Current status of gene therapy for prostate and bladder cancer

Adenovirus mediated gelsolin gene therapy for orthotopic human bladder cancer in nude mice

PURPOSE

Gelsolin is an actin regulatory protein that is undetectable or reduced in human bladder tumors compared with normal epithelial cells. Whether the over expression of gelsolin could inhibit tumor growth was investigated in an orthotopic bladder cancer nude mouse model using recombinant adenovirus encoding wild-type gelsolin (Ad-GSN).

MATERIALS AND METHODS

The 2 human bladder cancer cell lines KU-7 and UMUC-2 were transduced with Ad-GSN in vitro. Flow cytometric analysis was done to examine the cell cycle after transducing the adenovirus. Cell growth was compared with control groups of these cells transduced with adenovirus containing the Escherichia coli beta-galactosidase gene Ad-betagal. In vivo KU-7 cells were introduced into the bladder of nude mice (day 0), followed by 3 injections into the urethra (days 2 to 4) with Ad-GSN or Ad-betagal (1 x 10 pfu). At 8 days after initial adenovirus exposure (day 10) each bladder was sectioned and stained, and the mass of the tumor was digitally determined.

RESULTS

Bladder cancer cell growth (KU-7 and UMUC-2) was inhibited after these cells were transduced with Ad-GSN in vitro. Based on flow cytometric analysis over expression of gelsolin may cause these cells to arrest or delay at the G2/M phase of the cell cycle. In the orthotopic bladder cancer model the mass of the tumor was approximately 90% less in Ad-GSN treated animals than in controls.

CONCLUSIONS

Ad-GSN provides a significant tumor suppressive effect on human bladder cancer cells in this orthotopic nude mouse model. Adenovirus mediated over expression of gelsolin may be useful therapy for human bladder cancer.

Prevention and treatment of urothelial premalignant and malignant lesions

Bladder cancer is believed to develop through reversible premalignant stages followed by irreversible steps, and ending in invasive cancer giving rise to distant metastases. Because of the variation in the clinical course it has also been suggested that different forms of cancer develop along different molecular pathways leading to tumor presentations of various malignant potential. Today we treat and prognosticate bladder cancer on the basis of clinical and histologic findings that are insufficient to assess all the biologic potential of these tumors. Understanding the pathogenesis of bladder cancer might lead to a more precise identification of particular tumors with regard to clinical aggressiveness, resulting in individualized strategies for treatment and prophylaxis. Bladder cancer is seldom diagnosed in its preclinical stage, it is instead detected at cystoscopy and virtually never recognized as an incidental finding on autopsy. Therefore its "natural history" largely reflects that of "treated" disease. The true incidence of premalignant and malignant epithelial changes is not known. Incidences of hyperplasia and dysplasia of approximately 10% and approximately 5%, respectively and only occasional findings of cancer itself were reported in two autopsy series. Urothelial dysplasia is generally believed to be premalignant and a putative precursor of invasive cancer but unfortunately there has been a lack of standardization in terms of terminology and diagnosis. There is also a need for an agreed definition of the boundary between premalignancy, i.e. urothelial changes that have some but not all the features of carcinoma in situ, and malignancy, especially when considering potentially harmful treatments to prevent this transition. Most new diagnostic tools available and being tested today compare new detection techniques with traditional methods such as cytology or conventional histology of malignant rather than premalignant changes. There is probably also a short preclinical latency, as implied by the incidental findings of bladder cancer at autopsy, which makes it necessary to define how and when to promote early detection and treatment. Future studies therefore have to concentrate on methods for early detection of disease as well as characterization of host susceptibility, evaluation of exposure to carcinogens and potential effects of preventive measures. It is also likely that the improved tools of molecular prognostication will allow us to design trials more precisely in order to tailor therapeutic strategies.

Oncolytic viral therapy for human prostate cancer by conditionally replicating herpes simplex virus 1 vector G207

Over the last few years, a conditionally replicating herpes simplex virus 1 (HSV-1) vector, G207 has been used for the treatment of several malignant tumors. In this article we evaluate the anti-tumoral effect of G207 against prostate cancer in vitro and in vivo. The susceptibility of the human prostate cancer cell lines, DU145 and PC3 to G207 at a multiplicity of infection (MOI) of 0.1 was examined. In addition, the growth characteristics of G207 were assessed. Athymic mice with s.c. tumors were inoculated in vivo intraneoplastically with 1 x 10(7) plaque-forming units (PFU) of G207. For the pathological analyses, s.c. tumors were stained with X-gal. DU145 and PC3 were efficiently destroyed by G207 within 7 days. The viral yields of G207 increased time-dependently. In vivo, the intraneoplastic inoculation of G207 induced a significant inhibition of the tumor growth. The mean tumor growth ratio was significantly inhibited in the G207-treated tumors (DU145, P < 0.0001; PC3, P < 0.001 versus controls). In a pathological study, many lacZ-positive cells were diffusely present in the G207-treated tumors. G207 showed a significant antitumoral effect against human prostate cancer cell lines, and thus may be considered a useful agent for the treatment of prostate cancer.

Endocrine treatment in prostate cancer

Over its natural course, prostate cancer is a heterogeneous tumour with a generally slow but constant rate of growth. The androgen dependence of the prostate gland was demonstrated more than half a century ago by the landmark studies of Professor C. Huggins and colleagues. They established that androgens are implicated not only in growth regulation of the normal gland but also in the pathogenesis of prostate cancer, and that this malignant tissue retains some degree of androgen dependence. This concept was supported by studies of symptomatic clinical cancer, with androgen ablative therapy bringing relief to the patient in more than 80% of the cases. The classical treatment consisted of either bilateral orchiectomy, or administration of diethylstilbestrol (DES). Other forms of therapy followed, involving successive waves of new compounds that either withdrew androgen support from the cancer or blocked the androgens from their receptors in the prostate cancer cells. Chronologically, the progestagens can be well recognised, with one in particular: The successful derivative, cyproterone acetate (CPA). There also have been a number of oral vs. parenteral estrogens, the development of the luteinizing hormone-releasing hormone agonists (LH-RHA), the introduction of the non-steroidal anti-androgens characterised by flutamide and casodex, and more recently, the introduction of the LH-RHA. Moreover, there have been multiple possible forms of combination treatment to obtain maximal androgen blockade (MAB). However, no major differences in treatment outcome have been reported during the last 5 decades and most treatment choices have been based on tradition, associated side effects, the preferences of a particular doctor and patient, together with economic considerations. Furthermore, endocrine treatment has never been shown to cure clinical prostate cancer, which consequently has led to initiatives to defer endocrine treatment or to use it intermittently or use it as a form of neo-adjuvant or adjuvant treatment with surgery or radiotherapy. The history of endocrine therapy is replete with clinical trials that do not represent the patient population in general, and these trials share the clinical fact that they ignore the 20% to 30% of all patients who lack an initial response to a given endocrine treatment. Thus, it is no wonder that prognostic factors determine the outcome more than the treatment itself. Important to current endocrine treatment, however, is the shift to earlier stages of prostate cancer at initial diagnosis. Integration of endocrine treatment at this earlier phase in the pathogenesis of prostate cancer will substantially alter the treatment strategy in relation to long-term benefit with regard to survival, associated side effects, and costs. This complex adjustment is enhanced by recent discoveries in the molecular biology of the prostate which show, on the one hand, that the dihydrotestosterone-androgen receptor (DHT-AR) complex is important in the regulation of gene expression, but also that a number of intrinsic factors (e.g., peptide growth regulatory factors) can, through various paracrine, autocrine or intracrine interactions, exercise a major influence on cellular homeostasis and the regulation of prostatic growth.