Disclosed are diagnostic techniques for the detection of human disease states that affect gene expression in peripheral leukocytes. The invention relates particularly to probes and methods for evaluating the presence of RNA species that are differentially expressed in the peripheral blood of individuals with such a disease state compared to normal healthy individuals. The invention further relates to methods for detection of protein species that are differentially expressed in the peripheral blood of individuals with such a disease state compared to normal healthy individuals. Genetic probes, antibody probes and methods useful in monitoring the progression and diagnosis of two specific disease states, prostatic cancer and breast cancer, are described.