Stem cells are present in many common tumour types, including the prostate. Biological evidence supports the involvement of stem cells in the development and progression of leukaemia, lung, stomach, breast and brain cancers. The identification of these cells can now explain both the heterogeneity of prostate tumours and the variable response of the tumour to conventional therapies.

Cancer stem cells exhibit biological characteristics which render them refractory to many current therapeutic strategies. Nature has endowed stem cells with biological attributes which provide in-built resistance to environmental effects and which protect them from changes which could threaten their integrity and function. For example, stem cells exhibit robust protective transport mechanisms which the cell uses in its defence, including protection against man-made xenobiotics. The relative metabolic silence (quiescence) of cancer stem cells compared to their proliferating progeny which comprise the majority of cells in a tumour, renders cancer stem cells relatively resistant to conventional therapies (see Figure 1 below). The persistence of therapy resistant stem cells explains the recurrence of tumours in patients who may have shown initial improvements in their condition.

Figure 1 Prostate Stem Cells (CSCs) and Therapy

Cancer stem cells might therefore be likened to “biological time bombs”, which if not destroyed during therapy, allow the disease to re-establish itself (Figure 2).

Figure 2 A Stem Cell View of Tumour Recurrence

The cornerstone of Pro-Cure’s research and development, shared by many leading researchers, is that therapies directed against tumour stem cells offer the prospect of a long-term cure, rather than a palliative therapy for prostate cancer.

Stem cells comprise at most 0.1% of the cells in prostate tumours. The complexity involved in isolating, handling and studying these cells has made their study extremely challenging, and the field is vibrant and sometimes controversial. The development of new and advanced techniques for the isolation and study of prostate cancer stem cells has been central to the research carried out by Professor Norman Maitland and co-workers in the YCR Cancer Research Unit. This expertise and knowledge, which is at the forefront of stem-cell research, together with the group’s gene profiling programme, has created new opportunities at the leading edge of prostate cancer research.

A popular review in Scientific American (July, 2006) underlines the importance of stem cells in cancer, where the authors, Michael W Clarke and Michael F. Becker, conclude “the implications of a stem cell model for the way we understand cancer is dramatic. Current therapies take aim against all tumour cells, but our studies and others have shown that only a minor fraction of cancer cells have the ability to reconstitute and perpetuate the malignancy. If traditional therapies shrink a tumour but miss these cells, the cancer is likely to return. Treatments that specifically target the cancer stem cells could destroy the engine driving the disease, leaving any remaining non-tumorigenic cells to eventually die off on their own”. This and other recent publications provide timely support to Pro-Cure’s own long-established conclusions relating to prostate cancer, and the role of cancer stem cells in the progression of this disease.

The global structure of Prostate Cancer R&D is one of the most comprehensive and up to date information sources available in the cancer field and indicates new and emerging therapies which include siRNA, monoclonal antibodies, gene therapy, antigen or cellular-based vaccines, hormones, apoptotic and chemotherapeutic drugs. More than 160 companies are active in the prostate cancer field and data is available from more than 300 industry-related prostate cancer projects, 170 clinical trials and more than 130 preclinical projects. Few, if any, of these are likely to affect the cancer stem cells.