June 7, 2011

Tumors Spread Easily During Pregnancy

(Ivanhoe Newswire) --Cancer typically doesn't kill someone as a result of the initial tumor but as a result of tumors at distant sites that are derived from the initial tumor. Pregnancy appears to be permissive for tumor metastasis. Breast tumors that arise during pregnancy tend to spread earlier to distant sites. This study has uncovered a possible reason for this.

Ivan Stamenkovic, at the University of Lausanne, Switzerland and colleagues found that the increased metastasis from tumors of several different types that they observed in pregnant mice was a result of decreased activity of immune cells known as NK cells.

In addition, at least part of the inhibitory effect on NK cells was mediated by another group of immune cells, myeloid-derived suppressor cells. Consistent with this, the gene expression profile of the lungs of pregnant mice (a site to which many of the tumors metastasized) was reflective of myeloid-derived suppressor cell accumulation.

Of clinical interest, the majority of genes downregulated in the lungs of pregnant mice were also expressed at lower levels in samples from lung cancer patients with poor prognosis than in samples from patients with better prognosis. The authors therefore suggest that myeloid-derived suppressor cells may represent a shared mechanism of immune suppression during pregnancy and tumor growth.

SOURCE:  Journal of Clinical Investigation, published online June 6, 2011