Aspirin may prevent colon cancer from spreading

AMSTERDAM -- The mighty aspirin has long been shown to increase survival in people with colorectal cancer, but how it provides that protection has baffled scientists, who want to understand how these things works so they might develop new and possibly better drugs.

In a Dutch study presented at the European Cancer Congress this week, researchers examined data from 999 colon cancer patients whose medical records showed they had been regular users of aspirin and had survived colon cancer. Specifically they were looking at differences in three proteins among tissue samples taken from the patients. The proteins were HLA-1, COX-2 and PIK3CA.

HLA proteins are the “ID” badges that tell the immune system which cells belong to the body and which are foreign. COX-2 is an enzyme that is produced in inflammatory responses, and PIK3CA is a gene that is mutated in many cancers.

They found a couple of interesting things. First people whose colon tumors produced HLA-1 and who took low doses of aspirin had 47 percent better survival. On the other hand, aspirin use did not correlate with survival in tumors showing high levels of either COX-2 or PI3KA. Just as importantly, patients whose tumors did not produce HLA-1 protein gained no added survival benefit from aspirin therapy.

They concluded that aspirin’s protective effect is related to platelet action in colon cancer. Platelets are the blood cells that clump together to form clots to prevent bleeding. Aspirin tends to interfere with that clumping action. Researchers think HLA-1 positive colon cancer cells may use platelets in some way to travel or metastasize to other parts of the body. It may be that aspirin disrupts that ability of tumor cells to interact with platelets and thereby reduces metastatic cancer.

In most cancers, once metastasis occurs the cancer becomes incurable. The implication of this study, if proven correct, is that metastasis may occur, in part, by way of the tumor’s ability to figuratively use “fake ID” to elude the body’s immune system, and aspirin may be able to show us how to block that and perhaps one day prevent cancers from traveling to distant parts of the body.