Quantitative cellular methods in the evaluation of prostate cancer

Abstract

The distinction between those prostate cancers rapidly progressing and leading to death and those with little likelihood of causing death in cancer is a major goal in current prostate cancer research. Morphological tumor characteristics at present are the basis for evaluation of the prognosis of the disease. Visual analysis of tumor provides, however, only limited information on the prognostic potential of the tumor. Therefore, efforts have been made to supplement conventional morphology by quantitative measurements. This study focused on development and application of new methods to measure morphological features related to the biological potentials of the prostatic carcinoma.

Morphological properties of the nucleus of prostate carcinoma and benign hyperplasia were evaluated by image analysis. Nuclear area and variation in size differed significantly between the benign and malignant prostate, and this difference increased further at the shift from diploid to aneuploid tumor. In the follow-up, however, nuclear factors did not reach independent prognostic significance.

We developed a method to measure the cellular DNA content on slides by fluorescence image cytometry. This method was compared with flow-cytometry and was used for ploidy and cell cycle analysis in primary tumors of the prostate and lymph nodes metastasis.

Tumor heterogeneity was studied by DNA cytometry and morphology in multiple biopsies from the prostate. Underestimation of the aggressiveness of the prostate carcinoma was minimized by simultaneous studies of tumor grade and DNA-ploidy more than by increasing the number of biopsies.

For quantitation of tissue PSA, the immune reaction of tissue PSA was measured simultaneously with the amount of cellular DNA, by double fluorescence image cytometry in archival tissue sections of the prostate. Tissue PSA decreased significantly with increase of tumor grade, Gleason score and shift from diploid to aneuploid tumor.

For investigation of cell proliferation, we developed a new antibody against the thymidine kinase I as a specific marker of cell proliferation. The marker was studied in relation to the cell cycle, and its cellular localization, and applied for investigations of the archival tissue sections of benign prostate, prostatic intraepithelial neoplasia and carcinoma of the prostate. From the comparison between the fraction of thymidine kinase I positive cells, the MIB-1positive cell fraction and the fraction of cells in S+G2 in cell cycle, we concluded that thymidine kinase 1, in addition to S+G2 cells in cell cycle, is also expressed in the late G1. The fraction of late G1 cells increased with the size of S+G2 fraction.

In conclusion, quantitative cellular methods supply the visual evaluation of prostate cancer by reproducible and objective findings. Quantitative methods are a prerequisite for further understanding the malignant behavior, for instance in prostate cancer.