Source: Vanessa deGier, UCSF News Services
September 30, 2007
Specific Immune Cells Play an Essential Role in Tumor Growth
UCSF researchers have discovered that blocking the function of a certain type of immune cell halts pancreatic islet tumor growth in mice. The finding proves, they say, that specific immune cells can play a critical role in the formation and subsequent growth of cancer.
The immune cell in question, the mast cell, plays a key role in inflammation by releasing histamine and other chemicals in the body. More commonly associated with asthma, eczema and allergy, mast cells also appear at the edges of invasive tumors in numerous types of cancer in humans. The researchers discovered that the accumulation of mast cells is required for blood vessel formation (angiogenesis) in tumors in mice. Blocking mast cell function completely shut down the ability of the tumor to commandeer the nutrients it needs for growth.
The researchers discovered this by administering a common anti-asthma/anti-allergy medication, cromolyn, at the site of the tumor. The medication triggered tumor shrinkage and regression in mice with pre-existing pancreatic islet tumors.
Cromolyn is currently designed to be delivered topically or by inhalation and is not optimized for whole body delivery in humans. However, the researchers stress that now that the importance of mast cells has been demonstrated, new mast cell-blocking drugs like cromolyn could be specifically designed for appropriate systemic delivery.
The study results will be reported on September 30th in an advance online publication by the journal Nature Medicine. The journal will also publish the findings in an upcoming print edition.
"This study provides a potential new target for stopping cancer progression that scientists and drug makers should further explore," said Gerard Evan, PhD, the Gerson and Barbara Bass Baker Distinguished Professor of Cancer Biology at UCSF, and co-leader of the Cell Cycling and Signaling Program at the UCSF Comprehensive Cancer Center. "In addition, a new design of cromolyn administration should be useful in stopping the expansion of pancreatic and other cancers in humans."
An association between inflammation and cancer has long been recognized, though it remains unclear to what extent inflammation is a cause or consequence of tumor growth. Recently, it has become clear, says Evan, that some oncogenes (a class of genes that stimulate normal cell growth but when mutated drive cancer) may be responsible for inducing inflammation at the tumor site.
(Note that in November 2007 the UCSF Comprehensive Cancer Center was renamed the UCSF Helen Diller Family Comprehensive Cancer Center.)
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