Even though prostatic adenocarcinoma is the second leading cause of cancer death among American men, therapeutic options for advanced disease remain limited. Consequently, there is great interest in developing novel immunotherapy approaches to attack several of the prostate cancer-associated antigenic peptides identified over the past two decades.
Prostate stem cell antigen (PSCA) has long been considered one of the most attractive targets for this disease because it is overexpressed in a large percentage of advanced prostate cancers, but is absent in the majority of normal tissues. Now, an article by Garcia-Hernandez and colleagues in Cancer Research reports that a PSCA-based vaccine provides long-term protection against prostate cancer progression in one of the best mouse models of the disease.
A 123-amino acid protein of unknown function, human PSCA is overexpressed in at least a third of primary prostate cancers and essentially all those metastatic to bone. Moreover, increasing levels of PSCA strongly correlate with higher tumor grade/stage and progression to antigen independence.
Recently, a murine homologue of PSCA was discovered and found to be highly expressed in tumor cells of the transgenic adenocarcinoma mouse prostate (TRAMP) cancer model. Genetically engineered to express a strong oncogene in the prostate from the time of birth, TRAMP mice develop prostatic intraepithelial neoplasia (PIN) by 8 weeks and universally succumb to metastatic prostate carcinoma by one year of age.
In the current study, the researchers show that TRAMP mice vaccinated against PSCA at the time of PIN development had a 90% survival rate at 12 months of age and no evidence of autoimmunity or other adverse effects from the vaccine.
These remarkable results suggest that vaccination against PSCA at the earliest signs of prostate cancer holds promise as a therapeutic strategy against this disease.
Medical Writer, MDLinx OncologyMedical Writer, MDLinx Oncology
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