Molecule critical to healing wounds identified

Nov. 15, 2013 — Skin provides a first line of defense against viruses, bacteria and parasites that might otherwise make people ill. When an injury breaks that barrier, a systematic chain of molecular signaling launches to close the wound and re-establish the skin's layer of protection.

A study led by researchers from the University of Pennsylvania's School of Dental Medicine and published in the Journal of Cell Biology now offers a clearer explanation of the role of one of the players in the wound-healing process, a molecule called FOX01. Contrary to what had been expected, FOX01 is critical to wound healing, providing researchers with a possible new target for drugs that could help speed that process for people with impaired wound healing.

Senior author Dana Graves is a professor in Penn Dental Medicine's Department of Periodontics and is vice dean for scholarship and research. He collaborated on the study with Penn's Bhaskar Ponugoti, Fanxing Xu, Chenying Zhang, Chen Tian and Sandra Pacio.

A critical element of wound healing involves the movement of keratinocytes, the primary cells comprising the epidermis, or the outer layer of skin. Previous research had found that FOX01 was expressed at higher levels in wounds, but scientists did not understand what role the molecule was playing. In other scenarios, such as in cancer cells, FOX01 promotes cell death and interferes with the cell reproduction, two actions that would seem to be detrimental to healing.

To investigate the role of FOX01 in wound healing, Graves and colleagues bred mice that lacked the protein in their keratinocytes and then observed the wound healing process in these mice compared to mice with normal FOX01.

"We thought that deleting FOX01 would speed up the wound-healing process," Graves said, "but in fact it had the opposite effect."

The mice that lacked FOX01 showed significant delays in healing. Whereas all wounds on control mice were healed after one week, all of the experimental mice still had open wounds.

Digging deeper into this counterintuitive finding, the researchers examined the effect of reducing FOX01 levels on other genes known to play a role in cell migration. They found that many of these genes were significantly reduced, notably TGF-β1, a critical growth factor in wound repair. When the team added TGF-β1 to cells lacking FOX01, the cells behaved normally and produced the proper suite of molecules needed for healing, indicating that FOX01 acts upstream of TGF-β1 in the signaling pathway triggered during the healing process.

Further experimenting revealed that mice lacking FOX01 had evidence of increased oxidative stress, which is detrimental to wound healing.

"The wound healing environment is a stressful environment for the cell," Graves said. "It appears that upregulation of FOX01 helps protect the cell against oxidative stress."

The fact that FOX01 behaves in this unexpected way could have to do with the specialized microenvironment of a cell in a wound, Graves noted. While FOX01 does indeed promote cell death when it is highly activated, it does the opposite when moderately activated. Which activity it promotes depends on the environment in which it is acting.

Taken together, the study's findings demonstrate that FOX01 plays an integral role in two key processes in wound healing: activation of TGF-β1 and protecting the cell against oxidative damage. Its involvement in these aspects of healing make it a potential target for pharmaceuticals that could help speed healing.

"If you had a small molecule that increased FOX01 expression, you might be able to upregulate TGF-β1 as well as protect against the oxidative stress associated with wound healing," Graves said.

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MicroRNA molecule found to be potent tumor-suppressor in lung cancer

Sep. 16, 2013 — New research shows that microRNA-486 is a potent tumor-suppressor molecule in lung cancer, and that the it helps regulate the proliferation and migration of lung-cancer cells, and the induction of programmed cell death, or apoptosis, in those cells.

The preclinical study was led by researchers at the Ohio State University Comprehensive Cancer Center -- Arthur G. James Cancer Hospital and Richard J. Solove Research Institute (OSUCCC -- James). It found that microRNA-486 (miR-486) directly targets the insulin growth-factor pathway, which is important for cell survival and proliferation. Alternations in the pathway are believed to play an early role in tumor initiation and progression.

The researchers further found that miR-486 is itself regulated by the tumor-suppressor gene p53, the most frequently altered gene in human cancers, and that activity of miR-486 is partially dependent upon functional p53.

Published in the Proceedings of the National Academy of Sciences, the study suggests that miR-486 might serve as a biomarker for lung-cancer patients who might respond to treatment with insulin-growth-factor inhibitors.

"It wasn't known whether miR-486 functioned as an oncogene or a tumor-suppressor gene in lung cancer," says co-corresponding author Patrick Nana-Sinkam, MD, associate professor of medicine and a researcher with the OSUCCC -- James Molecular Biology and Cancer Genetics Program.

"miR-486 appears to be a biomarker for lung cancer, but its mechanisms of action remain unclear," he says. "These findings show that miR-486 serves a tumor-suppressor function in lung cancer, and that miR-486 action is partially dependent on p53."

"This partial reliance of one tumor-suppressor on another was a surprise," says principal investigator and co-corresponding author Carlo M. Croce, MD, director of Ohio State's Human Cancer Genetics program and the John W. Wolfe Chair in Human Cancer Genetics at the OSUCCC -- James. "We don't know yet what implications, if any, this might have for the development of targeted therapies."

MicroRNAs are a class of short, non-coding RNAs that regulate the translation or degradation of messenger RNA and therefore the proteins that cells make. Research is showing that certain microRNAs are frequently dysregulated in cancer.

Nana-Sinkam and his colleagues examined lung-tumor samples from 81 patients with stage-1 nonsmall-cell lung cancer and tumor-cell lines. Analyses identified miR-486 as the most decreased of microRNAs in the cells, so the researchers chose it for further investigation.

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