONCLUSION

MiRNAs polymorphisms involved in the insulin signaling pathways and the interaction effects of SNP-SNP, SNP-environmental factors were related to T2DM susceptibility in a Chinese population.

Long Noncoding RNA HULC Promoter Polymorphism rs1041279 Is Associated with an Increased Risk of Cervical Squamous Cell Carcinoma

Hepatocellular carcinoma upregulated long noncoding RNA (HULC), identified as an oncogene in cervical cancer, is involved in not only the clinical stage, lymph node metastasis, and depth of cervical invasion but also outcome. In this study, we aimed to investigate the association between 3 polymorphisms (i.e., rs1041279, rs3005167, and rs7770772) in the promoter of HULC and the risk of cervical squamous cell carcinoma (CSCC). The polymorphisms were genotyped using the multiplex ligase detection reaction assay. The promoter activity was measured using the dual-luciferase reporter assay kit. The rs1041279 GG genotype and G allele revealed a significantly higher risk of CSCC compared with the rs1041279 CC genotype and C allele (GG vs. CC, adjusted OR = 1.79, 95% CI, 1.17-2.73, P = 0.007; G vs. C, adjusted OR = 1.36, 95% CI, 1.09-1.69, P = 0.006). Haplotype analysis revealed that the rs3005167C-rs7770772G-rs1041279C or rs3005167C-rs7770772G-rs1041279G haplotype had a significantly higher risk of CSCC compared to the rs3005167G-rs7770772G-rs1041279C haplotype (CGC vs. GGC, OR = 2.38, 95% CI, 1.53-3.75, P < 0.001; CGG vs. GGC, OR = 3.76, 95% CI, 2.12-6.68, P < 0.001). Dual-luciferase reporter assay showed that the rs1041279 G promoter resulted in higher transcriptional activity compared with the rs1041279 C (P < 0.01). Additionally, the rs1041279 GG genotype carriers had an increased level of HULC expression (P = 0.03). These findings suggest that the HULC rs1041279 may be a useful marker for the etiology of CSCC.

Identification and performance evaluation of housekeeping genes for microRNA expression normalization by reverse transcription-quantitative PCR using liquid-based cervical cytology samples

Screening for cervical cancer by cytology has been effective in reducing the worldwide incidence and mortality rates of this disease. However, a number of studies have demonstrated that the sensitivity of conventional cervical cytology may be too low for detection of cervical intraepithelial neoplasias (CIN). Therefore, it is important to incorporate more sensitive molecular diagnostic tests that could substantially improve the detection rates and accuracy for identifying CIN lesions. MicroRNAs (miRNAs) are a class of small non-coding RNAs with the potential to provide robust non-invasive cancer biomarkers for detecting CIN lesions in liquid-based cervical cytology (LBC) samples. At present, there is no consensus on which are the best housekeeping genes for miRNA normalization in LBC. The present study aimed to identify housekeeping genes with consistent and reproducible performance for normalization of reverse transcription-quantitative PCR (RT-qPCR) expression analysis of miRNA using LBC samples. The present study firstly selected six potential candidate housekeeping genes based on a systematic literature evaluation. Subsequently, the expression levels of microRNAs U6, RNU-44, RNU-47, RNU-48, RNU-49 and hsa-miR-16 were measured in 40 LBC samples using RT-qPCR. The stability of each potential housekeeping gene was assessed using the NormFinder algorithm. The results revealed that U6 and RNU-49 were the most stable genes among all candidates requiring fewer amplification cycles and smaller variation across the sample set. However, RNU-44, RNU-47, RNU-48 and hsa-miR-16 stability exceeded the recommended housekeeping value suitable for normalization. The findings revealed that U6 may be a reliable housekeeping gene for normalization of miRNA RT-qPCR expression analysis using LBC samples.

Let-7 as biomarker, prognostic indicator, and therapy for precision medicine in cancer

Abnormal regulation and expression of microRNAs (miRNAs) has been documented in various diseases including cancer. The miRNA let-7 (MIRLET7) family controls developmental timing and differentiation. Let-7 loss contributes to carcinogenesis via an increase in its target oncogenes and stemness factors. Let-7 targets include genes regulating the cell cycle, cell signaling, and maintenance of differentiation. It is categorized as a tumor suppressor because it reduces cancer aggressiveness, chemoresistance, and radioresistance. However, in rare situations let-7 acts as an oncogene, increasing cancer migration, invasion, chemoresistance, and expression of genes associated with progression and metastasis. Here, we review let-7 function as tumor suppressor and oncogene, considering let-7 as a potential diagnostic and prognostic marker, and a therapeutic target for cancer treatment. We explain the complex regulation and function of different let-7 family members, pointing to abnormal processes involved in carcinogenesis. Let-7 is a promising option to complement conventional cancer therapy, but requires a tumor specific delivery method to avoid toxicity. While let-7 therapy is not yet established, we make the case that assessing its tumor presence is crucial when choosing therapy. Clinical data demonstrate that let-7 can be used as a biomarker for rational precision medicine decisions, resulting in improved patient survival.

Reference MicroRNAs for RT-qPCR Assays in Cervical Cancer Patients and Their Application to Studies of HPV16 and Hypoxia Biomarkers

MicroRNA (miRNA) expressions in tumor biopsies have shown potential as biomarkers in cervical cancer, but suitable reference RNAs for normalization of reverse transcription quantitative polymerase chain reaction (RT-qPCR) assays in patient cohorts with different clinicopathological characteristics are not available. We aimed to identify the optimal reference miRNAs and apply these to investigate the potential of miR-9-5p as human papilloma virus (HPV) 16 biomarker and miR-210-3p as hypoxia biomarker in cervical cancer. Candidate reference miRNAs were preselected in sequencing data of 90 patients and ranked in a stability analysis by RefFinder. A selection of the most stable miRNAs was evaluated by geNorm and NormFinder analyses of RT-qPCR data of 29 patients. U6 small nuclear RNA (RNU6) was also included in the evaluation. MiR-9-5p and miR-210-3p expression was assessed by RT-qPCR in 45 and 65 patients, respectively. Nine candidates were preselected in the sequencing data after excluding those associated with clinical markers, HPV type, hypoxia status, suboptimal expression levels, and low stability. In RT-qPCR assays, the combination of miR-151-5p, miR-152-3p, and miR-423-3p was identified as the most stable normalization factor across clinical markers, HPV type, and hypoxia status. RNU6 showed poor stability. By applying the optimal reference miRNAs, higher miR-9-5p expression in HPV16- than HPV18-positive tumors and higher miR-210-3p expression in more hypoxic than less hypoxic tumors were found in accordance with the sequencing data. MiR-210-3p was associated with poor outcome by both sequencing and RT-qPCR assays. In conclusion, miR-151-5p, miR-152-3p, and miR-423-3p are suitable reference miRNAs in cervical cancer. MiR-9-5p and miR-210-3p are promising HPV16 and hypoxia biomarkers, respectively.

MiRNA Polymorphisms and Cancer Prognosis: A Systematic Review and Meta-Analysis

Background: Accumulating studies have focused on the relationship between miRNAs polymorphisms and cancer prognosis. However, the results are conflicting and unconvincing. This systematic review and meta-analysis was conducted to explore the relationship between miRNAs polymorphisms and cancer prognosis, aiming to seek for markers with cancer prognostic function.

Methods: Hazard ratio of overall survival, disease-free survival (DFS) and recurrence-free survival were calculated to evaluate the association between miRNAs polymorphisms and cancer prognosis by using Stata software 11.0.

Results: We systematically reviewed the association of 17 miRNAs SNPs with cancer prognosis including 24,721 samples. It was shown that 6 miRNAs SNPs (miR-608 rs4919510, miR-492 rs2289030, miR-378 rs1076064, miR-499 rs4919510, miR-149 rs2292832, miR-196a2 rs11614913) were associated with better cancer overall survival (OS) while let-7i rs10877887 was associated with poor OS; the homozygous and heterozygote genotype of miR-423 were related to poor cancer relapse-free survival (RFS) when compared with the wild genotype; miR-146 rs2910164 was linked to favorable cancer DFS while miR-196a2 rs11614913 was associated with poor DFS.

Conclusions: In summary, let-7i rs10877887, miR-608 rs4919510, miR-492 rs2289030, miR-378 rs1076064, miR-423 rs6505162, miR-499 rs4919510, miR-149 rs2292832, miR-146 rs2910164, and miR-196a2 rs11614913 might serve as potential biomarkers for cancer prognosis.

A comprehensive evaluation for polymorphisms in let-7 family in cancer risk and prognosis: a system review and meta-analysis

miRNA polymorphisms had potential to be biomarkers for cancer susceptibility and prognosis. The mature miRNA-let-7 family was considered as the most important miRNA for the cancer incidence and progression. Recently, the promising let-7 miRNAs were reported to be associated with various cancers, but the results were inconsistent. We performed a first-reported systematic review with a meta-analysis for the association of let-7 family single nucleotide polymorphisms (SNPs) with cancer risk/prognosis. Ten studies were included with a total of 3878 cancer cases and 4725 controls for the risk study and 1665 cancer patients for the prognosis study in this meta-analysis. In the risk study, the let-7i rs10877887 and let-7a-1/let-7f-1/let-7d rs13293512 were shown no significant association for the overall cancer risk. In the stratified analysis, the rs10877887 variant genotype was significantly associated with a decreased cancer risk in head and neck cancer (TC compared with TT: P=0.017; odds ratio (OR) = 0.81; TC + CC compared with TT: P=0.020; OR = 0.82). In the prognosis study, the let-7i rs10877887 SNP was shown to be associated with a higher risk for cancer prognosis in the dominate model (P=0.004; hazard ratio (HR) = 1.32). The other two SNPs (let-7a-1 rs10739971 and let-7a-2 rs629367) were not found to be associated with cancer survival. None of the let-7 family polymorphisms had potential to be biomarkers for cancer susceptibility but let-7i rs10877887 SNP had potential to be predicting markers for cancer prognosis. In the future, large-sample studies are still needed to verify our findings.