Scientists at the University of California, San Diego have identified a previously¹ unknown kinase（激酶，致活酶） that regulates cell proliferation（增殖，扩散） , shape and migration², and may play a major role in the progression or metastasis（转移，新陈代谢） of cancer cells. The research will be published in the May 31 online Early Edition of the Proceedings³ of the National Academy of Sciences.

Richard L. Klemke, PhD, professor of pathology（病理学） at the UCSD School of Medicine and the Moores Cancer Center, and colleagues say the new kinase or enzyme⁴ regulates the cytoskeleton（细胞骨架） – the internal framework of tiny filaments⁵（花丝，灯丝） and microtubules in cells that gives them shape, coherence⁶ and the ability to move.

"This molecule⁷ may be an important new target for future anticancer therapies and a clinical biomarker that predicts whether a cancer is likely to spread," said Klemke.

Proper regulation of the cytoskeleton is important to many fundamental cellular⁸ functions, including axon/dendrite formation, migration, differentiation⁹ and proliferation. Conversely, deregulation of the cytoskeleton can contribute to a variety of human diseases, including cancer metastasis or the spread of tumors to other parts of the body.

The new kinase – called pseudopodium（虚足，假足） -enriched atypical kinase one or PEAK1 – plays a central role in the formation of cellular pseudopodia（伪足） . Greek for "false foot," a pseudopodium is a highly specialized¹¹ structure that protrudes¹² from the surface of migrating cells. It attaches the leading, extending membrane¹³ of the cell to its underlying¹⁴ substrate（基质，底片） , and then helps pull the cell forward. By endlessly repeating this process, a cell is able to move in a productive manner.

"Cancer cells capitalize on their innate¹⁵ ability to move in this fashion when they metastasize," said Jonathan A. Kelber, PhD, leading author on the paper and postdoctoral fellow in Klemke's lab. "Cancer cells detach from（分离，拆卸） the primary tumor¹⁰, invade the extracellular（细胞外的） milieu¹⁶（环境，周围） and then enter the vascular¹⁷ system（血管系统） from which they can spread and seed new tumors in distant tissues."

Discovering PEAK1 provides researchers with a new player to study and investigate, one that may have significant influence in the biology of cells, particularly cancer cells. Evidence from mouse studies suggests PEAK1 is an important player during tumor growth, and Klemke's team has further demonstrated that PEAK1 levels are increased in primary and metastatic samples from human colon¹⁸ cancer patients. Whether PEAK1 is capable of transforming non-tumor cells into cancer cells remains¹⁹ to be determined²⁰.

"One exciting fact is that PEAK1 has kinase activity, which suggests you can design a small molecule drug that would specifically inhibit²¹ its activity," said Kelber. "But that work lies in the future. First, we need to fully²² identify the role of its kinase domain²³ in tumor progression."