The advent of Next Generation Sequencing technologies brought with it the discovery of several microRNA (miRNA) variants of heterogeneous lengths and/or sequences. Initially ascribed to sequencing errors/artifacts, these isoforms, named isomiRs, are now considered non-canonical variants that originate from physiological processes affecting the canonical miRNA biogenesis. To date, accurate IsomiRs abundance, biological activity, and functions are not completely understood; however, the study of isomiR biology is an area of great interest due to their high frequency in the human miRNome, their putative functions in cooperating with the canonical miRNAs, and potential for exhibiting novel functional roles. The discovery of isomiRs highlighted the complexity of the small RNA transcriptional landscape in several diseases, including cancer. In this field, the study of isomiRs could provide further insights into the miRNA biology and its implication in oncogenesis, possibly providing putative new cancer diagnostic, prognostic, and predictive biomarkers as well. In this review, a comprehensive overview of the state of research on isomiRs in different cancer types, including the most common tumors such as breast cancer, colorectal cancer, melanoma, and prostate cancer, as well as in the less frequent tumors, as for example brain tumors and hematological malignancies, will be summarized and discussed.

中文翻译：

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isomiRs 在癌症中的新兴作用：现有技术和最新进展

下一代测序技术的出现带来了一些异质长度和/或序列的 microRNA (miRNA) 变体的发现。最初归因于测序错误/伪影，这些名为 isomiRs 的异构体现在被认为是源自影响规范 miRNA 生物发生的生理过程的非规范变体。迄今为止，尚未完全了解准确的 IsomiRs 丰度、生物活性和功能；然而，isomiR 生物学的研究是一个非常有趣的领域，因为它们在人类 miRNome 中的频率很高，它们与典型 miRNA 合作的假定功能，以及表现出新功能作用的潜力。isomiRs的发现突出了包括癌症在内的多种疾病中小RNA转录环境的复杂性。在这一领域，isomiRs 的研究可以进一步深入了解 miRNA 生物学及其在肿瘤发生中的意义，也可能提供推定的新癌症诊断、预后和预测性生物标志物。在这篇综述中，全面概述了 isomiR 在不同癌症类型中的研究状况，包括最常见的肿瘤，如乳腺癌、结直肠癌、黑色素瘤和前列腺癌，以及不太常见的肿瘤，例如将总结和讨论脑肿瘤和血液系统恶性肿瘤。