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Gene therapy reported to wipe out pancreatic cancer in mice

July 9, 2007
Courtesy University of Texas M. D. Anderson Cancer Center
and World Science staff

A newly en­gi­neered ther­a­py, which em­beds a gene in pan­cre­at­ic can­cer cells, shrinks or erad­i­cates tu­mors, in­hibits the deadly dis­ease’s spread and pro­longs sur­viv­al in mice, re­search­ers say.

“This ve­hi­cle, or vec­tor, is so tar­geted and ro­bust… that it can be used for ther­a­py and per­haps for imag­ing” of tu­mors, said Mien-Chie Hung of The Un­ivers­ity of Tex­as M. D. An­der­son Can­cer Cen­ter in Hous­ton, Texas. Hung is sen­ior au­thor of a stu­dy on the ther­apy, pub­lished in the July 9 edi­tion of the re­search jour­nal Can­cer Cell.

Pancreatic cancer cells. (Courtesy U.S. Nat'l Cancer Inst.)
The system is an example of gene ther­apy—the in­ser­tion of genes into the bo­dy in order to cor­rect some ge­ne­tic mal­func­tion. Gene ther­apy is still in its in­fancy de­s­pite some early suc­cesses; the U.S. Food and Drug Ad­min­istra­t­ion has not yet ap­proved any such ther­apies.

Re­search­ers call the new sys­tem for pan­cre­at­ic can­cer a ver­sa­tile ex­pres­sion vec­tor, nick­named VI­SA. It in­c­ludes a gene known to kill can­cer cells, along with mo­le­cu­lar com­pon­ents that tar­get the gene’s ac­t­i­vity to the di­s­ease tissue.

The components are all pack­aged in a fat­ty ball called a li­po­some, which is de­liv­ered in­tra­ve­nous­ly.

“We are work­ing to br­ing it to a clin­i­cal tri­al,” said M. D. An­der­son’s James Ab­bruz­zese, a mem­ber of the re­search team. He es­ti­mates it will take a year or two to com­plete FDA re­quire­ments for a Phase I clin­i­cal tri­al, which could serve as a first step to ap­pro­val.

About 37,000 cases of pan­cre­at­ic can­cer are di­ag­nosed an­nu­ally in the Un­ited States. Early di­ag­no­sis is ex­tremely hard, so the dis­ease is of­ten dis­cov­ered at a late stage af­ter it al­ready has spread, or metas­ta­sized. Few­er than four per­cent of pa­tients sur­vive five years af­ter di­ag­no­sis, one of the low­est can­cer sur­viv­al rates.

In a test of the ther­a­py against two ag­gres­sive lines of pan­cre­at­ic can­cer in two dif­fer­ent types of mice, re­search­ers load­ed the VI­SA sys­tem with a mu­tant ver­sion of a gene named Bik. The gene pro­duces a pro­tein mol­e­cule that nat­u­rally forc­es can­cer cells to kill them­selves. The team cre­at­ed the more le­thal mu­tant and named it BikDD.

Un­treat­ed mice in both ex­pe­ri­ments all died with­in 40 days. The VI­SA-BikDD mice lived much long­er, re­search­ers said, with at least half sur­viv­ing for 14 months with no de­tect­a­ble sign of can­cer re­cur­rence.

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A molecularly engineered therapy embeds a gene in pancreatic cancer cells that shrinks or eradicates tumors, inhibits the deadly disease’s spread and prolongs survival in mice, researchers claim. The findings, from The University of Texas M. D. Anderson Cancer Center in Houston, are reported in the July 9 edition of the research journal Cancer Cell. “This vehicle, or vector, is so targeted and robust… that it can be used for therapy and perhaps for imaging,” said M. D. Anderson’s Mien-Chie Hung, senior author of the study. Researchers call the system a versatile expression vector, nicknamed VISA. It includes a targeting agent, also called a promoter; two components that boost gene activity in the target tissue; and a payload—a gene known to kill cancer cells. It’s all packaged in a fatty ball called a liposome and delivered intravenously. “We are working to bring it to a clinical trial,” said James Abbruzzese of M. D. Anderson. He estimates it will take a year or two to complete U.S. Food and Drug Administration requirements for a Phase I clinical trial. About 37,000 cases of pancreatic cancer are diagnosed annually in the United States. Early diagnosis is extremely hard, so the disease is often discovered at a late stage after it already has spread, or metastasized. Fewer than four percent of pancreatic cancer patients survive five years after diagnosis, one of the lowest cancer survival rates. In a test of the therapy against two aggressive lines of pancreatic cancer in two different types of mice, researchers loaded the VISA system with a mutant version of a gene named Bik, which produces a protein molecule that naturally forces cancer cells to kill themselves. The team created the more lethal mutant and named it BikDD. Untreated mice in both experiments all died within 40 days. The VISA-BikDD mice lived longer, researchers said, with at least half surviving for 14 months with no detectable sign of cancer recurrence.