CDC4 gene expression as potential biomarker for targeted therapy in prostate cancer.

Targeted therapy of proteasome regulated gene expression has potential utility in cancer treatment since components of ubiquitin-mediated proteolysis are altered in human malignancy. Specific regulators of proteasome degradation such as F-box proteins of the SCF E3 ligase complex are ideal biomarkers for assessing therapeutic efficacy since these components determine substrate specificity. An F-box protein that appears to be important in this process is human Cdc4 (Fbw7) since expression is detected in a variety of human cancers including breast, colon, pancreas and uterus. The role of Cdc4 in tumorigenesis appears to be related at least in part to regulation of cyclin E since inactivating mutations of CDC4 in cancer cells leads to cyclin E overexpression and genomic instability. In order to investigate the potential biological and clinical consequences of proteasome inhibition with respect to Cdc4 mediated targeted proteolysis, we investigated CDC4 expression and genetic alterations in 53 primary human prostate cancers in addition to correlation with relevant histopathological and clinical parameters. We identified genetic alterations in 6% of our prostate cancers while differential expression of Cdc4 isoforms correlated with advanced pathological stage and clinical recurrence. Our data suggest that CDC4 expression in prostate cancer has important biological and clinical implications since genetic alterations, differential Cdc4 isoform expression, histopathological and clinical correlation were demonstrated in our analysis. Therefore molecular genetic analysis of CDC4 expression may be an important biomarker for concurrent or subsequent clinical investigation of proteasome targeted therapy in men with prostate cancer.

Prostate specific antigen as a clinical biomarker for prostate cancer: what's the take home message?

Prostate specific antigen (PSA) continues to be challenged as a legitimate clinical biomarker in early detection of prostate cancer due to lack of specificity for malignant transformation. Skepticism surrounding the utility of serum PSA as a clinical marker is not new and many questioned its initial use in widespread prostate cancer screening due to non-specific expression and low predictive value for cancer detection. Despite these initial concerns, serum PSA measurement along with digital rectal examination (DRE) is currently the accepted practice for prostate cancer screening in the United States with hundreds of thousands of men undergoing serum PSA measurement annually. In contrast to its role for early detection, serum PSA measurement as a surrogate for prostate cancer recurrence (biochemical failure) following curative intent therapy has consummate clinical utility in post-treatment surveillance. As thousands of men each year are aggressively treated for potentially curable prostate cancer, development of simple and effective diagnostic tools for detecting treatment failures should be an important area of biomedical and clinical investigation. We have constructed and tested a home-based prostate cancer surveillance device for use by patients to detect PSA from blood obtained by finger stick. Our initial results suggest that home based PSA testing is feasible and may have clinical utility in management of men treated for prostate cancer.

Microsatellite instability and loss of heterozygosity have distinct prognostic value for testicular germ cell tumor recurrence.

Germ cell tumor (GCT) is the most common genitourinary malignancy of men between the ages of 18 and 35 years. Therapy is ultimately successful in over 90% of patients, however significant morbidity and mortality can be associated with adjuvant treatment and relapse. Molecular markers that predict treatment response and/or poor outcome would have immediate clinical benefit since adjuvant treatment could be selectively reserved for patients at higher risk for relapse and those patients most likely to respond to treatment. In order to identify potential prognostic molecular markers, we evaluated 118 GCT for microsatellite instability (MSI), loss of heterozygosity (LOH) and MSH2 immunostaining to identify tumors associated with relapse and/or poor outcome following initial surgical, medical and/or radiation therapy. MSI in 3 or more markers and/or low MSH2 staining were associated with relapse while LOH in the absence of MSI and/or high MSH2 staining were not. Twenty-five percent of GCT exhibited genetic instability in 3 or more microsatellite markers (MSI+ tumors), 15% exhibited LOH in the absence of MSI (LOH only tumors) and 44% exhibited decreased or absent MSH2 immunostaining (low MSH2 staining tumors). Thirty-six patients (30%) relapsed and 27 of these patients (75%) had MSI+ and/or low MSH2 staining tumors. Only one patient (3%) with an LOH only tumor and no patients with high MSH2 staining and LOH only tumors relapsed. Therefore distinct GCT subpopulations identified by detection of MSI, LOH and MMR expression are associated with different clinical outcomes. MMR deficient testicular GCT with increased frequency of MSI had an increased association with tumor recurrence compared to GCT with an intact MMR system and LOH in the absence of MSI.

Mismatch repair gene expression and genetic instability in testicular germ cell tumor.

Human mismatch repair (MMR) genes encode highly conserved interacting proteins that correct replication errors predisposing to hereditary gastrointestinal and genitourinary malignancies. A subset of sporadic genitourinary tumors also exhibits MMR deficiency and can be identified by measuring the frequency of microsatellite instability (MSI) in cancer cell DNA. We investigated expression of the two most commonly mutated MMR genes, MSH2 and MLH1, in sporadic testicular germ cell tumor (GCT) in order to: (1) determine the expression pattern of MSH2 and MLH1 proteins in normal seminiferous tubules and histologically distinct GCT subtypes, (2) correlate MMR gene expression with genetic instability in GCT and (3) develop a panel of molecular markers that can identify genetically distinct subsets of GCT for prognostic assessment. MSH2 and MLH1 had differential staining patterns in normal seminiferous tubules and malignant tissues. MSH2 was expressed in all stages of spermatogenesis up to but excluding mature sperm whereas MLH1 was predominantly expressed in premeiotic germ cells. All histological GCT subtypes showed differential immunostaining for MSH2 and MLH1 however pure seminoma had statistically significant fewer low MSH2 staining tumors than other subtypes (p = 0.046). Twenty-five percent of GCT exhibited increased frequency of MSI (MSI+ tumors) with 73, 70 and 43% of MSI+ tumors exhibiting low MSH2, low MLH1 or low MSH2 and low MLH1 staining respectively. Fifteen percent of testicular GCT exhibited loss of heterozygosity (LOH) but no MSI (LOH only tumors). Only 28, 17 or 6% of LOH only tumors exhibited low MSH2, low MLH1 or low MSH2 and low MLH1 staining respectively.