Cancer and Sirtuins: Activate or Supress??

There seems to be some conflicting ideas with regard to targeting sirtuins to fight cancer. Sirtris is researching how activation of sirtuins can stop cancer growth while others are looking to de-activate sirtuins to achieve the same result:

From Sirtris 2/20/08:

CAMBRIDGE, Mass., Feb 20, 2008 (BUSINESS WIRE) -- Sirtris Pharmaceuticals, Inc.
(NASDAQ: SIRT), a biopharmaceutical company focused on discovering and developing small molecule drugs to treat diseases of aging, announced that Sirtris co-founder David Sinclair, PhD, Harvard Medical School Associate Professor of Pathology, will present data showing that SIRT1 activation can suppress tumor formation and growth in the intestine and colon in a preclinical model of colon cancer. These are the first in-vivo data showing that SIRT1 overexpression can suppress tumor formation and growth. These data are the work of Sirtris Scientific Advisory board co-chairs Sinclair and Leonard Guarente, PhD, the Novartis Professor of Biology at the Massachusetts Institute of Technology

From Sirtris 2/21/08:

The National Cancer Institute will test the compounds in well-established cancer cell lines which were previously used in the development of novel and existing chemo-therapeutics. The cell lines to be tested include some of the most common cancer types. The program will also test Sirtris' compounds using in-vivo mouse tumor models to determine if the compounds reduce or limit the growth of the tumor cells. Previous studies have shown that calorie restriction--a method which has been shown to increase SIRT1 activation--can exert strong tumor suppressor effects in mammals and increase lifespan in organisms. Through direct activation of the SIRT1 enzyme with Sirtris' compounds, researchers in this study will be able explore the enzyme's role in tumor suppression along multiple pathways.

Exerpt from From University of Bath press announcement (undated, but recent):

"...Studies have shown that increased levels of these enzymes, known as sirtuins,
are found in tumours from a range of different cancer types.

This suggests that, by finding a way of preventing these enzymes from working, it may be possible to halt the progression of cancer by stopping tumour cells from
dividing and growing. "