By Merritt McKinney

NEW YORK, Mar 20 (Reuters Health) - A compound that blocks an enzyme involved in cell division holds promise as a tumor-shrinking treatment, researchers in Europe report.

There is no guarantee that the molecule itself, known as CINK4, will ever be used to treat cancer, but the research opens the door to a new approach for cancer therapy, one of the study's authors told Reuters Health.

CINK4 blocks an enzyme called Cdk4 that is involved in cell division. Cdk4 "represents a prime target for the treatment of cancer" because the pathway of the enzyme goes awry in most types of human tumors, according to Dr. Bhabatosh Chaudhuri, of De Montfort University in Leicester, UK, and colleagues at Novartis Pharma AG in Basel, Switzerland.

Many tumors, including some types of lung cancer, lack p16, a molecule in this pathway that keeps cells from dividing uncontrollably.

Chaudhuri's team identified CINK4 after screening a large number of potentially Cdk4-inhibiting molecules. After identifying CINK4, the researchers tested the molecule's ability to block Cdk4 in a series of laboratory tests.

Once they had confirmed CINK4's ability to inhibit Cdk4, the researchers tested its effects in mice that had been injected with human colon cancer cells. After nearly a month of treatment with CINK4 or "sham" injections, tumors shrank significantly more in mice treated with the molecule, according to a report in the March 21st issue of the Journal of the National Cancer Institute.

The findings are encouraging, but they do not necessarily mean that CINK4 itself will ever be used as a cancer treatment, according to Chaudhuri.

"Our findings have only proven the concept that inhibiting the activity of...Cdk4 with a small molecule can indeed be a promising way to treat cancer since Cdk4 activity is perturbed in most, if not all, cancers," Chaudhuri told Reuters Health.

He noted that CINK4 is not yet a therapy for cancer. "But similar molecules have the potential of becoming one," he added.

An editorial that accompanies the study urges caution in interpreting the findings.

"Ultimately, the challenge will be to rigorously confirm these, and other, preclinical findings and to prioritize the most promising agents for human clinical studies," write Drs. Akihito Kubo and Frederic J. Kaye, both of the National Institutes of Health.

But before placing too much hope in the search for agents that target key molecules involved in cancer, it is important to realize that the current understanding of how tumors grow is still incomplete, the editorialists note.

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