MicroRNAs (miRNAs) are critical regulators of gene expression, and their dysregulation is closely linked to cancer. Amplification of oncomiRs or loss of tumor suppressor miRNAs can drive tumorigenesis. Genetic and epigenetic alterations in miRNA biogenesis machinery can lead to global miRNA depletion, which is oncogenic. Recent studies highlight the importance of miRNA dysregulation in cancer, with miRNAs playing key roles in cancer initiation, progression, and metastasis. miRNAs repress gene expression by binding to complementary sequences in the 3′ untranslated region (3′ UTR) of mRNAs, leading to degradation and preventing translation. miRNA biogenesis involves transcription of primary miRNAs (pri-miRNAs), processing by the Microprocessor complex (DROSHA and DGCR8), export to the cytoplasm by XPO5, and further processing by DICER1 to generate mature miRNAs. These miRNAs are then incorporated into the miRNA-induced silencing complex (miRISC) to target mRNAs for degradation. Dysregulation of miRNA biogenesis pathways is a common feature in cancer, with mutations in DROSHA, DGCR8, and DICER1 being associated with various cancers. For example, DROSHA mutations in Wilms tumor lead to reduced miRNA expression and poor prognosis. Similarly, DICER1 mutations are linked to pleuropulmonary blastoma and other cancers. These mutations affect miRNA processing and contribute to cancer progression. Additionally, epigenetic modifications such as DNA methylation and histone modifications can silence miRNA expression, promoting tumorigenesis. The miRNA biogenesis pathway is also regulated by other factors, including RNA-binding proteins and cell signaling pathways. For instance, the Hippo pathway controls miRNA biogenesis by regulating cell proliferation and differentiation. Stress responses, such as hypoxia, can also affect miRNA expression and function. The LIN28 family of proteins blocks let-7 miRNA biogenesis, promoting tumorigenesis. Overall, miRNA dysregulation is a critical aspect of cancer biology, with miRNA biogenesis pathways playing a central role in cancer development and progression. Understanding these pathways provides insights into potential therapeutic targets for cancer treatment.MicroRNAs (miRNAs) are critical regulators of gene expression, and their dysregulation is closely linked to cancer. Amplification of oncomiRs or loss of tumor suppressor miRNAs can drive tumorigenesis. Genetic and epigenetic alterations in miRNA biogenesis machinery can lead to global miRNA depletion, which is oncogenic. Recent studies highlight the importance of miRNA dysregulation in cancer, with miRNAs playing key roles in cancer initiation, progression, and metastasis. miRNAs repress gene expression by binding to complementary sequences in the 3′ untranslated region (3′ UTR) of mRNAs, leading to degradation and preventing translation. miRNA biogenesis involves transcription of primary miRNAs (pri-miRNAs), processing by the Microprocessor complex (DROSHA and DGCR8), export to the cytoplasm by XPO5, and further processing by DICER1 to generate mature miRNAs. These miRNAs are then incorporated into the miRNA-induced silencing complex (miRISC) to target mRNAs for degradation. Dysregulation of miRNA biogenesis pathways is a common feature in cancer, with mutations in DROSHA, DGCR8, and DICER1 being associated with various cancers. For example, DROSHA mutations in Wilms tumor lead to reduced miRNA expression and poor prognosis. Similarly, DICER1 mutations are linked to pleuropulmonary blastoma and other cancers. These mutations affect miRNA processing and contribute to cancer progression. Additionally, epigenetic modifications such as DNA methylation and histone modifications can silence miRNA expression, promoting tumorigenesis. The miRNA biogenesis pathway is also regulated by other factors, including RNA-binding proteins and cell signaling pathways. For instance, the Hippo pathway controls miRNA biogenesis by regulating cell proliferation and differentiation. Stress responses, such as hypoxia, can also affect miRNA expression and function. The LIN28 family of proteins blocks let-7 miRNA biogenesis, promoting tumorigenesis. Overall, miRNA dysregulation is a critical aspect of cancer biology, with miRNA biogenesis pathways playing a central role in cancer development and progression. Understanding these pathways provides insights into potential therapeutic targets for cancer treatment.