New study sheds light on tumor growth

The devil's advocate may know best in cancer research.

Contrary to scientific dogma, Penn researchers have found that certain proteins long thought to suppress tumor growth may actually facilitate it.

Complement proteins - a family of 30 proteins that are part of the immune system - had been thought to slow tumor growth, much in the same way they fight bacteria.

When researchers looked more closely at the mechanisms driving complement proteins, they found that these molecules may actually increase the rate of tumor growth.

Experiments so far have been carried out on a single tumor model in mice. Further tests need to be carried out on five other mouse models before results can be generalized, Maciej Markiewski, a School of Medicine researcher and the lead author of the study, said.

"By next year we will have an idea whether these models have more general applicability," John Lambris, the study's principal investigator, said.

Although this project is only in the initial stages, the new finding about complement proteins' function may open up new directions for cancer research.

On a medical level, complement inhibitors may change therapeutic techniques for cancer treatment.

Women who had cervical cancer from the human papilloma virus did not see improvements when treated with anti-tumor vaccines, Markiewski said.

These vaccines are not effective because tumors can suppress the immune system by way of the complement pathway, he explained. Complement inhibitors may help overcome this problem and make vaccines more effective.

Potential use of complement inhibitors in clinical settings is a very long-term prospective, he said.

Although the project controversially contests the long-standing notion that complement proteins are good, no major challenges surfaced with finding support or sufficient funding, Markiewski said.

The idea was so novel and the preliminary data strong that the National Institutes of Health supported the research, he added.

The NIH has contributed about $500,000 a year, Lambris said.

The study has received attention for its surprising findings and prospective health benefits.

"Researchers are noticing it because it sort of goes against what's expected, whereas clinicians may be interested in the therapeutic aspect," Robert DeAngelis, a Penn Med researcher and another study author, said.

It's too soon to tell the response in the scientific community, Markiewski added, noting that the original report was released only at the end of last month.

New technologies have advanced the field of cancer research, but work still remains.

"This is something like approaching a very complex computer chip with a hammer," Markiewski said.

More research is needed for scientists to fully understand tumor development, he added.

This article has been updated to reflect that John Lambris is the study's principal investigator. The original version said he was a researcher.

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