Preventive vaccine against prostate cancer – "mouse version"
Scientists at the University of Southern California, working under the leadership of Professor Martin Kast, have developed a vaccine against prostate cancer that prevents the formation of tumors in 90% of young mice genetically predisposed to this disease.
Today, men who are diagnosed with an increasing level of prostate–specific antigen (PSA) in the blood – a marker of prostate cancer - are advised to closely monitor the state of the prostate, without taking any action before symptoms appear. The authors believe that vaccination carried out in an asymptomatic period can radically change the course of the disease.
The approach proposed by the authors is based on stimulation of the immune response against prostate stem cell antigen (prostate stem cell antigen, PSCA), which is the target of a number of therapeutic vaccines currently being developed for the treatment of progressive and unresponsive to traditional methods of tumor treatment. PSCA is a membrane protein, the high expression of which is observed in about one third of early prostate tumors, but as it grows and progresses, the expression of this protein increases in all tumors of this organ. A low level of PSCA expression is characteristic of normal prostate tissue, as well as bladder, colon, kidneys and stomach.
Scientists have developed a vaccination scheme in which 8-week-old mice genetically predisposed to the development of prostate cancer were injected with two types of vaccines. The first vaccination consisted in the introduction of a DNA fragment encoding PSCA, which caused an initial reaction from the immune system. Repeated vaccination was carried out 2 weeks later. At the same time, the animals were injected with a modified virus, in the genome of which the PSCA gene was embedded. Such a twofold multidirectional effect on the immune system caused the development of stable immunity.
Only 2 out of 20 mice in the experimental group developed malignant prostate tumors by the age of one year, while all animals in the control group died. At the same time, the tumors of the experimental group of mice were tiny, non-increasing nodules surrounded by a huge number of immune cells. Thus, vaccination has turned cancer into a chronic treatable disease.
This vaccination strategy is also effective against other antigens. Vaccination against another prostate cancer antigen for 1.5 years saved the life of 65% of mice in the experimental group, and, most likely, the rest of the animals died of old age.
It is also important that vaccination did not cause the development of an autoimmune response against antigens expressed in small amounts by normal body tissues.
The authors believe that their proposed approach has a great future, but they emphasize that it is necessary to conduct clinical trials, including to exclude the possibility of developing autoimmune reactions.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily.
06.02.2008