Lung cancer is the most frequently diagnosed cancer and the most common cause of cancer death globally, of which 85% is non-small cell lung cancer (NSCLC). revealed the levels of eight overexpressed miRNAs were similar between cellular and exosomal miRNAs and suggested circulating tumor exosomes as diagnostic biomarkers (32). This hypothesis is supported by some studies (33-35) but repudiated by other results (28,30). In spite of the contradictions of current findings, the use of circulating biomarkers as non-invasive cancer biomarkers is well established. miRNAs as biomarkers in NSCLC and the system To date, research possess demonstrated the part of miRNAs while biomarkers in NSCLC strongly. Overexpression of oncogenic SCH 530348 price miRNAs and reduced manifestation of tumor suppressive miRNAs could both become recognized SCH 530348 price in NSCLC. A few of them have already been verified to be engaged in the advancement or development of lung tumor, and the principal miRNAs GNAS are miR-21, miR-17-92 cluster SCH 530348 price and miR-221/222 as oncogenic miRNAs and let-7 family, miR-34 family and miR-200 family as tumor suppressive miRNAs (36). The let-7 family was the first discovered human-encoded miRNA, of which the expression was also shown reduced in NSCLC patients indicating poor prognosis (37,38). Let-7 possesses tumor suppressive activity, inhibiting multiple oncogenes such as (39), (40) and (41), and reduces the expression of cyclins (42). In lung cancer, chromosomal regions made up of various let-7 genes were reported often deleted (43). Moreover, a frequent SNP at the let-7 complementary site 6 was validated to have an association with an increased risk for NSCLC among smokers (44). The miR-34 family comprises miR-34a, miR-34b and miR-34c, acting as mediators of tumor suppression by P53 (45). All members of the miR-34 family are capable of repressing tumor growth and metastasis by targeting mRNAs participating in cell cycles, epithelial-mesenchymal transition (EMT), metastasis, stemness, apoptosis and senescence (46). It was observed that miR-34 genes were frequently downregulated by CpG methylation in various types of tumor or deleted as a minor cause (47). One study revealed that miR-34 synergistically with miR-15a/16 was significantly downregulated in NSCLC cell SCH 530348 price lines (48). Another study identified tissue miR-34a as an independent prognostic marker of recurrence in surgically resected NSCLC (49). Additionally, aberrant methylation of tissue miR-34 was indicated as a prognostic factor for NSCLC (50,51). All five members of the miR-200 family (miR-200a, miR-200b, miR-200c, miR-141 and miR-429) underwent remarkable downregulation in cells with EMT, which is regarded as a critical step in metastasis (52). EMT induced by the miRNAs was considered as a result of regulation of zinc finger E-box-binding homeobox (ZEB) transcription factors and E-cadherin (53). Loss of miR-200c expression was shown to give rise to an aggressive, invasive, and chemoresistant phenotype of NSCLC (54). However, other clinical outcomes contradict the above findings about miR-200c, as poor survival rates, not provided by previous studies, were exhibited in NSCLC with overexpression of miR-200c (55,56). The oncogenic property of miR-200c was argued by its potential to target several tumor suppressor genes as a more dominant role than regulation of ZEB in NSCLC carcinogenesis (56). MiR-21 is an oncogenic miRNA and overexpressed in multiple solid tumors (57), including NSCLC. MiR-21 promotes tumorigenesis through inhibition of regulators of the Ras/MEK/ERK pathway and blockage of apoptosis (58). Unfavorable regulation on tumor suppressive genes, such as (59), (60), (61) and (62) has been reported to be part of miR-21s SCH 530348 price oncogenic mechanism. The elevated expression of miR-21 was much higher in tumor tissues and cell lines with epidermal growth factor receptor (identified plasma miR-21 as a sensitive and specific marker for early diagnosis for NSCLC and a predicative indicator for response sensitivity.