Konstantinos Mavridis

Kallikrein-related peptidases in prostate, breast, and ovarian cancers: from pathobiology to clinical relevance

Abstract Tissue kallikrein (KLK1) and kallikrein-related peptidases (KLK2–15) comprise a family of 15 highly conserved secreted serine proteases with similar structural characteristics and a wide spectrum of functional properties. Both gene expression and protein activity of KLKs are rigorously controlled at various levels via diverse mechanisms, including extensive steroid hormone regulation, to exert their broad physiological role. Nevertheless, deregulated expression, secretion, and function of KLK family members has been observed in several pathological conditions and, particularly, in endocrine-related human malignancies, including those of the prostate, breast, and ovary. The cancer-related abnormal activity of KLKs upon substrates such as growth factors, cell adhesion molecules, cell surface receptors, and extracellular matrix proteins facilitate both tumorigenesis and disease progression to the advanced stages. The well-documented relationship between KLK status and the clinical outcome of cancer patients has led to their identification as promising diagnostic, prognostic, and treatment response monitoring biomarkers for these complex disease entities. The main objective of this review is to summarize the existing knowledge concerning the role of KLKs in prostate, breast, and ovarian cancers and to highlight their continually evolving biomarker capabilities that can provide significant benefits for the management of cancer patients.

Downregulation and Prognostic Performance of MicroRNA 224 Expression in Prostate Cancer

INTRODUCTION The extensive use of prostate-specific antigen as a general prostate cancer biomarker has introduced the hazards of overdiagnosis and overtreatment. Recent studies have revealed the immense biomarker capacity of microRNAs (miRNAs) in prostate cancer. The aim of this study was to analyze the expression pattern of miR-224, a cancer-related miRNA, in prostate tumors and investigate its clinical utility. METHODS Total RNA was isolated from 139 prostate tissue samples. After the polyadenylation of total RNA by poly(A) polymerase, cDNA was synthesized with a suitable poly(T) adapter. miR-224 expression was assessed by quantitative real-time PCR and analyzed with the comparative quantification cycle method, C(q)(2(-ΔΔCq)). We performed comprehensive biostatistical analyses to explore the clinical value of miR-224 in prostate cancer. RESULTS miR-224 expression was significantly downregulated in malignant samples compared with benign samples (P < 0.001). Higher miR-224 expression levels were found in prostate tumors that were less aggressive (P = 0.017) and in an earlier disease stage (P = 0.018). Patients with prostate cancer who were positive for miR-224 had significantly enhanced progression-free survival intervals compared with miR-224-negative patients (P = 0.021). Univariate bootstrap Cox regression confirmed that miR-224 was associated with favorable prognosis (hazard ratio 0.314, P = 0.013); nonetheless, multivariate analysis, adjusted for conventional markers, did not identify miR-224 as an independent prognostic indicator. CONCLUSIONS miR-224 is aberrantly expressed in prostate cancer. Its assessment by cost-effective quantitative molecular methodologies could provide a useful biomarker for prostate cancer.

Kallikrein-related peptidase 13 (KLK13) gene expressional status contributes significantly in the prognosis of primary gastric carcinomas

OBJECTIVES Gastric cancer is a fatal human malignancy with poor prognosis. Modifications in gene expression, including those of the kallikrein-related peptidase family, have been portrayed in gastric carcinogenesis. Given KLK13 involvement in human malignancies, we aimed to uncover its prognostic strength in stomach cancer. DESIGN AND METHODS Quantitative analysis of KLK13 profiles was accomplished in human gastric cancer cells and in a statistically significant sample size of stomach tissue specimens with the development of the highly sensitive real-time PCR methodology. RESULTS Decreased KLK13 expression was demonstrated in cancerous compared with their matching non-malignant pairs (p=0.002) and in poorly differentiated gastric tumors (p=0.029). KLK13-positive patients were shown to live considerably longer (p=0.014) and with low risk of disease recurrences (p=0.043). CONCLUSIONS This is the first study disclosing the possible clinical utility of KLK13 as a new tumor biomarker capable of predicting a favorable outcome for gastric cancer patients.

Quantified KLK15 gene expression levels discriminate prostate cancer from benign tumors and constitute a novel independent predictor of disease progression.

Several transcript variants of the kallikrein‐related peptidase 15 gene (KLK15) have been identified up to now. The classical KLK15 mRNA isoform encodes for a non‐truncated, functional protein. Aberrant KLK15 expression is found in breast, ovarian, and prostate cancers. Our aim in this present study was the specific quantitative expression analysis of the classical KLK15 mRNA transcript in prostate tumors and the examination of its clinical significance in prostate cancer.

Expression analysis and study of the KLK15 mRNA splice variants in prostate cancer and benign prostatic hyperplasia

(Cancer Sci 2010; 101: 693–699)

Targeting kallikrein-related peptidases in prostate cancer

Introduction: Novel therapeutic compounds are needed for prostate cancer (CaP), given the limitations of already used drugs and the diseases mortality, often attributed to castrate resistance. Tissue kallikrein and kallikrein-related peptidases (KLKs) form a family of serine proteases aberrantly expressed and broadly implicated in human malignancies. In CaP, KLKs participate in the promotion of cell proliferation, extracellular matrix degradation, tumour cell invasion and metastasis. Areas covered: This review discusses the different ways of inhibiting, modulating and exploiting KLK activity and/or expression as emerging CaP therapeutics. KLKs are targeted by diverse naturally occurring substances, including proteinaceous inhibitors, low-molecular-weight peptides and Zn2+. Synthetic KLK inhibitors include protein/peptide-based inhibitors and small molecules. A re-engineered serpin-based KLK inhibitor is under evaluation in first-in-human trials as a CaP therapeutic, whereas additional potent and selective KLK inhibitors with relevance to CaP have been synthesized. KLK3-activated pro-drugs have entered Phase I and Phase II clinical trials as therapeutics for prostate tumours. The KLK3-based PROSTVAC® vaccine is evaluated in Phase III clinical trials. Targeting KLK expression via RNA interference methods could represent another promising therapeutic approach for CaP. Expert opinion: Apart from their immense biomarker potential, KLKs also hold promise as the basis of novel CaP therapeutics.

Treatment of PC3 prostate cancer cells with mitoxantrone, etoposide, doxorubicin and carboplatin induces distinct alterations in the expression of kallikreins 5 and 11

Several of the novel kallikrein-related peptidases (tissue kallikreins; KLKs) are emerging new serum and/or tissue biomarkers for prostate cancer (CaP) diagnosis, prognosis and monitoring. In the present research approach, our objective was to investigate the possible alterations in the mRNA expression levels of KLK5 and KLK11 genes in prostate cancer cells PC3 as a response to treatment with mitoxantrone, etoposide, doxorubicin and carboplatin. Viability was assessed with the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay after cell treatment with either mitoxantrone (2 microM), etoposide (20 microM), doxorubicin (1 microM), or carboplatin (15 microM), for 24, 48 and 72 hours. Additionally, trypan blue staining revealed that in PC3 cells all drugs displayed almost the same limited necrotic effects which appeared mainly at 72 hours of treatment. PC3 prostate cancer cells showed a concentration- and time-dependent increased cytotoxicity to the drugs under study which was mainly due to reduction of cell proliferation efficiency. Distinct modulations of KLK5 and KLK11 genes, at the mRNA level, were observed, supporting a drug-dependent cell response. Our experimental data demonstrate that the molecular profile mainly of KLK5 gene may serve as a new potential molecular biomarker predicting treatment response in CaP cells.

Kallikrein-related peptidases (KLKs) in gastrointestinal cancer: mechanistic and clinical aspects.

The human tissue kallikrein (KLK1) and kallikrein-related peptidases (KLKs) are secreted serine proteases with diverse expression patterns and physiological roles in different systems, including the digestive system. The aberrant expression of KLKs in gastrointestinal malignancies as well as their implication in carcinogenesis including cell growth regulation, angiogenesis, invasion, and metastasis, has prompted scientists to investigate their potential as cancer biomarkers. Expression of distinct KLKs is associated with various clinic-pathological parameters of patients with gastric, colorectal, pancreatic, hepatic, and esophageal cancer. Moreover, several KLKs possess significant favourable or unfavourable prognostic value in these human malignancies. Identification of novel diagnostic, prognostic and predictive biomarkers will contribute utmost to clinical decision-making, since early diagnosis of gastrointestinal cancer and early detection of recurrence following surgery are critical for the effective treatment of patients and for a positive clinical outcome. The current review provides a brief overview of the functional role of KLKs in gastric, colorectal, pancreatic, hepatic, and esophageal cancer, and describes the current status of KLKs as potential tumour biomarkers in these human malignancies.

KLK5 gene expression is severely upregulated in androgen-independent prostate cancer cells after treatment with the chemotherapeutic agents docetaxel and mitoxantrone.

Abstract Kallikrein-related peptidases (KLKs), including KLK5, have been proposed as promising biomarkers for prostate cancer diagnosis and prognosis. In the present study, we report that distinct augmentations (up to 6.4-fold) of KLK5 mRNA expressional levels, calculated via quantitative real-time PCR, occur after treatment of DU145 cells with appropriate concentrations, determined by the MTT method, of docetaxel and mitoxantrone. Our data reveal the endogenous need of prostate cancer cells for modified KLK5 expression to cope with the administration of chemotherapeutic drugs. Furthermore, it is proposed that the expression profile of KLK5 could serve as a putative biomarker for monitoring the treatment response in hormone refractory prostate cancer patients.

Long Noncoding RNAs in Digestive System Malignancies: A Novel Class of Cancer Biomarkers and Therapeutic Targets?

High throughput methodologies have revealed the existence of an unexpectedly large number of long noncoding RNAs (lncRNAs). The unconventional role of lncRNAs in gene expression regulation and their broad implication in oncogenic and tumor suppressive pathways have introduced lncRNAs as novel biological tumor markers. The most prominent example of lncRNAs application in routine clinical practice is PCA3, a FDA-approved biomarker for prostate cancer. Regarding digestive system malignancies, the oncogenic HOTAIR is one of the most widely studied lncRNAs in the preclinical level and has already been identified as a potent prognostic marker for major malignancies of the gastrointestinal tract. Here, we provide an overview of recent findings regarding the emerging role of lncRNAs not only as key regulators of cancer initiation and progression in colon, stomach, pancreatic, liver, and esophageal cancers, but also as reliable tumor markers and therapeutic tools. lncRNAs can be easily, rapidly, and cost-effectively determined in tissues, serum, and gastric juice, making them highly versatile analytes. Taking also into consideration the largely unmet clinical need for early diagnosis and more accurate prognostic/predictive markers for gastrointestinal cancer patients, we comment upon the perspectives of lncRNAs as efficient molecular tools that could aid in the clinical management.