biostudies-literatureUnknown8(1)Chirshev ELoma Linda UniversityLoma Linda University, Division of AnatomyAbnormal 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 poteClinical and translational medicine24https://www.ebi.ac.uk/biostudies/studies/S-EPMC6715759biostudies-literatureLet-7 as biomarker, prognostic indicator, and therapy for precision medicine in cancer.PMC6715759Ioffe YJUnternaehrer JJChirshev EOberg KCfalseLet-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 pote2019-01-01T00:00:00Z2019 Aug2025-04-18T18:02:29.39Z2019-09-24T07:05:33ZS-EPMC67157593146825010.1186/s40169-019-0240-y