Emily A. Matuszak and Natasha Kyprianou
Departments of Toxicology, Urology and Biochemistry, University of Kentucky College of Medicine, Lexington, KY, USA
Radical prostatectomy is among the most successful treatment modalities for patients exhibiting clinically localized prostate cancer. Despite this, roughly one-third of all radical prostatectomy patients will experience biochemical recurrence following prostatectomy. Curing prostate cancer requires a greater understanding of distinct biological events that differentiate prostate cancer from advanced life-threatening disease. Thus, a current challenge facing the clinical management of prostate cancer is the need for novel prognostic biomarkers capable of predicting biochemical recurrence to direct therapeutic interventions at earlier disease stages.
The oncogenic epithelial–mesenchymal transition (EMT) plays a critical role in metastatic prostate cancer progression . EMTs engender coordinated molecular and genetic events which provoke phenotypic transformations that are indicative of the acquisition of mesenchymal characteristics which yield altered cellular behaviours . Such altered behaviours may include but are not limited to enhanced migratory capability, increased invasive capacity, heightened resistance to apoptosis and conferred stem-like properties [3,4]. Conversion of an epithelial-derived prostate cancer cell to a more mesenchymal-like state has recently been implicated in prostate tumourigenesis as a mechanism facilitating the progression to metastatic castration-resistant disease .While alterations in the expression profiles of numerous EMT-associated transcriptional regulators and their molecular targets have served as biomarkers for studying EMT programmes, less is known about the contributions of EMTs in the emergence of treatment failure and tumour recurrence. Recently, EMT has been suggested to be a programme involved in metastatic disease progression that may also profoundly influence therapeutic outcomes amongst patients. Thus, it may be advantageous to develop predictors for risk assessment among prostate cancer patients that include specific EMT-associated markers in clinical evaluations.
Despite our current lack of knowledge regarding the clinicopathological significance of EMT, the potential value of an EMT marker signature as a prognostic indicator of biochemical recurrence among prostate cancer patients has emerged with some promise. Behnsawy et al. establish an initial path towards estimating the clinical value of assessing EMT marker levels in tandem with conventional clinicopathological prognostic factors in radical prostatectomy specimens from patients with organ confined prostate cancer, without any neoadjuvant therapy. Their evaluation follows a robust profile and results intriguingly reflect a pattern that may facilitate prediction of biochemical recurrence among patients. Using an exhaustive immunohistochemical analysis, the expression patterns of 13 EMT markers were evaluated in 197 radical prostatectomy specimens of which the expression levels of two EMT-associated markers, Twist and vimentin, were the most promising factors for such predictions.
The novel aspect and translational significance of this study are both reflected in the homogeneity of the patient population, in terms of localized organ confined disease. It represents an initial step towards recognizing an expression signature for specific EMT-associated factors in the therapeutic outcome of localized prostate cancer, but not disease progression. While the clinical impact of the reported findings may not be fully apparent, one may begin to speculate the promise of incorporating EMT-associated biomarkers in a clinical setting to facilitate diagnosis, prognosis and/or directing treatment strategies among patients. Primary endpoints of acquisition of an EMT phenotype following androgen axis targeting treatment must be clearly defined in the design of future clinical trials for the treatment of prostate cancer patients, with caution being given to selection of biopsy specimens vs radical prostatectomy specimens at an ‘optimal’ EMT window and in order to mitigate bias in tissue sampling resulting from long duration of therapeutic intervention. Control groups will provide valuable biological material to identify alternative mechanisms of treatment resistance (MAPK signalling). The statistical power in the relatively large cohort analysed enhances our confidence in considering the EMT landscape as an attractive platform for prediction of therapeutic response in future clinical trials. The concern, however, of whether improved prediction of biochemical recurrence by EMT profiling in pretreatment biopsies justifies its integration in the clinicopathological parameters (Gleason score, PSA) remains. Thus high expectations and much promise surround the pathological exploitation of EMT biomarkers (as signatures) in identifying profiles of tumour aggressiveness and providing a significant contribution in our quest towards the development of personalized therapies in prostate cancer patients with advanced disease.
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