Methylation of cystatin M promoter is associated with unfavorable prognosis in operable breast cancer

The methylation status of cystatin M (CST6) gene in breast tumors was investigated and its prognostic significance as a novel breast cancer biomarker was evaluated. Using methylation-specific PCR (MSP), CST6 promoter methylation was examined in 134 formalin fixed paraffin-embedded tissues (FFPEs): 10 pairs of breast tumors and their surrounding normal tissues, 10 breast fibroadenomas, 11 normal breast tissues and 93 breast tumors. Methylation of CST6 promoter was observed in 2/21 (9.5%) noncancerous breast tissues, 1/10 (10%) benign breast tumors (fibroadenomas) and 52 (55.9%) operable breast cancer tumor samples. CST6 was rarely methylated in the normal tissue surrounding the tumor (10%). During the follow-up period, 24 (25.8%) patients relapsed and 19 (20.4%) died. CST6 methylation was detected in 19 (79.2%) of patients who relapsed and in 15 (78.9%) of patients who died. Disease-free-interval (DFI) and overall survival (OS) were significantly associated with CST6 promoter methylation (p=0.004 and p=0.001 respectively). Multivariate analysis revealed that CST6 methylation is an independent prognostic factor for DFI (HR=3.484; 95% CI: 1.155-10.511; p=0.027). and OS (HR=9.190; 95% CI: 1.989-42.454; p=0.004). CST6 promoter methylation status in tumor cells seems to provide important prognostic information in operable breast cancer and merits to be further evaluated and validated in a larger cohort of patients.

Functional roles of human kallikrein-related peptidases

Kallikrein-related peptidases constitute a single family of 15 (chymo)trypsin-like proteases (KLK1-15) with pleiotropic physiological roles. Aberrant regulation of KLKs has been associated with diverse diseases such as hypertension, renal dysfunction, skin disorders, inflammation, neurodegeneration, and cancer. Recent studies suggested that coordinated activation and regulation of KLK activity are achieved via a complex network of interactions referred to as the "KLK activome." However, it remains to be validated whether these hypothetical KLK activation cascade pathways are operative in vivo. In addition, KLKs have emerged as versatile signaling molecules. In summary, KLKs represent attractive biomarkers for clinical applications and potential therapeutic targets for common human pathologies.

Down-regulation of dicer expression in ovarian cancer tissues

OBJECTIVES

Although numerous recent studies have focused on analyses of microRNA expression profiles in cancer cells, the expression patterns of the enzymes responsible for the generation of miRNAs remains largely unexplored. The purpose of this study was to investigate whether Dicer mRNA expression is altered during progression of ovarian cancer.

DESIGN AND METHODS

Total RNA was extracted from ovarian tissue specimens (normal, benign and malignant tumors). The expression of Dicer was analyzed by semi-quantitative RT-PCR.

RESULTS

We analyzed a total of 34 ovarian tissue samples and found that Dicer mRNA expression is down-regulated in the majority of ovarian tumors when compared to normal tissues.

CONCLUSIONS

Our results suggest that the levels of Dicer mRNA should be evaluated as a potential new candidate biomarker for ovarian cancer.

Emerging roles of microRNAs as molecular switches in the integrated circuit of the cancer cell

Transformation of normal cells into malignant tumors requires the acquisition of six hallmark traits, e.g., self-sufficiency in growth signals, insensitivity to antigrowth signals and self-renewal, evasion of apoptosis, limitless replication potential, angiogenesis, invasion, and metastasis, which are common to all cancers (Hanahan and Weinberg 2000). These new cellular traits evolve from defects in major regulatory microcircuits that are fundamental for normal homeostasis. The discovery of microRNAs (miRNAs) as a new class of small non-protein-coding RNAs that control gene expression post-transcriptionally by binding to various mRNA targets suggests that these tiny RNA molecules likely act as molecular switches in the extensive regulatory web that involves thousands of transcripts. Most importantly, accumulating evidence suggests that numerous microRNAs are aberrantly expressed in human cancers. In this review, we discuss the emergent roles of microRNAs as switches that function to turn on/off known cellular microcircuits. We outline recent compelling evidence that deregulated microRNA-mediated control of cellular microcircuits cooperates with other well-established regulatory mechanisms to confer the hallmark traits of the cancer cell. Furthermore, these exciting insights into aberrant microRNA control in cancer-associated circuits may be exploited for cancer therapies that will target deregulated miRNA switches.

Novel splice variants of prostate-specific antigen and applications in diagnosis of prostate cancer

OBJECTIVES

We aimed to identify novel splice variants of prostate-specific antigen/or human kallikrein 3 (PSA/KLK3), the most widely used serum biomarker for case-finding, screening and monitoring of prostate cancer.

DESIGN AND METHODS

The full-length sequences of splice variants were assembled as contigs from human ESTs that displayed homology to the cDNA sequence encoding PSA. Expression of variants in clinical samples was analyzed by semi-quantitative RT-PCR.

RESULTS

EST database mining led to the identification of seven previously unidentified splice variants encoding PSA-like proteins that are predicted to contain epitope sequences recognized by PSA-specific antibodies, therefore, expression of these isoforms may affect the amount of total PSA measured by established immunoassays. Analysis of the differential expression profile of isoform PSA-SV5 in patients with benign prostate hyperplasia and prostate cancer showed that it is specifically expressed in prostate cancers.

CONCLUSIONS

A novel splice variant of PSA was identified, PSA-SV5, that may be exploited in clinical diagnosis to distinguish prostate cancer from benign prostate hyperplasia.

Tissue kallikrein proteolytic cascade pathways in normal physiology and cancer

Human tissue kallikreins (KLKs or kallikrein-related peptidases) are a subgroup of extracellular serine proteases that act on a wide variety of physiological substrates, while they display aberrant expression patterns in certain types of cancer. Differential expression patterns lead to the exploitation of these proteins as new cancer biomarkers for hormone-dependent malignancies, in particular. The prostate-specific antigen or kallikrein-related peptidase 3 (PSA/KLK3) is an established tumor marker for the diagnosis and monitoring of prostate cancer. It is well documented that specific KLK genes are co-expressed in tissues and in various pathologies suggesting their participation in complex proteolytic cascades. Here, we review the currently established knowledge on the involvement of KLK proteolytic cascades in the regulation of physiological and pathological processes in prostate tissue and in skin. It is well established that the activity of KLKs is often regulated by auto-activation and subsequent autolytic internal cleavage leading to enzymatic inactivation, as well as by inhibitory serpins or by allosteric inhibition by zinc ions. Redistribution of zinc ions and alterations in their concentration due to physiological or pathological reasons activates specific KLKs initiating the kallikrein cascade(s). Recent studies on kallikrein substrate specificity allowed for the construction of a kallikrein interaction network involved in semen liquefaction and prostate cancer, as well as in skin pathologies, such as skin desquamation, psoriasis and cancer. Furthermore, we discuss the crosstalks between known proteolytic pathways and the kallikrein cascades, with emphasis on the activation of plasmin and its implications in prostate cancer. These findings may have clinical implications for the underlying molecular mechanism and management of cancer and other disorders in which KLK activity is elevated.

Development of an immunofluorometric assay for human kallikrein 15 (KLK15) and identification of KLK15 in tissues and biological fluids

BACKGROUND

Human kallikrein 15 (KLK15) may have some utility as a prostate, ovarian, and breast cancer biomarker, based on previous studies, which examined mRNA levels of KLK15. The aim of this study was to develop analytical technology for human kallikrein 15, including recombinant protein, specific antibodies, and a sensitive and specific ELISA immunoassay. The assay was then used to examine levels of KLK15 in tissues and biological fluids.

METHODS

We produced human, recombinant pro-KLK15 in HEK 293 cells. Recombinant KLK15 was purified with various chromatographic steps and used to immunize rabbits and mice for production of KLK15 polyclonal antibodies. We used these antibodies to develop a highly sensitive and specific KLK15 immunoassay and to study KLK15 expression in various tissues and biological fluids.

RESULTS

Large amounts of pure, recombinant KLK15 have been produced and characterized. KLK15 mouse and rabbit polyclonal antibodies have been employed for development of a KLK15 immunoassay. This assay has a lower detection limit of 0.05 microg/L, and no cross-reactivity with any of the other fourteen kallikreins. Using this assay, KLK15 was detected in prostate, colon, and thyroid tissues, as well as in breast milk and seminal plasma.

CONCLUSIONS

The KLK15 reagents developed here will allow for analysis of KLK15 protein expression levels in tissues and biological fluids, both normal and cancerous. This will expand upon previously characterized tissue KLK15 mRNA expression studies which suggested that KLK15 might be useful as a biomarker for breast, ovarian, and prostate cancer. KLK15 is another serine protease that is produced in prostate and other tissues and is secreted in seminal plasma and other fluids. Its physiological function needs to be further elucidated.

A potential role for multiple tissue kallikrein serine proteases in epidermal desquamation

Desquamation of the stratum corneum is a serine protease-dependent process. Two members of the human tissue kallikrein (KLK) family of (chymo)tryptic-like serine proteases, KLK5 and KLK7, are implicated in desquamation by digestion of (corneo)desmosomes and inhibition by desquamation-related serine protease inhibitors (SPIs). However, the epidermal localization and specificity of additional KLKs also supports a role for these enzymes in desquamation. This study aims to delineate the probable contribution of KLK1, KLK5, KLK6, KLK13, and KLK14 to desquamation by examining their interactions, in vitro, with: 1) colocalized SPI, lympho-epithelial Kazal-type-related inhibitor (LEKTI, four recombinant fragments containing inhibitory domains 1-6 (rLEKTI(1-6)), domains 6-8 and partial domain 9 (rLEKTI(6-9')), domains 9-12 (rLEKTI(9-12)), and domains 12-15 (rLEKTI(12-15)), secretory leukocyte protease inhibitor, and elafin and 2) their ability to digest the (corneo)desmosomal cadherin, desmoglein 1. KLK1 was not inhibited by any SPI tested. KLK5, KLK6, KLK13, and KLK14 were potently inhibited by rLEKTI(1-6), rLEKTI(6-9'), and rLEKTI(9-12) with Ki values in the range of 2.3-28.4 nm, 6.1-221 nm, and 2.7-416 nm for each respective fragment. Only KLK5 was inhibited by rLEKTI(12-15) (Ki = 21.8 nm). No KLK was inhibited by secretory leukocyte protease inhibitor or elafin. Apart from KLK13, all KLKs digested the ectodomain of desmoglein 1 within cadherin repeats, Ca2+ binding sites, or in the juxtamembrane region. Our study indicates that multiple KLKs may participate in desquamation through cleavage of desmoglein 1 and regulation by LEKTI. These findings may have clinical implications for the treatment of skin disorders in which KLK activity is elevated.

Evaluation of ER, PR, MIB-1, pS2, and nuclear grade in FNA specimens of cT1 breast carcinomas: clinicopathological correlation

Objectives were to determine oestrogen (ER), progesterone receptors (PR), and antigen related to ER (pS2) and to characterize their relationship with the cellular proliferation marker MIB-1 and the nuclear grade (NG) of the cancer cells, using fine-needle aspirates (FNA), as well as the evaluation of their clinical usefulness. The expression of ER, PR, pS2, and MIB-1 was preoperatively detected by immunocytochemistry in FNAs of 70 patients with breast adenocarcinoma and clinical tumor size up to 2 cm. The NG of the tumor cells was also assessed in these samples. We analyzed whether there was any correlation between these biocytologic markers and the invasion of ipsillateral axillary lymph nodes (LN), which were histologically identified after standard surgical treatment in each case. Of the 70 patients 50, 42.85, 50, and 41.42% were positive for ER, PR, pS2, and MIB-1, respectively. Only NG alone was strongly related to the invasion of the LN (P < 0.001). All the patients with NG1 (100%) tumors presented free LN, whereas the majority of those with NG3 (72.72%) had invaded LN (P < 0.001). Patients (14.28%) with NG1 expressed MIB-1, 85.71% ER or PR, and 71.42% pS2. Among the MIB-1-positive tumors a high proportion of NG3 (65.51%) was observed. This finding underlined a relationship between MIB-1 and NG (P < 0.05), identifying an aggressive cancer type. Remarkably 93.33% of the patients with positive MIB-1 and invaded axilla had NG3, whereas 66.66% of them expressed ER or PR and 40% pS2. The findings of the present prospective, multivariate study indicate that NG of the tumor cells, obtained from the preoperative FNAs of breast cancer patients, is a strong predictive marker for the axillary status and in parallel with MIB-1 expression can with sufficient accuracy be of clinical utility. ER, PR, or pS2 on the other hand did not show any relation to the LN status and were not dependent to NG or MIB-1.

The epigenetic basis for the aberrant expression of kallikreins in human cancers

The tissue kallikrein gene family consists of 15 genes tandemly arranged on human chromosome 19q13.4. Most kallikrein genes are characterized by aberrant expression patterns in various human cancers, a feature that makes them ideal cancer biomarkers. In the present study, we investigated the effect of the epigenetic drug compound 5-aza-2'-deoxycytidine on the expression of downregulated kallikrein genes in prostate, breast, and ovarian cancer cell lines. Reactivation of multiple kallikrein genes was observed, although some of these genes do not contain CpG islands in their genomic sequence. Epigenetic regulation provides a new mechanism for the pharmacological modulation of kallikreins in human cancers with putative therapeutic implications.

Preoperative prediction of the axillary lymph nodes status in patients with breast cancer

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Background: We developed a preoperative score-system (S) and evaluated prospectively its predictive value for the axillary(a) status of patients (p) with breast cancer. Our aim was to select preoperatively (p) with negative axilla, who could possibly avoid the standard (a) surgery. (S) uses preoperative clinical, epidemiological and immunocytological data, obtained from the FNA-smears of (p)‘ tumors, and attempts to guide the choice of (a) treatment, as an alternative to the method of sentinel lymph node. Methods: (S) is calculated by adding the preoperative values of clinical tumor size, (p) age, nuclear grade (NG), type of the cancer cells and the immunocytochemical positiveness of the biomarkers p53, HER2 and MIB1. Values range from 1–4 for size (1–10, 11–15, 16–20, 20–30 mm), 1 to 4 for age (70 and over, 51–69, 41–50, 40 years or less), 1–3 for NG1–3, 1–2 for type of cancer cells (lobular, ductal) respectively and 0–3 for the expression (1 point for every positive biomarker) or absence (0) of p53, HER2 and MIB1 in the FNA of the primary tumors of the (p). (S) ranges from 4 to 16.We applied (S) to 224 (p), with clinically negative axilla. These (p) underwent modified radical mastectomy or lumpectomy and standard (a) dissection level I and II. The number of the infiltrated nodes was identified in each case. Results: (S) of 4 - 8 (57 patients, group 1) identify (p) with free nodes ( node positive rate 0%). (S) of 9 and 10 (67 patients, group 2) carry an average node positive rate of 65,67%, of which 31,34% involves the invasion of 1 node, 23,88% of 2–3 and 10,44% of 4 or more nodes (P < 0.001, group 1 versus group 2). (S) of 11 and more (100 patients, group 3) identify (p) with an average node positive rate of 83%, of which 55% involves the invasion of 4 or more nodes (P < 0.001, group 3 versus group 1). (S) allows the separation of (p) into two (a) management groups. Group 1 are those (p), who possibly have free lymph nodes and therefore may need no (a) surgery at all, whereas group 2 and 3 may be considered for standard (a) dissection, because they present with increased possibility infiltrated nodes. Conclusion: (S) was studied to aid the selection of (p) towards reasonable (a) treatment choices for the benefit of (p). (S) might serve as a guideline in the clinical practice to reduce the postoperative morbidity of the breast cancer (p).

No significant financial relationships to disclose.

Human tissue kallikrein 5 is a member of a proteolytic cascade pathway involved in seminal clot liquefaction and potentially in prostate cancer progression

Human tissue kallikreins (hKs) are a family of fifteen serine proteases. Several lines of evidence suggest that hKs participate in proteolytic cascade pathways. Human kallikrein 5 (hK5) has trypsin-like activity, is able to self-activate, and is co-expressed in various tissues with other hKs. In this study, we examined the ability of hK5 to activate other hKs. By using synthetic heptapeptides that encompass the activation site of each kallikrein and recombinant pro-hKs, we demonstrated that hK5 is able to activate pro-hK2 and pro-hK3. We then showed that, following their activation, hK5 can internally cleave and deactivate hK2 and hK3. Given the predominant expression of hK2 and hK3 in the prostate, we examined the pathophysiological role of hK5 in this tissue. We studied the regulation of hK5 activity by cations (Zn2+, Ca2+, Mg2+, Na2+, and K+) and citrate and showed that Zn can efficiently inhibit hK5 activity at levels well below its normal concentration in the prostate. We also show that hK5 can degrade semenogelins I and II, the major components of the seminal clot. Semenogelins can reverse the inhibition of hK5 by Zn2+, providing a novel regulatory mechanism of its serine protease activity. hK5 is also able to internally cleave insulin-like growth factor-binding proteins 1, 2, 3, 4, and 5, but not 6, suggesting that it might be involved in prostate cancer progression through growth factor regulation. Our results uncover a kallikrein proteolytic cascade pathway in the prostate that participates in seminal clot liquefaction and probably in prostate cancer progression.

Multiple mechanisms underlie the aberrant expression of the human kallikrein 6 gene in breast cancer

Human kallikrein 6 (KLK6) was identified based on its transient upregulation in a primary breast tumor and its subsequent silencing in a metastatic tumor from the same patient. The molecular mechanism(s) underlying the deregulated expression of KLK6 during cancer progression are currently unknown. Here, we provide evidence that aberrant expression of KLK6 is regulated at the level of transcription by multiple cooperating mechanisms. KLK6 can be reactivated in non-expressing breast cancer cells by treatment with 5-aza-2'-deoxycytidine (5-aza-dC), a compound causing DNA demethylation. Trichostatin A (TSA), an inhibitor of histone deacetylases, resulted in moderate induction of KLK6 only in MDA-MB-231 cells. However, combined 5-aza-dC/TSA treatment resulted in synergistic activation of KLK6. We show that KLK6 inactivation is associated with hypermethylation of specific CpG dinucleotides located in the KLK6 proximal promoter and overexpression with complete demethylation. These results indicate a causal role of DNA methylation and chromatin structure in cancer-associated loss of KLK6 expression. In some breast cancer cell lines, KLK6 expression could be restored by the vitamin D3 analog EB1089. Our data indicate that transcriptional deregulation of KLK6 in cancer cells during breast cancer progression is complex and certainly not uniform in different tumors, involving epigenetic mechanisms as well as pathways regulated by nuclear receptors. This allows for the pharmacological modulation of KLK6 with potential therapeutic implications.

A comprehensive nomenclature for serine proteases with homology to tissue kallikreins

The human kallikrein locus on chromosome 19q13.3-13.4 contains kallikrein 1--the tissue kallikrein--and 14 related serine proteases. Recent investigations into their function and evolution have indicated that the present nomenclature for these proteins is inadequate or insufficient. Here we present a new nomenclature in which proteins without proven kininogenase activity are denoted kallikrein-related peptidase. Names are also given to the unique rodent proteins that are closely related to kallikrein 1.

Downregulation of human kallikrein 10 (KLK10/NES1) by CpG island hypermethylation in breast, ovarian and prostate cancers

OBJECTIVE

The human kallikrein 10 (KLK10)/normal epithelial cell-specific-1 (NES1) gene is highly expressed in normal mammary, ovary and prostate cells, but its expression is dramatically decreased in cancer cell lines. Recently, it has been shown that CpG island hypermethylation of the KLK10 gene is responsible for the tumor-specific loss of KLK10 gene expression in certain breast cancer cell lines.

METHOD

We examined the role of CpG island hypermethylation in the tumor-specific loss of KLK10 expression in breast, ovarian and prostate cancers. We treated cells with the demethylating agent 5-aza-2'-deoxycytidine (dC) and monitored changes in KLK10 mRNA by RT-PCR and secreted hK10 protein expression by ELISA. The following cell lines were used: MDA-MB-231, MDA-MB-468, MCF-7, ZR-75-1, T-47D and BT-474 (breast); BG-1, MDAH-2774, HTB-75, HTB-161, PA-1 and ES-2 (ovary), and LNCaP and PC-3 (prostate).

RESULTS

Upregulation of KLK10 mRNA levels, which was accompanied by an increase in secreted hK10 protein concentration, was observed for a subset of breast, ovarian, and prostate tumor cell lines after 5-aza-2'-dC. Genomic sequencing of sodium-bisulfite-treated DNA demonstrated that CpG sites within the KLK10 gene exon 3 were highly methylated. Hypermethylation of exon 3 CpG regions was also detected in primary ovarian cancers.

CONCLUSION

These data suggest that CpG island hypermethylation plays an important role in the downregulation of kallikrein 10 mRNA and protein expression, but it cannot explain the pattern of expression of this gene in all cell lines or tissue tested.

Human kallikrein 4: quantitative study in tissues and evidence for its secretion into biological fluids

BACKGROUND

Human kallikrein 4 (hK4) is a proteolytic enzyme belonging to the tissue kallikrein family of serine proteases. Previous tissue expression studies have demonstrated highest KLK4 mRNA expression in prostatic tissue, but there has been only limited evidence for the presence of hK4 protein in prostate and other tissues and in corresponding biological secretions.

METHODS

To investigate the concentrations of hK4 in tissues and biological fluids, we developed a new hK4-specific sandwich-type immunoassay using a monoclonal antibody as the capture reagent.

RESULTS

The assay has a detection limit of 0.02 microg/L and <0.1% cross-reactivity toward any of the other 14 human kallikreins. Twelve of 40 tissue extracts prepared from various human tissues contained detectable hK4 concentrations (0.68-7143 ng/g of total protein), with healthy prostate tissue containing the highest amount of hK4. Examination of 16 malignant and 18 benign prostate tissues revealed no significant differences in hK4 protein content, and the tissues contained a wide range of values (benign, <0.02 to 801 ng/g; malignant, <0.02 to 824 ng/g). Among the biological fluids tested, seminal plasma and urine contained widely varying amounts of hK4; concentrations in 54 urine samples were <0.02 to 2.6 microg/L, whereas concentrations in 58 seminal plasma samples were 0.2-202 microg/L. Affinity purification of hK4 from seminal plasma and subsequent mass spectrometry demonstrated the secreted nature of hK4 in seminal plasma.

CONCLUSIONS

hK4 is found primarily in prostate tissue and is secreted in seminal plasma. Its value as a novel prostatic biomarker needs to be defined further.

Human kallikrein 6 degrades extracellular matrix proteins and may enhance the metastatic potential of tumour cells

Human kallikrein 6 (hK6), a trypsin-like serine protease, is a newly identified member of the kallikrein gene family. Its involvement in inflammatory CNS lesions and in demyelination has been reported. Recent work has suggested that expression of this enzyme is significantly elevated in patients with ovarian cancer. We have identified many tumour cell lines that secrete hK6, but its physiological role is unknown. Here, we try to unveil the role of this kallikrein in the metastasis and invasion of tumour cells. We demonstrate that purified human recombinant hK6 can cleave gelatin in zymography and can efficiently degrade high-molecular-weight extracellular matrix proteins such as fibronectin, laminin, vitronectin and collagen. In Boyden chamber assays, we found that tumour cells treated with a neutralizing hK6 antibody migrate less than control cells. We conclude that hK6 might play a role in the invasion and metastasis of tumour cells and may be a candidate therapeutic target.

Biochemical and enzymatic characterization of human kallikrein 5 (hK5), a novel serine protease potentially involved in cancer progression

Human kallikrein 5 (KLK5) is a member of the human kallikrein gene family of serine proteases. Preliminary results indicate that the protein, hK5, may be a potential serological marker for breast and ovarian cancer. Other studies implicate hK5 with skin desquamation and skin diseases. To gain further insights on hK5 physiological functions, we studied its substrate specificity, the regulation of its activity by various inhibitors, and identified candidate physiological substrates. After producing and purifying recombinant hK5 in yeast, we determined the k(cat)/K(m) ratio of the fluorogenic substrates Gly-Pro-Arg-AMC and Gly-Pro-Lys-AMC, and showed that it has trypsin-like activity with strong preference for Arg over Lys in the P1 position. The serpins alpha(2)-antiplasmin and antithrombin were able to inhibit hK5 with an inhibition constant (k(+2)/K(i)) of 1.0 x 10(-) (2)and 4.2 x 10(-4) m(-1) min(-1), respectively. No inhibition was observed with the serpins alpha(1)-antitrypsin and alpha(1)-antichymotrypsin, although alpha(2)-macroglobulin partially inhibited hK5 at high concentrations. We also demonstrated that hK5 can efficiently digest the extracellular matrix components, collagens type I, II, III, and IV, fibronectin, and laminin. Furthermore, our results suggest that hK5 can potentially release (a) angiostatin 4.5 from plasminogen, (b) "cystatin-like domain 3" from low molecular weight kininogen, and (c) fibrinopeptide B and peptide beta15-42 from the Bbeta chain of fibrinogen. hK5 could also play a role in the regulation of the binding of plasminogen activator inhibitor 1 to vitronectin. Our findings suggest that hK5 may be implicated in tumor progression, particularly in invasion and angiogenesis, and may represent a novel therapeutic target.

Cloning and characterization of novel isoforms of the human kallikrein 6 gene

Human kallikrein 6 (protease M/zyme/neurosin) was originally identified based on its aberrant expression in tumor cells and is considered a biomarker for ovarian cancer. Here, we describe the identification, cloning, and tissue expression of three novel transcript variants of the KLK6 gene that encode for wild-type kallikrein 6. Contrary to the classical form, transcript variants contain one untranslated exon, exploit intronic sequences, and are likely products of alternative promoters. In addition, we cloned splice variants 2 and 3 produced by splicing out exons 3 and 4, respectively. Given the potential diagnostic applications of kallikrein 6 at both the mRNA and protein levels, we developed a duplex RT-PCR, in order to differentially detect and quantitate mRNA species corresponding to splice variants. We show that in normal mammary epithelial cells and mammary tumor cell lines that overexpress the KLK6 gene, splice variants account for approximately 10-20% of all mRNA species.

Human kallikrein 6 activity is regulated via an autoproteolytic mechanism of activation/inactivation

Human kallikrein 6 (protease M/zyme/neurosin) is a serine protease that has been suggested to be a serum biomarker for ovarian cancer and may also be involved in pathologies of the CNS. The precursor form of human kallikrein 6 (pro-hK6) was overexpressed in Pichia pastoris and found to be autoprocessed to an active but unstable mature enzyme that subsequently yielded the inactive, self-cleavage product, hK6 (D81-K244). Site-directed mutagenesis was used to investigate the basis for the intrinsic catalytic activity and the activation mechanism of pro-hK6. A single substitution R80 --> Q stabilized the activity of the mature enzyme, while substitution of the active site serine (S197 --> A) resulted in complete loss of hK6 proteolytic activity and facilitated protein production. Our data suggest that the enzymatic activity of hK6 is regulated by an autoactivation/autoinactivation mechanism. Mature hK6 displayed a trypsin-like activity against synthetic substrates and human plasminogen was identified as a putative physiological substrate for hK6, as specific cleavage at the plasminogen internal bond S460-V461 resulted in the generation of angiostatin, an endogenous inhibitor of angiogenesis and metastatic growth.

Cystatin M suppresses the malignant phenotype of human MDA-MB-435S cells

Proteases are involved in many aspects of tumor progression, including cell survival and proliferation, escape from immune surveillance, cell adhesion and migration, remodeling and invasion of the extracellular matrix. Several lysosomal cysteine proteases have been cloned and shown to be overexpressed in cancer; yet, despite the great potential for development of novel therapeutics, we still know little about the regulation of their proteolytic activity. Cystatins such as cystatin M are potent endogenous protein inhibitors of lysosomal cysteine proteases. Cystatin M is expressed in normal and premalignant human epithelial cells, but not in many cancer cell lines. Here, we examined the effects of cystatin M expression on malignant properties of human breast carcinoma MDA-MB-435S cells. Cystatin M was found to significantly reduce in vitro: cell proliferation, migration, Matrigel invasion, and adhesion to endothelial cells. Reduction of cell proliferation and adhesion to an endothelial cell monolayer were both independent of the inhibition of lysosomal cysteine proteases. In contrast, cell migration and matrix invasion seemed to rely on lysosomal cysteine proteases, as both recombinant cystatin M and E64 were able to block these processes. This study provides the first evidence that cystatin M may play important roles in safeguarding against human breast cancer.

Characterization of the enzymatic activity of human kallikrein 6: Autoactivation, substrate specificity, and regulation by inhibitors

Human kallikrein 6 (hK6) is a trypsin-like serine protease, member of the human kallikrein gene family. Studies suggested a potential involvement of hK6 in the development and progression of Alzheimer's disease. The serum levels of hK6 might be used as a biomarker for ovarian cancer. To gain insights into the physiological role of this enzyme, we sought to determine its substrate specificity and its interactions with various inhibitors. We produced the proform of hK6 and showed that this enzyme was able to autoactivate, as well as proteolyse itself, leading to inactivation. Kinetic studies indicated that hK6 cleaved with much higher efficiency after Arg than Lys and with a preference for Ser or Pro in the P2 position. The efficient degradation of fibrinogen and collagen types I and IV by hK6 indicated that this kallikrein might play a role in tissue remodeling and/or tumor invasion and metastasis. We also demonstrated proteolysis of amyloid precursor protein by hK6 and determined the cleavage sites at the N-terminal end of the protein. Inhibition of hK6 was achieved via binding to different serpins, among which antithrombin III was the most efficient.

Emerging interest in the kallikrein gene family for understanding and diagnosing cancer

Kallikreins are proteolytic enzymes that constitute a subfamily of serine proteases. Novel kallikrein genes were cloned recently, and it was shown that the human kallikrein family contains 15 genes tandemly aligned on chromosomal locus 19q13.3-q13.4. Based on their altered expression in tumor cells, kallikreins may be involved in the pathogenesis and/or progression of cancer. Evidence is presented that certain kallikreins may be exploited as diagnostic cancer biomarkers. Although the function(s) of novel kallikreins is currently unknown, increasing evidence suggests that kallikreins may participate in regulatory enzymatic cascade(s). Elucidation of the function of novel kallikreins largely depends on the availability of active recombinant proteins. Here, the zymogen for kallikrein 13 was overexpressed in Pichia pastoris and biochemically characterized. It was shown that the kallikrein 13 zymogen displays intrinsic catalytic activity leading to autoactivation. A clipped form of kallikrein 13 was identified, indicating autocatalytic cleavage at the internal bond R114-S115. Mature kallikrein 13 displays trypsin-like activity with restricted specificity on synthetic and protein substrates. Combinatorial P1-Lys libraries of tetrapeptide fluorogenic substrates were synthesized and used for the profiling of the P2 specificity of selected kallikreins. Interestingly, it was shown that human kallikrein 13, similarly to PSA, could specifically cleave human plasminogen to generate angiostatin-like fragments, suggesting that specific kallikreins may have antiangiogenic actions. An understanding of the physiology of human kallikreins is emerging with potential clinical applications.

Human kallikrein 13: production and purification of recombinant protein and monoclonal and polyclonal antibodies, and development of a sensitive and specific immunofluorometric assay

BACKGROUND

The aims of this study were to develop immunologic reagents and a sensitive and specific immunoassay for human kallikrein 13 (hK13) and to examine the presence of hK13 in human tissues and biological fluids.

METHODS

Recombinant hK13 protein was produced and purified with use of a Pichia pastoris yeast expression system. The protein was used as an immunogen to generate mouse monoclonal and rabbit polyclonal anti-hK13 antibodies. A sandwich-type immunoassay was developed with these antibodies. The assay was used to measure hK13 in various biological fluids and tissue extracts. Immunohistochemical analysis was also performed on nondiseased and cancerous prostatic sections.

RESULTS

The hK13 immunoassay had a detection limit of 0.05 micro g/L and showed no cross-reactivity with homologous kallikreins. The assay was linear at 0-20 micro g/L, and within-and between-run CVs were <10% (n = 12). hK13 was detected in tissues, including esophagus, tonsil, trachea, lung, cervix, and prostate. hK13 was also found in seminal plasma, amniotic fluid, follicular fluid, ascites of ovarian cancer patients, breast milk, and cytosolic extracts of ovarian cancer tissues. hK13 was immunohistochemically localized in epithelial cells of both nondiseased and cancerous prostate. hK13 appears to be overexpressed in 50% of ovarian cancer tissues compared with healthy ovarian tissues. Recovery of active enzyme added to milk or amniotic fluid was 70-98%, but was <20% when added to serum, suggesting rapid sequestration by protease inhibitors. In fluids and tissue extracts, hK13 was found in its free (approximately 30 kDa) form.

CONCLUSIONS

This immunofluorometric assay for hK13 may be used to examine the value of hK13 as a disease biomarker and to further explore the physiologic and pathobiologic role of this enzyme in human disease.

The structure of human prokallikrein 6 reveals a novel activation mechanism for the kallikrein family

Zyme/protease M/neurosin/human kallikrein 6 (hK6) is a member of the human kallikrein family of trypsin-like serine proteinases and was originally identified as being down-regulated in metastatic breast and ovarian tumors when compared with corresponding primary tumors. Recent evidence suggests that hK6 may serve as a circulating tumor marker in ovarian cancers. In addition, it was described in the brain of Parkinson's disease and Alzheimer's disease patients, where it is implicated in amyloid precursor protein processing. It is thus a biomarker for these diseases. To examine the mechanism of activation of hK6, we have solved the structure of its proform, the first of a human kallikrein family member. The proenzyme displays a fold that exhibits chimeric features between those of trypsinogen and other family members. It lacks the characteristic "kallikrein loop" and forms the six disulfide bridges of trypsin. Pro-hK6 displays a completely closed specificity pocket and a unique conformation of the regions involved in structural rearrangements upon proteolytic cleavage activation. This points to a novel activation mechanism, which could be extrapolated to other human kallikreins.

Expression profiling in squamous carcinoma cells reveals pleiotropic effects of vitamin D3 analog EB1089 signaling on cell proliferation, differentiation, and immune system regulation

The active form of vitamin D3, 1alpha,25-dihydroxyvitamin D3 [1,25-(OH)2D3] is key mediator of calcium homeostasis and is a component of the complex homeostatic system of the skin. 1,25-(OH)2D3 regulates cellular differentiation and proliferation and has broad potential as an anticancer agent. Oligonucleotide microarrays were used to assess profiles of target gene regulation at several points over a 48 h period by the low calcemic 1,25-(OH)2D3 analog EB1089 in human SCC25 head and neck squamous carcinoma cells. One hundred fifty-two targets were identified, composed of 89 up- and 63 down-regulated genes distributed in multiple profiles of regulation. Results are consistent with EB1089 driving SCC25 cells toward a less malignant phenotype, similar to that of basal keratinocytes. Targets identified control inter- and intra-cellular signaling, G protein-coupled receptor function, intracellular redox balance, cell adhesion, and extracellular matrix composition, cell cycle progression, steroid metabolism, and more than 20 genes modulating immune system function. The data indicate that EB1089 performs three key functions of a cancer chemoprevention agent; it is antiproliferative, it induces cellular differentiation, and has potential genoprotective effects. While no evidence was found for gene-specific differences in efficacy of 1,25-(OH)2D3 and EB1089, gene regulation by 1,25-(OH)2D3 was generally more transient. Treatment of cells with 1,25-(OH)2D3 and the cytochrome P450 inhibitor ketoconazole produced profiles of regulation essentially identical to those observed with EB1089 alone, indicating that the more sustained regulation by EB1089 was due to its resistance to inactivation by induced 24-hydroxylase activity. This suggests that differences in action of the two compounds arise more from their relative sensitivities to metabolism than from differing effects on VDR function.

Identification and functional characterization of a human GalNAc [alpha]2,6-sialyltransferase with altered expression in breast cancer

BACKGROUND

We sought to identify genes with altered expression during human breast cancer progression by applying mRNA comparisons of normal and tumor mammary cell lines with increasingly malignant phenotypes. The gene encoding a new sialyltransferase (STM) was found to be down-regulated in tumor cells. Abnormal expression and enzymatic activities of sialyltransferases in tumor cells result in the formation of tumor-associated carbohydrate antigens that can be used for the better understanding of the disease process and are applied for tumor diagnosis and immunotherapy. Altered glycosylation patterns of the MUC1 mucin, in particular, is a target antigen for immunotherapy of breast and other cancers.

MATERIALS AND METHODS

Total RNAs from multiple normal mammary epithelial cell strains and tumor cell lines were compared by differential display and the differential expression of selected cDNAs was confirmed by Northern analyses. Recombinant STM was expressed in COS-7 cells. The substrate and linkage specificity of STM was examined using various oligosaccharides and O-glycosylated proteins as acceptor substrates. The chromosomal localization of the SIATL1 gene was assigned by somatic cell hybrid analysis.

RESULTS

A human sialyltransferase gene was identified by differential display as being down-regulated in breast tumor cell lines as compared to normal mammary epithelial cell strains, and the corresponding full-length cDNA (stm) was cloned. The encoded protein of 374 amino acid residues contained the L- and S-sialylmotifs, two catalytic regions conserved in all functional sialyltransferases. Recombinant STM is an active GalNAc alpha2,6-sialyltransferase with Gal beta 1,3 GalNAc-O-Ser/Thr and (+/- Neu5Ac alpha 2,3) Gal beta 1,3GalNAc-O-Ser/Thr acceptor specificity. The SIATL1 gene, encoding STM, was mapped to the long arm of human chromosome 17 at q23-qter, a region that is nonrandomly deleted in human breast cancers. However, Southern analyses indicated that SIATL1 is usually not grossly rearranged in breast tumors. Northern analyses showed that the gene was widely expressed in normal human tissues, as well as in normal breast and prostate epithelial cell lines, but significantly down-regulated or absent in corresponding tumor cell lines.

CONCLUSIONS

Our findings suggest that aberrant expression of STM sialyltransferase in tumors could be a feature of the malignant phenotype. In breast cancers, the MUC1 mucin is overexpressed and contains shorter O-glycans as compared to the normal mucin. Because STM catalyzes the synthesis of O-glycans, cloning and characterization of its substrate specificity will contribute to the understanding of the molecular mechanisms underlying the aberrant glycosylation patterns of O-glycans and the formation of mucin-related antigens in human breast cancers.

Cystatin M/E Expression is Restricted to Differentiated Epidermal Keratinocytes and Sweat Glands: a New Skin-Specific Proteinase Inhibitor that is a Target for Cross-Linking by Transglutaminase

Using serial analysis of gene expression on cultured human keratinocytes we found high expression levels of genes putatively involved in host protection and defense, such as proteinase inhibitors and antimicrobial proteins. One of these expressed genes was the recently discovered cysteine proteinase inhibitor cystatin M/E that has not been characterized so far at the protein level with respect to tissue distribution and additional biologic properties. Here we report that cystatin M/E has a tissue-specific expression pattern in which high expression levels are restricted to the stratum granulosum of normal human skin, the stratum granulosum/spinosum of psoriatic skin, and the secretory coils of eccrine sweat glands. Low expression levels were found in the nasal cavity. The presence of cystatin M/E in skin and the lack of expression in a variety of other tissues was verified both at the protein level by immunohistochemistry or western blotting, and at the mRNA level by reverse transcriptase polymerase chain reaction or northern blotting. Using biotinylated hexapeptide probes we found that cystatin M/E is an efficient substrate for tissue type transglutaminase and for transglutaminases extracted from stratum corneum, and that it acts as an acyl acceptor but not as an acyl donor. Western blot analysis showed that recombinant cystatin M/E could be cross-linked to a variety of proteins extracted from stratum corneum. In vitro, we found that cystatin M/E expression in cultured keratinocytes is upregulated at the mRNA and protein level, upon induction of differentiation. We demonstrate that cystatin M/E, which has a putative signal peptide, is indeed a secreted protein and is found in vitro in culture supernatant and in vivo in human sweat by enzyme-linked immunosorbent assay or western blotting. Cystatin M/E showed moderate inhibition of cathepsin B but was not active against cathepsin C. We speculate that cystatin M/E is unlikely to be a physiologically relevant inhibitor of intracellular lysosomal cysteine proteinases but rather functions as an inhibitor of self and nonself cysteine proteinases that remain to be identified.

Expression of bcl-2 and bax in cervical intraepithelial neoplasia and invasive squamous cell carcinoma of the uterine cervix

Bcl-2 protein together with the pro-apoptotic protein bax, are thought to function by forming homo- and heterotypic dimers which control the progression to apoptosis. In this immunohistochemical study we investigated the expression of bcl-2 and bax apoptosis related proteins in cervical intraepithelial neoplasia and invasive squamous cell carcinoma of the uterine cervix. Twenty-four cervical intraepithelial neoplasias grade 1-2 (CIN I/II), 38 grade 3 (CIN III), and 53 invasive squamous cell carcinomas (ISCC) were investigated by immunohistochemical staining for bcl-2 and bax protein. Bcl-2 immunoreactivity was found in five of the 24 CIN I/II cases (20.8%), 18 of 38 CIN II cases (47.4%) and nine of 53 ISCC cases (17%). The positivity for CIN III was significantly higher than for CIN I/II or ISCC (p=0.0351 and p=0.0018, respectively). The percentage of bax immunopositivity was somewhat higher in CIN III than in CIN I/II but this slight difference was not statistically significant. Correlation of the immunostaining results with tumor grade revealed a significant difference for bcl-2 which was more frequently immunopositive in well-differentiated tumors than in poorly-differentiated tumors. There was no significant relation between bax expression and tumor differentiation. Our results suggest that alterations of bcl-2 and bax expression may occur as a relatively early event in cervical tumorigenesis.

Cellular distribution of retinoic acid receptor-alpha in benign hyperplastic and malignant human prostates: comparison with androgen, estrogen and progesterone receptor status

OBJECTIVES

Retinoids are unique modulators of gene activity, cell growth and differentiation by binding to a series of nuclear receptors, i.e. all-trans-retinoic acid receptors (RAR) or 9-cis-retinoid receptors (RXR). In this study, the expression of RARalpha was immunohistochemically evaluated in benign, hyperplastic and malignant prostatic tissue and correlated with sex steroid receptor status.

METHODS

Twenty-four cases of BPH and 139 cases of primary prostatic carcinoma were evaluated for RARalpha expression in correlation with androgen (AR), estrogen (ER) and progesterone (PGR) receptor staining, as well as with tumor grade.

RESULTS

RARalpha was detected in the nuclei of epithelial cells in both BPH and prostate carcinoma cases. A modest inverse relationship with grade was present, especially for grade I and grade II tumors. AR staining was intense and a strong inverse relationship with grade was revealed. Although ER and PGR showed nuclear staining in prostatic epithelium, the overall expression for these receptors was low. When RARalpha content was compared to the nuclear AR expression, at least two-fold higher RARalpha levels were observed in AR+ grade II and grade III tumors.

CONCLUSIONS

RARalpha expression can be immunohistochemically evaluated in formalin-fixed paraffin-embedded prostatic tissue. RARalpha expression is significantly elevated in AR+ moderately and poorly differentiated prostate carcinomas. Immunohistochemical determination of RARalpha content may be useful in defining the patient subsets in which retinoid-based treatment may be of clinical value.

Synthetic peptides as putative therapeutic agents in transplantation medicine: application of PEPSCAN to the identification of functional sequences in the extracellular domain of the interleukin-2 receptor beta chain (IL-2Rbeta)

A desired treatment strategy in transplantation medicine is the selective targeting of alloreactive T cells without impairing antileukemic and antiviral activities. One approach is the synthesis of peptides that interfere with the binding of interleukin-2 (IL-2) to its high affinity receptor (IL-2R). This blocks the activation and proliferation of the antigen-activated T cells and the secretion of IL-2. The latter binds to its receptor, via the extracellular domain of the IL-2Rbeta chain, while its cytoplasmic domain is required for intracellular signal transduction. In this study, the PEPSCAN method was applied in order to identify antigenic sequences (epitopes) in the extracellular domain of the IL-2Rbeta. Based on the primary amino acid (aa) sequence of the IL-2Rbeta, a total of 239 overlapping dodecapeptides, spanning the entire sequence of IL-2Rbeta, were synthesized by PEPSCAN and their immunoreactivity was tested by ELISA using monoclonal antibodies (mAbs) specific for IL-2Rbeta such as TU11, Mikbeta1, HuMikbeta1 and TU27. TU11 recognized a linear epitope located in the region 85R-Q(96). None of the 239 synthetic peptides was recognized by TU27. Mikbeta1 (and HuMikbeta1) recognized a discontinuous epitope formed by aa located in the IL-2Rbeta domains L(106) to P(148) and E(170) to A(202). Subsequently, synthetic peptides corresponding to the identified putative epitopic sequences were prepared by solid phase synthesis and their immunogenicity in vivo was assessed by raising polyclonal antibodies. Given that Mikbeta1 and HuMikbeta1 inhibit binding of IL-2 on the IL-2Rbeta, we addressed the question of whether the identified antigenic sequences serve as putative IL-2 binding domains. Synthetic peptides corresponding to these sequences were tested for their ability to compete with IL-2 for binding and, thereby, inhibit IL-2-induced proliferation of mitogen-stimulated human peripheral blood T cells. Sequences 107M-E(118) and 178Y-Q(199) probably represent functional IL-2 binding domains on IL-2Rbeta, since these synthetic peptides significantly inhibited the proliferation of activated T cells and secretion of IL-2.

Immunofluorometric assay of human kallikrein 6 (zyme/protease M/neurosin) and preliminary clinical applications

BACKGROUND

The human kallikrein gene family has contributed the best prostatic biomarkers currently available, including prostate-specific antigen (PSA) and human glandular kallikrein 2 (hK2). Recently, new members of the human kallikrein gene family have been identified. One new member is the KLK6 gene, encoding for human kallikrein 6 (hK6), which is also known as zyme/protease M/neurosin. In this paper, we describe development of antibodies and a sensitive immunofluorometric procedure for hK6 protein.

METHODS

Recombinant hK6 protein was used as immunogen to develop polyclonal antibodies in rabbits and mice. These antibodies were used to develop a sandwich-type time-resolved immunofluorometric procedure for hK6.

RESULTS

The newly developed hK6 immunofluorometric assay has a detection limit of 0.5 microg/L and upper concentration range of 200 microg/L. The assay is highly specific (no detectable cross-reactivity from PSA and hK2) and was used to quantify hK6 protein in various biologic fluids. Highest concentrations of hK6 were found in milk of lactating women, cerebral spinal fluid, nipple aspirate fluid, and breast cyst fluid. hK6 was also detected in male and female serum, in the majority of seminal plasmas and in a small fraction of amniotic fluids and breast tumor cytosols. hK6 was not detectable in urine. Chromatographic studies indicated that hK6 is present in these biologic fluids in its free, 30-kDa form.

CONCLUSIONS

This is the first reported sensitive immunofluorometric procedure for quantifying hK6 protein. hK6 is a secreted proteolytic enzyme that is found at high levels in cerebrospinal fluid and all breast secretions. This assay will facilitate further studies to examine the possible application of hK6 in diagnostics, including cancer and neurodegenerative disorders.

Molecular characterization of zyme/protease M/neurosin (PRSS9), a hormonally regulated kallikrein-like serine protease

The cDNA for the zyme/protease M/neurosin gene (HGMW-approved symbol PRSS9) has recently been identified. Zyme appears to play a role in Alzheimer disease as well as in breast cancer. In this paper, we describe the complete genomic organization of the zyme gene. Zyme spans 10.5 kb of genomic sequence on chromosome 19q13.3-q13.4. The gene consists of seven exons, the first two of which are untranslated. All splice junctions follow the GT/AG rule, and the intron phases are identical to those of many other genes belonging to the same family, i.e., the kallikreins, NES1, and neuropsin. Fine-mapping of the genomic locus indicates that zyme lies upstream of the NES1 gene and downstream from the PSA and KLK2 genes. Tissue expression studies indicate that zyme is expressed mainly in brain tissue, including spinal cord and cerebellum, in mammary gland, and in kidney and uterus. Zyme is regulated by steroid hormones in the breast carcinoma cell line BT-474. Estrogens and progestins, and to a lesser extent androgens, up-regulate the zyme gene in a dose-dependent manner.

EC4 European syllabus for post-graduate training in clinical chemistry. Version 2--1999. European Communities Confederation of Clinical Chemistry, EC4 Register Commission

In modern medicine the undeniable value and indispensability of scientific investigations are now universally recognized both for diagnostic purposes and monitoring of disease and in basic epidemiology. The direct treatment of patients is an undeniable task of doctors in medicine. Progress in laboratory science is largely the result of contributions by scientists with an adequate education and specialisation in the field, i.e. by clinical chemists. Clinical laboratory science has developed on a broad front throughout the European Community, resulting in significant differences in what constitutes a national clinical chemistry service in each state. Clinical chemistry is the medical discipline devoted to obtain, explore and employ chemical knowledge and chemical methods of investigation, in order to procure knowledge about normal and abnormal chemical processes in man. These processes are studied on a general level, in order to get insight into human health and disease, and on a patient-specific level for diagnostic or monitoring purposes. The delimitation of clinical chemistry varies from country to country, since there is no sharp boundary to haematology, immunology, molecular biology and microbiology. One of the main tasks of the clinical chemist is direction and supervision of a laboratory department in a hospital or health service (public or private), where his role involves bridging the gap between rapidly developing laboratory science and technology and the growing knowledge on characteristics of disease. He must possess fundamental biochemical knowledge and have the ability to use this knowledge most appropriately as applied to clinical requirements, i.e. diagnosis of disease and planning and monitoring of therapy. Apart from providing a competent laboratory service, the clinical chemist must be able to function as a consultant to his clinical colleagues and liaise with them in the interpretation of laboratory results. His advice and professional consultation have at least three aspects, i.e. choosing the most appropriate laboratory investigation in a certain case, ensuring that the analyses are performed in the best possible way and correctly reported and, finally, providing information and (most important) interpretation on the significance and consequences of the laboratory data obtained. As the results of laboratory investigations and the consultation of the clinical chemist have a direct and important influence on the treatment of the patient, it is to the benefit of the public that the profession of the clinical chemist is duly regulated.

Re-expression of SPR1 in breast cancer cells by phorbol 12-myristate 13-acetate (PMA) or UV irradiation is mediated by the AP-1 binding site in the SPR1 promoter

BACKGROUND

Invasive tumor cells are characterized by multiple phenotypic changes as a result of the large number of cDNAs being differentially expressed in tumor cells compared to normal progenitors. Expression genetics focuses on changes at the RNA level with the aim of identifying functionally important genes whose aberrant expression in cancer cells is regulated at the level of transcription. These genes were named class II genes and are distinguished from class I genes, which are characterized by genomic mutations, deletions, or other alterations. Reversal of the tumor cell phenotype accompanying normalization of the expression of such genes may be exploited therapeutically if gene expression can be specifically modulated by drugs or other treatments. Considering that genes are coordinately regulated in complex networks, it is likely that the expression of multiple genes can be simultaneously modulated in tumor cells by drugs acting on the signal transduction pathway that regulates their expression. The SPR1 gene is associated with differentiation and its expression is down-regulated or inactivated in malignant cells. Analysis of the SPR1 promoter showed that down-regulation of SPR1 expression in breast tumor cells occurs at the level of transcription. SPR1 presents an example of class II genes, since its expression was up-regulated in tumor cells by phorbol 12-myristate 13-acetate (PMA) or by ultraviolet (UV) irradiation.

MATERIALS AND METHODS

The SPR1 gene was identified by differential display on the basis of its reduced or absent expression in human breast tumor cell lines compared to normal mammary epithelial cell strains. Differential expression was confirmed by Northern blot analysis employing multiple normal and tumor cell lines. The promoter region -619 to +15 of the SPR1 gene was sequenced and analyzed by CAT assays, deletion analysis, and mutagenesis. Up-regulation of SPR1 expression by PMA and UV irradiation was monitored by Northern analysis and analyzed by CAT assays.

RESULTS

The mechanism of down-regulation of SPR1 expression in breast tumor cells was investigated. It was found that the -619 to +15 upstream promoter region is sufficient for SPR1 expression in normal breast cells, but it is transcriptionally silent in most breast tumor cell lines. By deletion analysis and mutagenesis, two upstream cis-acting promoter elements were identified. Our data indicate that the AP-1 element located between -139 and -133 acts as a major enhancer of SPR1 transcription only in normal mammary epithelial cells but not in corresponding tumor cells, whereas the sequences flanking the AP-1 site do not affect its promoter enhancing activity. In addition, a transcriptional repressor was identified that binds unknown factor(s) and is active in both normal and tumor breast cells. Inhibitor function was mapped to a 35-bp element located from -178 to -139 upstream of the human SPR1 mRNA start site. The expression of SPR1 could be induced in the 21MT-2 metastatic breast tumor cell line by PMA treatment or by short UV irradiation via a transcriptional mechanism. AP-1 is the cis element mediating the transcriptional activation of SPR1 by PMA, which induces the expression of AP-1 factors in 21MT-2 cells. Mutation of the AP-1 site abolishes the induction of SPR1 expression by PMA.

CONCLUSIONS

Our results demonstrate that loss of SPR1 expression in breast tumor cells results from impaired transactivation through the AP-1 site in the SPR1 promoter, as well as from the presence of a negative regulatory element active in both normal and tumor cells. Furthermore, our results provide a basis for therapeutic manipulation of down-regulated genes, such as SPR1, in human cancers.

Identification, cloning, and characterization of cystatin M, a novel cysteine proteinase inhibitor, down-regulated in breast cancer

A novel human cystatin gene was identified in a differential display comparison aimed at the isolation of transcriptionally regulated genes involved in invasion and metastasis of breast cancer. Messenger RNAs from primary and metastatic tumor cells isolated from the same patient were compared. A partial cDNA was isolated that was expressed in the primary tumor cell line but not in the metastatic line. The full-length cDNA was cloned and sequenced, and the inferred amino acid sequence was found to encode a novel protein, which we named cystatin M, with 40% homology to human family 2 cystatins and similar overall structure. Cystatin M is expressed by normal mammary cells and a variety of human tissues. The mature cystatin M protein was produced in Escherichia coli as a glutathione S-transferase fusion protein using the pGEX-2T expression system and purified by affinity chromatography. The cystatin M fusion protein displayed inhibitory activity against papain. Native cystatin M protein of approximately 14.5 kDa is secreted and was immunoprecipitated from supernatants of mammary cell cultures using affinity-purified antisera raised against recombinant cystatin M. An N-glycosylated form of cystatin M of 20-22 kDa was co-immunoprecipitated and accounted for about 30-40% of total cystatin M protein. Both forms of native cystatin M also occurred intracellularly. Consistent with the mRNA differential expression, no cystatin M protein was detected in metastatic mammary epithelial tumor cells. Loss of expression of cystatin M is likely associated with the progression of a primary tumor to a metastatic phenotype.

A novel protease homolog differentially expressed in breast and ovarian cancer

BACKGROUND

Using differential display (DD), we discovered a new member of the serine protease family of protein-cleaving enzymes, named protease M. The gene is most closely related by sequence to the kallikreins, to prostate-specific antigen (PSA), and to trypsin. The diagnostic use of PSA in prostate cancer suggested that a related molecule might be a predictor for breast or ovarian cancer. This, in turn, led to studies designed to characterize the protein and to screen for its expression in cancer.

MATERIALS AND METHODS

The isolation of protease M by DD, the cloning and sequencing of the cDNA, and the comparison of the predicted protein structure with related proteins are described, as are methods to produce recombinant proteins and polyclonal antibody preparations. Protease M expression was examined in mammary, prostate, and ovarian cancer, as well as normal, cells and tissues. Stable transfectants expressing the protease M gene were produced in mammary carcinoma cells.

RESULTS

Protease M was localized by fluorescent in situ hybridization analysis to chromosome 19q13.3, in a region to which other kallikreins and PSA also map. The gene is expressed in the primary mammary carcinoma lines tested but not in the corresponding cell lines of metastatic origin. It is strongly expressed in ovarian cancer tissues and cell lines. The enzyme activity could not be established, because of difficulties in producing sufficient recombinant protein, a common problem with proteases. Transfectants were selected that overexpress the mRNA, but the protein levels remained very low.

CONCLUSIONS

Protease M expression (mRNA) may be a useful marker in the detection of primary mammary carcinomas, as well as primary ovarian cancers. Other medical applications are also likely, based on sequence relatedness to trypsin and PSA.

Inhibition of angiogenesis, tumour growth and metastasis by the NO-releasing vasodilators, isosorbide mononitrate and dinitrate

1. The effect of the nitric oxide (NO)-producing nitrovasodilators isosorbide mononitrate (ISMN) and isosorbide dinitrate (ISDN) were assessed on (a) the in vivo model of angiogenesis of the chick chorioallantoic membrane (CAM) and (b) on the growth and metastatic properties of the Lewis Lung carcinoma (LLC) in mice. 2. Isosorbide 5-mononitrate (ISMN) and isosorbide dinitrate (ISDN), inhibited angiogenesis in the CAM dose-dependently. ISMN was more potent in inhibiting this process. Both compounds were capable of completely reversing the angiogenic effect of alpha-thrombin. These effects of ISMN and ISDN on angiogenesis were comparable to those previously observed with sodium nitroprusside which generates NO non-enzymatically. 3. Mice, implanted intramuscularly with LLC, received daily i.p. injections of ISMN for 14 days resulting in a significant decrease in the size of the primary tumour and a reduction in the number and size of metastatic foci in the lungs. ISDN had a similar but less pronounced effect than that observed with ISMN. 4. Addition of ISMN or ISDN to cultures of bovine, rabbit and human endothelial cells and to cultures of LLC cells had no effect on their growth characteristics. 5. These results indicate that ISMN and ISDN inhibit angiogenesis and tumor growth and metastasis in an animal tumour model. The possibility should therefore be considered that these nitrovasodilators which are widely used therapeutically and have well characterized pharmacological profiles, may also possess antitumour properties in the clinic.