Protein Identified in Post-Chemo Cell Death Puzzle

Chemotherapy

Because anticancer drugs are designed to kill growing cells, they also affect normal, fast-growing cells—blood cells forming in the bone marrow, for example, and digestive, reproductive, and hair follicle cells. Chemotherapy may also affect cells in vital organs, such as the heart, kidney, bladder, lungs, and nervous system.

Researchers at the University of Rochester, collaborating with colleagues at MIT, Harvard, and the University of Oslo, have identified a protein that is required for cell death after undergoing chemotherapy—at least, it appears, in male mice.

“That was the unexpected part,” says Dragony Fu, an assistant professor of biology at Rochester and corresponding author of the study, regarding the sex-specific nature of the experimental results.

The researchers used mice that were engineered to lack a protein they suspected would otherwise cause normal cells to self-destruct after exposure to chemotherapy or other stresses—a “regulated” death aimed at heading off the risk of mutation. The protein, ALKBH7, is one of several proteins that can trigger cell death in both mice and humans.

In the study, published in Cell Death & Disease, the researchers show that healthy photoreceptor cells and cerebellar granule neuron cells were significantly more likely to survive chemotherapy in mice that had been genetically engineered to lack ALKBH7, as opposed to control mice that still had ALKBH7.

But surprisingly, the improvement in brain cell survival rates occurred only in male mice, and was far more pronounced in males for photoreceptor cells as well.

“We don’t know why that is,” Fu says. “But we have some potential leads.”

Chemotherapy
In a study published in Cell Death & Disease, University researchers show that when mice are genetically engineered to lack a protein known as ALKBH7 (at right), their photoreceptor cells and cerebellar granule neuron cells are significantly more likely to survive chemotherapy opposed to control mice that still have ALKBH7 (at left). But surprisingly, the improvement in brain cell survival rates occur only in male mice, and is far more pronounced in males for photoreceptor cells as well. (University of Rochester illustration / Michael Osadciw)

Fu suspects that additional genetic and molecular factors, including hormones and other cellular proteins, affect a cell’s response to chemotherapy. For example, the XY chromosome cells found in males have different mechanisms for triggering cell death than the XX chromosome cells found in females.

“So that brings up an intriguing point, that male and female cells die in different ways depending on what they are exposed to,” Fu says. “If you give a male and a female the same dose of chemotherapy, it could have completely different effects.”

Fu will continue to study the role of ALKBH7—now taking the possibility of sex-specific behaviors of the protein into account. Further research on ALKBH7 will help to determine:

  • Whether there are certain cancers that arise from ALKBH7 deficiency
  • And if so, are there ways to selectively re-introduce the ALKBH7 protein—or other proteins that trigger cell death—into cancer cells but not in the normal cells?

In addition, in a previous study, Fu found that cells lacking ALKBH7 have a greater number of mutations after chemotherapy compared to cells with ALKBH7. “Thus, we have to weigh the cost/benefit of increasing the survival rate of normal cells with the increased risk of mutation and cancer,” he says.

“By gaining a better understanding of how cells respond to chemotherapy, we are hoping to make these therapies more targeted for certain kinds of cells, such as a cancer cells—and also, importantly, to lessen the affects they have on our normal cells,” Fu says.

The study is a continuation of research Fu began prior to coming to Rochester, when he was an American Cancer Society postdoctoral fellow in the lab of study co-author Leona Samson, a professor of biological engineering at MIT. Samson is an expert in how cells respond to chemotherapy. While in Samson’s lab, Fu collaborated with lead author Jennifer Jordan, a postdoctoral fellow, on uncovering the role of ALKBH7 in triggering cell death after chemotherapy.

Source : University of Rochester