MicroRNAs (miRNAs) are key epigenomic regulators of biological processes in animals and plants. These small non coding RNAs form a complex networks that regulate cellular function and development. MiRNAs prevent translation by either inactivation or inducing degradation of mRNA, a major concern in post-transcriptional gene regulation. Aberrant regulation of gene expression by miRNAs is frequently observed in cancer. Overexpression of various 'oncomiRs' and silencing of tumor suppressor miRNAs are associated with various types of human cancers, although overall downregulation of miRNA expression is reported as a hallmark of cancer. Modulations of the total pool of cellular miRNA by alteration in genetic and epigenetic factors associated with the biogenesis of miRNA machinery. It also depends on the availability of cellular miRNAs from its store in the organelles which affect tumor development and cancer progression. Here, we have dissected the roles and pathways of various miRNAs during normal cellular and molecular functions as well as during breast cancer progression. Recent research works and prevailing views implicate that there are two major types of miRNAs; (i) intracellular miRNAs and (ii) extracellular miRNAs. Concept, that the functions of intracellular miRNAs are driven by cellular organelles in mammalian cells. Extracellular miRNAs function in cell-cell communication in extracellular spaces and distance cells through circulation. A detailed understanding of organelle driven miRNA function and the precise role of extracellular miRNAs, pre- and post-therapeutic implications of miRNAs in this scenario would open several avenues for further understanding of miRNA function and can be better exploited for the treatment of breast cancers.

MicroRNAs (miRNAs) 是动植物生物过程的关键表观基因组调控因子。这些小的非编码 RNA 形成一个复杂的网络，调节细胞功能和发育。miRNA 通过失活或诱导 mRNA 降解来阻止翻译，这是转录后基因调控的主要问题。在癌症中经常观察到 miRNA 对基因表达的异常调节。各种“oncomiRs”的过度表达和肿瘤抑制 miRNAs 的沉默与各种类型的人类癌症有关，尽管 miRNA 表达的整体下调被报道为癌症的标志。通过改变与 miRNA 机制的生物发生相关的遗传和表观遗传因素来调节细胞 miRNA 的总库。它还取决于影响肿瘤发展和癌症进展的细胞器中储存的细胞 miRNA 的可用性。在这里，我们剖析了各种 miRNA 在正常细胞和分子功能以及乳腺癌进展过程中的作用和途径。最近的研究工作和主流观点暗示 miRNA 有两种主要类型；(i) 细胞内 miRNA 和 (ii) 细胞外 miRNA。概念，细胞内 miRNA 的功能是由哺乳动物细胞中的细胞器驱动的。细胞外 miRNA 在细胞外空间的细胞间通讯中发挥作用，并通过循环使细胞保持距离。详细了解细胞器驱动的 miRNA 功能和细胞外 miRNA 的确切作用，