Identification and Characterization of KLK-L4, a New Kallikrein-like Gene That Appears to be Down-regulated in Breast Cancer Tissues

Abstract

Kallikreins are a subgroup of serine proteases and these proteolytic enzymes have diverse physiological functions in many tissues. Growing evidence suggests that many kallikreins are implicated in carcinogenesis. In rodents, kallikreins constitute a large multigene family, but in humans, only three genes were identified. By using the positional candidate gene approach, we were able to identify a new kallikrein-like gene, tentatively named KLK-L4 (for kallikrein-like gene 4). This new gene maps to chromosome 19q13.3-q13.4, is formed of five coding exons and four introns, and shows structural similarity to other kallikreins and kallikrein-like genes. KLK-L4 is expressed in a variety of tissues including prostate, salivary gland, breast, and testis. Our preliminary results show that KLK-L4 is down-regulated, at the mRNA level, in breast cancer tissues and breast cancer cell lines. Its expression is regulated by steroid hormones in the breast cancer cell line BT-474. This gene may be involved in the pathogenesis and/or progression of breast cancer and may find applicability as a novel cancer biomarker.Prostate-specific antigen (PSA) 1 testing has revolutionized the management of patients with prostate cancer (1). The PSA gene (KLK3) is a member of the human tissue kallikrein gene family, which is also comprised of human glandular kallikrein 2 (KLK2) (2) and pancreatic/renal kallikrein (KLK1) (3) genes. More recently, new serine proteases with a high degree of homology to the kallikrein genes were cloned (4 -9). The successful diagnostic use of PSA in prostate cancer suggests that other related or unrelated molecules might be discovered and serve as diagnostic tests for breast, ovarian, and other cancers. In addition to PSA, human glandular kallikrein 2 (encoded by the KLK2 gene) may be useful as an adjuvant diagnostic marker for prostate cancer (10). Accumulating evidence indicates that some members of the kallikrein gene family are implicated in carcinogenesis. The normal epithelial cell-specific 1 gene (NES1) was found to be a tumor suppressor (11) that is down-regulated during breast cancer progression. The zyme/ protease M/neurosin gene is expressed in primary breast cancers but is down-regulated at metastatic sites (4).The large size of the kallikrein gene family in other species, such as rat and mouse, where kallikreins are encoded by 13-24 genes (12-13), and the recent identification of new kallikreinlike genes suggested that the human kallikrein gene family may be larger than previously thought. The rodent kallikrein genes are located in clusters on chromosome 7, and the region between two mouse kallikrein genes in a cluster can be as small as 3-7 kb (14).In our efforts to identify new kallikrein-like genes that might be useful as diagnostic and/or prognostic markers for cancer, we studied a genomic area of ϳ300 kb around chromosome 19q13.3-q13.4, where the known human kallikrein genes are localized. We were able to identify three new kallikrein-like genes; KLK-L1 (for kallikrein-like gene 1) (15) KLK-L2 (fo...

TheTMPRSS2 gene encoding transmembrane serine protease is overexpressed in a majority of prostate cancer patients: Detection of mutatedTMPRSS2 form in a case of aggressive disease

“…This result is similar to the recent finding of the higher transcript levels of the KLK15 gene usually seen in prostate cancer patients with late-stage disease and tumors of higher grade. 11 On the other hand, our results from cell line variants of LNCaP indicated downregulation of TMPRSS2 mRNA in androgen-independent LNCaP cells, 5 which is why the results are somewhat contradictory. However, the LNCaP cell line has been derived from a lymph node metastasis of prostate cancer and the changes in expression detected in LNCaP cells are not comparable to the expression in prostate tissue in every case, as shown in our previous study.…”

“…10 KLK-L4 in turn is downregulated in breast cancer. 11 One important task in the future will be to clarify the exact functions of kallikreins and other types of serine proteases during the initiation and progression of cancer.…”

Selenium binding protein 1 in ovarian cancer

“…Hence, our androgen treatment studies illustrated that there is a difference of SELENBP1 expression in response to androgen between HOSE cells and ovarian cancer cells. To investigate whether this is a general androgenic response, we determined the transcript levels of another androgen-regulated gene, human kallikrein 13 (hK13), 20 by the same treatment. Hk13 mRNA levels have similar fold changes as SELENBP1 after DHT treatment in all cell lines, except DOV13, in which hk13 mRNA level increased after DHT treatment (data not shown), suggesting that there is a genuine difference in the androgen pathway between normal HOSE and ovarian cancer cells.…”

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

“…Investigations are proceeding as sensitive and specific assays measuring the gene expression or protein mass of each newly identified member of the kallikrein family become available. Tissue expression of the kallikreins examined to date appears to be down-regulated in aggressive forms of breast cancer (hK3 (PSA) (Levesque et al, 1998), hK10 (Liu et al, 1996;Goyal et al, 1998), hK13 (Yousef et al, 2000) and hK6 (Anisowicz et al, 1996)) and up-regulated in ovarian cancer (hK4 (Obiezu et al, 2002), hK10 (Luo et al, 2001), hK5 (Kim et al, 2001), hK8 (Magklara et al, 2001) and hK6 (Tanimoto et al, 2001)). …”