Photodynamic Therapy-Adjunctive Therapy in the Treatment of Prostate Cancer

Abstract

The alarming increase in the number of advanced-stage prostate cancer cases with poor prognosis has led to a search for innovative methods of treatment. In response to the need for implementation of new and innovative methods of cancer tissue therapy, we studied photodynamic action in excised prostate tissue in vitro as a model for photodynamic therapy. To ascertain the effects of photodynamic action in prostate tissue, Rose Bengal (0.01 to 0.05 mM) was used as a photosensitizer in the presence of oxygen and light to generate singlet oxygen in tissues in vitro. Five preset concentrations of Rose Bengal were chosen and injected into prostate tissue samples (60 samples with 12 replications for each RB concentration) that were subsequently exposed to 532 nm light. The effects of irradiation of the Rose Bengal infused tissue samples were determined by histopathological analysis. Histopathological examination of prostate samples subjected to photodynamic action revealed numerous changes in the morphology of the neoplastic cells and the surrounding tissues. We conclude that the morphological changes observed in the prostate cancer tissues were a result of the photogeneration of cytotoxic singlet oxygen. The tissue damage observed post photodynamic action offers an incentive for continued in vitro investigations and future in vivo clinical trials.

Keywords: adjuvant therapy; in vitro methods; photodynamic therapy; prostate cancer.

Figure 1

Mechanism of photodynamic ROS generation.

Figure 2

Bar plot of Rose Bengal concentration.

Figure 3

Experimental setup for in vitro irradiation of prostate tissue. Image (A) shows an image of the laser power source. Image (B) shows irradiation of a prostate cancer tissue sample with laser light.

Figure 4

Prostate cancer tissue after PDT with different concentration of RB. Arrows indicate the observed changes presented in the description. Upon application of 0.01 mM RB (A), discrete chromatin condensation in most of the cancer cell nuclei and swelling of the stroma are visible. Predominantly normal prostate cancer cells illustrate the irregular arrangement and size of the cells. The architecture of the glands is virtually unchanged, and some cancer cells still have distinct nucleoli. Visible contours of the nuclear membrane. Thrombotic necrosis developed upon application of a concentration of 0.02 mM RB (B). In addition to the dense cytoplasmic areas, lighter zones that have a pinkish color after treatment with Rose Bengal were detected. PDT with the application of Rose Bengal at a concentration of 0.03 mM (C) showed mild chromatin condensation, irregular shape of the nuclei, and significant architectural disturbances. The cells shown are surrounded by dark cells that stain much more intensely. After the application of 0.04 mM RB (D), mild to massive chromatin condensation, pyknotic nuclei, and significant architectural disturbances were observed. These changes were also accompanied by swelling and the presence of protein in the stroma. Fragment of epithelium in a small percentage of cells with the presence of homogeneous chromatin with almost complete loss of chromatin granularity was observed. In the last stage after the application of 0.05 mM RB (E), enhanced traits of cell damage and necrosis, which are easily identified. Cell nuclei and whole cells stick together, which makes them indistinguishable. There is also swelling and the presence of protein in the stroma. All microscopic images are at 63× magnification. Histological examination of prostate tumor tissues showed PDT damage to the testicular cells of the tumor cells.