The new human tissue kallikrein gene family: structure, function, and association to disease

Quantitative analysis of human kallikrein gene 14 expression in breast tumours indicates association with poor prognosis

KLK14 (formerly known as KLK-L6) is a recently identified member of the human kallikrein gene family. This family harbours several genes aberrantly expressed in various cancers as well as established (PSA/hK3, hK2) and potential (hK6, hK10) cancer markers. Similar to other kallikrein genes, KLK14 was found to be regulated by steroid hormones, particularly androgens and progestins, in breast and ovarian cancer cell lines. Preliminary studies indicated that KLK14 is differentially expressed in breast, ovarian, prostatic and testicular tumours. Given the above, we determined the prognostic significance of KLK14 expression in breast cancer. We studied KLK14 expression in 178 histologically confirmed epithelial breast carcinomas by quantitative reverse transcription-polymerase chain reaction and correlated with clinicopathological variables (tumour stage, grade, histotype etc.) and with outcome (disease-free survival and overall survival), monitored over a median of 76 months. KLK14 mRNA levels ranged from 0 to 1,219 arbitrary units in breast cancer tissues, with a mean+/-s.e. of 136+/-22. An optimal cutoff value of 40.5 arbitrary units was selected, to categorise tumours as KLK14-positive or negative. Higher concentrations of KLK14 mRNA were more frequently found in patients with advanced stage (III) disease (P=0.032). No statistically significant association was found between KLK14 and the other clinicopathological variables. KLK14 overexpression was found to be a significant predictor of decreased disease-free survival (hazard ratio of 2.31, P=0.001) and overall survival (hazard ratio of 2.21, P=0.005). Cox multivariate analysis indicated that KLK14 was an independent prognostic indicator of disease-free survival and overall survival. KLK14 also has independent prognostic value in subgroups of patients with a tumour size </=2 cm and positive nodal, oestrogen receptor and progestin receptor status. We conclude that KLK14 expression, as assessed by quantitative reverse transcription-polymerase chain reaction, is an independent marker of unfavourable prognosis for breast cancer.

Immunofluorometric quantitation and histochemical localisation of kallikrein 6 protein in ovarian cancer tissue: a new independent unfavourable prognostic biomarker

Human kallikrein 6 protein is a newly discovered human kallikrein. We determined the amount of human kallikrein 6 in extracts of 182 ovarian tumours and correlated specific activity (ng hK6 mg(-1) total protein) with clinicopathological variables documented at the time of surgical excision and with outcome (progression free survival, overall survival) monitored over a median interval of 62 months. Thirty per cent of the tumours were positive for human kallikrein 6 (>35 ng hK6 mg(-1) total protein). Human kallikrein 6-specific immunohistochemical staining of four ovarian tissues that included benign, borderline and malignant lesions indicated a cytoplasmic location of human kallikrein 6 in tumour cells of epithelial origin, although the intensity of staining was variable. Tumour human kallikrein 6 (ng hK6 mg(-1) total protein) was higher in late stage disease, serous histotype, residual tumour >1 cm and suboptimal debulking (>1 cm) (P<0.05). Univariate analysis revealed that patients with tumour human kallikrein 6 positive specific activity were more likely to suffer progressive disease and to die (hazard ratio 1.71 (P=0.015) and 1.88 (P=0.022), respectively). Survival curves demonstrated the same (P=0.013 and 0.019, respectively). Multivariate analysis revealed that human kallikrein 6 positivity was retained as an independent prognostic variable in several subgroups of patients, namely those with (low) grade I and II tumours (hazard ratio progression free survival 4.3 (P=0.027) and overall survival 4.1 (P=0.023)) and those with optimal debulking (hazard ratio progression free survival 3.8 (P=0.019) and overall survival 5.6 (P=0.011)). We conclude that tumour kallikrein 6 protein levels have utility as an independent adverse prognostic marker in a subgroup of ovarian cancer patients with otherwise apparently good prognosis.

Higher expression of human kallikrein 10 in breast cancer tissue predicts tamoxifen resistance

The human tissue kallikreins are secreted serine proteases, encoded by a group of homologous genes clustered in tandem on chromosome 19q13.3-4. Human kallikrein 6 and human kallikrein 10 are two new members of this family. Recently, we developed highly sensitive and specific immunofluorometric assays for human kallikrein 6 and human kallikrein 10, which allow for their quantification in tissue extracts and biological fluids. Both human kallikrein 6 and human kallikrein 10 are found to be down-regulated in breast cancer cell lines, suggesting that they may be involved in breast cancer pathogenesis and progression. In this study, we investigated the potential value of human kallikrein 6 and human kallikrein 10 as prognostic and predictive factors in breast cancer. We quantified human kallikrein 6 and human kallikrein 10 protein levels in 749 breast tumour cytosolic extracts and correlated this data with various clinicopathological variables and patient outcomes. Human kallikrein 6 and human kallikrein 10 are positively correlated with each other. Higher human kallikrein 6 and human kallikrein 10 protein levels are associated with younger age, pre-menopausal, status and tumours which are negative for oestrogen and progesterone receptors. No correlation was found between human kallikrein 6 and human kallikrein 10 levels and tumour size, grade, and nodal status. Survival analysis showed that neither human kallikrein 6 nor human kallikrein 10 are related to the rate of relapse-free and overall survival. In the analysis with respect to response to tamoxifen therapy, although human kallikrein 6 levels were not associated with tamoxifen responsiveness, higher levels of human kallikrein 10 were significantly associated with a poor response rate. This association remained significant in the multivariate analysis. Furthermore, higher human kallikrein 10 levels were significantly related with a short progression-free and post-relapse overall survival after start of tamoxifen treatment for advanced disease. Taken together, our results suggest that although human kallikrein 6 and human kallikrein 10 are not prognostic markers for breast cancer, human kallikrein 10 is an independent predictive marker for response of tamoxifen therapy.

Immunohistochemical localization of human kallikreins 6 and 10 in pancreatic islets

Tissue kallikreins are thought to be present in the pancreatic islets of Langerhans and to aid in the conversion of proinsulin to insulin. In recent immunohistochemical studies, we observed strong staining of the newly identified human kallikreins 6 and 10 (hK6 and hK10) in the islets of Langerhans. Here, we examine hK6 and hK10 immunoexpression in different types of islet cells of the endocrine pancreas, in order to obtain clues for hK6 and hK10 function in these cells. Ten cases of normal pancreatic tissue, two cases of nesidioblastosis, five insulin-producing tumours and one case of multiple endocrine neoplasia 1 syndrome, containing an insulin-, a somatostatin- and several glucagon-producing tumours, as well as tiny foci of endocrine dysplasia with different predominance of the secreted hormones (mainly glucagon and pancreatic polypeptide) were included in the study. A streptavidin--biotin--peroxidase and an alkaline phosphatase protocol, as well as a sequential immunoenzymatic double staining method were performed, using specific antibodies against hK6, hK10, insulin, glucagon, somatostatin, pancreatic polypeptide, and serotonin. hK6 and hK10 immunoexpression was observed in the islets of Langerhans, including the pancreatic polypeptide-rich islets, in the normal pancreas. Scattered hK6 and hK10 positive cells were localized in relationship with pancreatic acinar cells. In the exocrine pancreas, a cytoplasmic and/or brush border hK6 and hK10 immunoexpression was observed in the median and small sized pancreatic ducts, while the acinar cells were negative. Foci of nesidioblastosis and endocrine dysplasia expressed both kallikreins. hK6 and hK10 were also strongly and diffusely expressed throughout all insulin-, glucagon- and somatostatin-producing tumours. The double staining method revealed co-localization of each hormone and hK6/hK10 respectively, in the same cellular population, in the normal as well as in the diseased pancreas. Our results support the view that hK6 and hK10 may be involved in insulin and other pancreatic hormone processing and/or secretion, as well as in physiological functions related to the endocrine pancreas.

Human kallikrein gene 13 (KLK13) expression by quantitative RT-PCR: an independent indicator of favourable prognosis in breast cancer

Kallikreins are a group of serine proteases with diverse physiological functions. KLK13 (previously known as KLK-L4) is a novel kallikrein gene located on chromosome 19q13.4 and shares a high degree of homology with other kallikrein family members. Many kallikrein genes were found to be differentially expressed in various malignancies, and their regulation is controlled by steroid hormones in prostate and breast cancer cell lines. We studied the expression of KLK13 by quantitative reverse transcriptase-polymerase chain reaction in 173 patients with epithelial breast carcinoma. An optimal cutoff point equal to the 40th percentile was defined, based on the ability of KLK13 to predict disease-free survival. KLK13 values were then associated with other established prognostic factors and with disease-free survival and overall survival. Higher positivity for KLK13 expression was found in older, oestrogen receptor positive patients. In univariate analysis, KLK13 expression is a significant predictor of improved disease-free survival and overall survival (P<0.001 and P=0.009, respectively). Cox multivariate analysis indicated that KLK13 was an independent prognostic variable in the subgroups of patients with Grade I-II tumours and in patients who were oestrogen receptor and progesterone receptor positive, and node positive. Hazard ratios derived from Cox analysis, related to disease-free survival and overall survival were 0.22 (P=0.001) and 0.24 (P=0.008), respectively, for the Grade I-II group; 0.36 (P=0.008) and 0.44 (P=0.038), respectively, for the node positive group and 0.36 (P=0.008) and 0.18 (P=0.008), respectively, for the oestrogen receptor positive group. The adjusted hazard ratio for progesterone receptor positive patients for disease-free survival was 0.25 (P=0.012). For patients in the node positive and oestrogen receptor positive subgroup (n=51) the adjusted hazard ratio was 0.25 (P=0.006) and for the node positive and progesterone receptor positive subgroup (n=46) the hazard ratio was 0.24 (P=0.008). Taken together, these data suggest that higher KLK13 expression in these subgroups of breast cancer patients is associated with an approximately 55 to 80% reduction in the risk of relapse or death. We conclude that KLK13 expression, as assessed by quantitative reverse transcriptase-polymerase chain reaction, is an independent favourable prognostic marker for breast carcinoma.