Inhibition of tumourigenicity and metastasis of prostate cancer by suppressing the expression of C-FABP gene plus androgen depletion

• Main Author: Morgan, Elwin Alex
• Published: University of Liverpool 2005
• Subjects: 616.9946307
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425440

Prostate cancer is the most commonly occurring form of non-tobacco related cancers of man in the developed world. Our understanding of the molecular pathology of prostate cancer is currently very limited. At present, clinical therapy focuses on androgen blockage by physical or pharmaceutical castration. Previous work in our molecular pathology laboratory has led to the identification of several genes whose elevated expression may contribute to the malignant progression of the prostate cancer cells. One such gene is that coding for human cutaneous fatty acid binding protein (C-F ABP). The work described in this thesis is aimed to study the specific role of C-F ABP on the tumourigenicity of prostate cancer, to investigate whether the elevated expression of C-FABP is related to androgen sensitivity of the cancer cells, and to explore the therapeutic possibility of inhibiting the development and expansion of prostate cancer through suppressing the expression of C-F ABP gene combined with the androgen depletion. To investigate the biological significance of elevated expression of C-FABP in prostate cancer, CFABP expression in highly malignant prostate cancer cells PC3M was suppressed by the transfection ofa reverse transcript ofCFABP. Two antisense transfectant cells, C-FABP-PC3M-l and C-FABP-PCM-3 were produced with 3.8 fold and 6.9 fold reduction in normal C-FABP expression respectively. Exploration of tumourigenic potential of transfectant cells by invasion assay showed that 7% of antisense transfectant cells invaded the ECM, compared to 14% of control transfectant cells. Subcutaneous inoculation of antisense and control transfectant cells into immuno-compromised male nude mice demonstrated a significant reduction in tumour incidence and tumour volume in antisense transfectant cells compared to control transfectant tumours. Previous work in our laboratory showed that C-FABP was over-expressed in androgen independent prostate cancer cells. To investigate whether elevated C-FABP expression is related to androgen sensitivity, C-FABP expression was reduced by 95% by RNA interference in highly malignant androgen independent prostate cancer cells PC3M to study the effect of suppressed CFABP expression and androgen deprivation on prostate cancer cells. In vitro assays for cell proliferation and colony formation show signi ficant differences in cell growth rate and number of colonies formed in androgen positive and negative conditions, however, comparisons between the two conditions suggest that C-F ABP may not have some bearing on androgen sensitivity in vitro. Subcutaneous inoculation of RNAi transfectant cells into male immuno-compromised nude mice produced a significant reduction in tumour incidence and mean tumour volume in RNAi transfectant group 75% (3/4 animals) and 176mm3 compared to that of the parental PC-3M group which produced 100% (4/4 animals) tumour incidence and 1471mm ' mean tumour volume respectively. However, castration of mice and orthotopic implantation of RNAi transfectant cells and parental PC-3M cells into the prostate gland of mice produced 100% (4/4 animals) tumour incidence compared to 0% (0/3 animals) observed in the RNAi transfectant group. At autopsy, mice were dissected and primary tumours, lungs, heart and liver were removed for haematoxylin and eosin staining. From these groups, only the castrated and orthotopically implanted parental PC-3M cell group produced secondary micro-metastasis in the lungs and liver of mice (4/4 animals). This data suggest that suppressed CF ABP activity may not restore androgen sensitivity in highly malignant androgen insensitive PC3M cells ill vitro. However, ill vivo studies suggest that the combination of suppressed CFABP and androgen depletion have a synergistic effect resulting in enhanced suppression of tumourigenicity and metastasis.