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Bacteria may help pummel one of toughest cancers

April 23, 2013
Courtesy of PNAS
and World Science staff

A weak­ened, ra­di­o­ac­t­ive strain of bac­te­ria can help fight tu­mors in mice with pan­cre­at­ic can­cer, one of the hard­est to beat, re­search­ers re­port.

The sci­en­tists said they cut the num­ber of met­a­stat­ic tu­mors by 90 per­cent, with­out harm­ing healthy cells, by us­ing the bac­te­ria to de­liv­er a deadly “ra­di­o­ac­t­ive pay­load” to tu­mor cells.

Listeria monocytogenes bacteria. Sci­en­tists said they cut the num­ber of met­a­stat­ic pan­creat­ic tu­mors in mice by 90 per­cent, with­out harm­ing healthy cells, by us­ing the bac­te­ria to de­liv­er a deadly “ra­di­o­ac­t­ive pay­load” to tu­mor cells.


Pan­cre­at­ic can­cer of­ten spreads to dis­tant or­gans even be­fore the orig­i­nal tu­mor grows large enough to be de­tected. The newer tu­mors that re­sult are called met­a­stat­ic tu­mors. 

There are no ef­fec­tive treat­ments once the dis­ease spreads, and the five-year sur­viv­al rate has re­mained a mea­ger at 4 per­cent for the past quar­ter cen­tu­ry, ac­cord­ing to the re­search­ers, who pub­lished their find­ings in this week’s early on­line is­sue of the jour­nal Pro­ceed­ings of the Na­tio­n­al Aca­de­my of Sci­en­ces

The sci­en­tists, Clau­dia Gravekamp at the Al­bert Ein­stein Col­lege of Med­i­cine in New York and col­leagues, ex­plored wheth­er a bac­te­ri­um called Lis­te­ria mono­cy­to­genes could home in on the immune-compromised tu­mor “mi­croen­vi­ron­ment.”

They in­jected a strain of the bac­te­ri­um in­to mice that had been caused to deve­lop pan­cre­at­ic tu­mors. They found the bac­te­ria grew quickly in met­a­stat­ic tu­mors, slowly in pri­ma­ry tu­mors, and not at all in healthy tis­sues. 

The re­search­ers then at­tached a ra­di­o­ac­t­ive el­e­ment called 188 Rhe­ni­um to the bact­eria. Af­ter sin­gle in­jec­tions eve­ry day for a week, fol­lowed by a week of rest, then sin­gle in­jec­tions on four more days, the au­thors said they ob­tained a 90 per­cent re­duc­tion in the num­ber of met­a­stat­ic tu­mors and a 64 per­cent re­duc­tion in pri­ma­ry, or orig­i­nal, tu­mors.

Nei­ther radia­t­ion nor Lis­te­ria were de­tect­a­ble a week af­ter treat­ment, and the ro­dents suf­fered no sig­nif­i­cant side ef­fects, they added, sug­gest­ing the find­ings might lead to a good treat­ment for met­a­stat­ic pan­cre­at­ic can­cer.

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A weakened, radioactive strain of bacteria can help fight tumors in mice with pancreatic cancer, one of the hardest to beat, researchers report. The scientists said they cut the number of metastatic tumors by 90%, without harming healthy cells, by using the bacteria to deliver a deadly “radioactive payload” to tumor cells. Pancreatic cancer often spreads to distant organs even before the original tumor grows large enough to be detected. The newer tumors that result are called metastatic tumors. There are no effective treatments once the disease spreads, and the five-year survival rate has remained a meager at 4% for the past quarter century, according to the researchers, who published their findings in this week’s early online issue of the journal pnas. The scientists, Claudia Gravekamp at the Albert Einstein College of Medicine in New York and colleagues, explored whether a bacterium called Listeria monocytogenes could home in on the immune-compromised tumor “microenvironment.” They injected a strain of the bacterium dubbed Listeriaat into rodents with pancreatic tumors. They found the bacteria grew quickly in metastatic tumors, slowly in primary tumors, and not at all in healthy tissues. The researchers then attached a radioactive element called 188 Rhenium to Listeriaat. After single injections every day for a week, followed by a week of rest, then single injections on four more days, the authors said they obtained a 90% reduction in the number of metastatic tumors and a 64% reduction in primary, or original, tumors. Neither radiation nor listeria were detectable a week after treatment, and the animals suffered no significant side effects, they added, suggesting the findings might lead to a good treatment for metastatic pancreatic cancer. n