The University of Texas MD Anderson Cancer Center researchers have discovered a small piece of RNA can prevent prostate cancer from spreading by suppressing a common protein in prostate cancer stem cells.

The finding profiled a microRNA expression pattern in prostate cancer stem cells and established a rationale for developing the microRNA miR-34a, in essence creating a new way to treat prostate cancer.

MicroRNAs, short and single-stranded pieces of RNA, control the messenger RNA to make new proteins.

Professor Tang of MD Anderson’s Department of Molecular Carcinogenesis, says cancer stem cells can renew themselves, improve tumor-initiating ability, and resist treatment better than other cancer cells.

Cancer stem cells are linked to the tumor recurrence and spreading to other organs. Scientists think a surface protein called CD44 may help to grow the cells’ transferring ability.

CD44, expressed by cancer stem cells, has been associated with the development of tumor, so it was a direct and functional target of miR-34a, Tang said.

By suppressing CD44, miR-34a can inhibit prostate cancer stem cells during a series of experiments with cell lines, human xenograft tumors in mice and primary human prostate cancer samples.

MiR-34a decreased sharply in the prostate cancer cells which have large amounts of CD44 on the surface, but expressed at 25 to 70 percent of levels in 18 human prostate tumors where CD44 was not found.

Treatment with miR-34a helped cut CD44-positive tumor incidence. The study noted that tumor formed in all 10 animals were blocked from regenerating by treatment with miRNAS.

Other features of cancer stem cells include formation of self-renew, duplicating ability, and formations of spheres - also suppressed by miR-34a.

Significantly, when treating the mice with tumor, mirR-34a reduced the burden by half in one tumor type and abated the lung metastases in another type. It increased the survival rates.

However, the scientists also found an interesting relation between miR-34a and CD44. For example, when treated with microRNA, the CD44 protein and cancer cells related to it in tumors were reduced, but tumors with miR-34a blocked had more CD44 protein and messenger RNA.

Treating tumors with miR-34a has the same effect as with a short hairpin RNA.

Stephen Lau and editing by Aimee Keenan-Greene