New York: Scientists, including Indian-origin researchers, have developed a new therapy that uses radioactive bacteria to attack tumour cells in aggressive pancreatic cancer without harming healthy tissue.Researchers at Albert Einstein College of Medicine of Yeshiva University in New York used Listeria bacteria to selectively infect tumour cells and deliver radioisotopes into them.The experimental treatment dramatically decreased the number of metastases (cancers that have spread to other parts of the body) in a mouse model of highly aggressive pancreatic cancer without harming healthy tissue."We`re encouraged that we`ve been able to achieve a 90 per cent reduction in metastases in our first round of experiments," said co-senior author Claudia Gravekamp, associate professor of microbiology & immunology at Einstein.In a previous study, Gravekamp found that an attenuated (weakened) form of Listeria monocytogenes can infect cancer cells, but not normal cells because tumour microenvironment suppresses the body`s immune response, allowing Listeria to survive inside the tumours.By contrast, the weakened bacteria are rapidly eliminated in normal tissues.Gravekamp set out to investigate Listeria-tumour interactions and how Listeria could be used to attack cancer cells.The idea of attaching radioisotopes (commonly used in cancer therapy) to Listeria was suggested by Ekaterina Dadachova, professor of radiology and of microbiology & immunology at Einstein and the paper`s co-senior author.Working together, Gravekamp and Dadachova coupled a radioactive isotope called rhenium to the weakened Listeria bacteria."We chose rhenium because it emits beta particles, which are very effective in treating cancer. Also, rhenium has a half-life of 17 hours, so it is cleared from the body relatively quickly, minimising damage to healthy tissue," said Dadachova.Mice with metastatic pancreatic cancer were given intra-abdominal injections of the radioactive Listeria once a day for seven days, followed by a seven-day "rest" period and four additional daily injections of the radioactive bacteria.After 21 days, the treatment had reduced the metastases by 90 per cent compared with untreated controls.In addition, the radioactive Listeria had concentrated in metastases and to a lesser extent in primary tumours but not in healthy tissues, and the treated mice did not appear to suffer any ill effects.
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