UCSF Scientists Illuminate How MicroRNAs Drive Tumor Progression

By Elizabeth Fernandez, UCSF News Office | September 16, 2009

UCSF researchers have identified collections of tiny molecules known as microRNAs that affect distinct processes critical for the progression of cancer. The findings, they say, expand researchers' understanding of the important regulatory function of microRNAs in tumor biology and point to new directions for future study and potential treatments.

The researchers refer to these microRNA collections as signatures, and their study results are reported in the September 15 issue of "Genes & Development.'' The study, available online at http://genesdev.cshlp.org/, was led by the laboratory of Douglas Hanahan, PhD, an American Cancer Society Research Professor in the Department of Biochemistry and Biophysics at UCSF.

Approximately five percent of all known human genes encode, or produce, microRNAs, yet scientists are only now - nearly a decade after their discovery -- beginning to unlock the mystery of their functions.

MicroRNAs are snippets of single-stranded RNAs that prevent a gene's code from being translated from messenger RNA into proteins, which are essential for cell growth and development. Produced in the nucleus and released into the cytoplasm, they home in on messenger RNAs that possess a stretch that is complementary to their genetic sequence. When they locate them, they latch on, preventing the messenger RNA from being processed by the protein-making machines known as ribosomes. As such, microRNAs are able to ratchet down a cell's production of a given protein.

Over the last several years, several groups have identified hundreds of microRNAs that are deregulated between normal tissue and tumors, however researchers only understand what a handful of these powerful regulators are doing to drive tumor formation.

"Virtually all cancers acquire approximately six distinct capabilities en route to tumor formation," said lead author Peter Olson, PhD, a postdoctoral fellow in the Diabetes Center and Helen Diller Family Comprehensive Cancer Center at UCSF. "When a cancer researcher observes a gene or microRNA go awry, it can be challenging to understand how that microRNA impacts tumorigenesis."


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