Procathepsin D in breast cancer: What do we know? Effects of ribozymes and other inhibitors

Abstract

Procathepsin D (pCD) is a major secreted glycoprotein in some human breast and other cancer cell lines. Several groups proposed that pCD served as a growth factor for these cell lines. Secreted pCD has been demonstrated in tissue section, tissue culture supernatants, carcinoma cytosols, and nipple aspirates. Moreover, several clinical studies suggested a potential role for this molecule in metastasis because its concentration in primary tumors correlated with an increased incidence of tumor metastases. In this paper, the effects of pCD were evaluated by proliferation in vitro and by mouse studies in vivo. Subsequent flow cytometry experiments showed the specificity of pCD binding to cancer cells. Cell cultivation showed that addition of either pCD or its activation peptide stimulates growth of cancer cells. These effects can be inhibited both in vitro and in vivo by anti-pCD antibodies. In addition, production of pCD can be inhibited by specifically designed ribozymes. This paper is focused on mitogenic effects of pCD, which seem to involve interaction of the activation peptide with as yet unidentified receptor. Different mechanisms by which pCD could promote development and spread of cancer cells are discussed.

Depletion of procathepsin D gene expression by RNA interference – A potential therapeutic target for breast cancer

“…33 In contrast, our earlier study and a study conducted by Couissi et al, had shown that secreted pCD had a direct effect on the invasive potential of cells. 5,32 Our present result, therefore, is in accordance with these studies where inhibition of pCD secretion significantly affected the invasive potential of cells. Thus, targeted downregulation of pCD by RNAi resulted in changes of MDA-MB-231 cells with reversion to a less invasive phenotype.…”

“…Targeting pCD with antibodies, hammerhead ribozymes and antisense oligonucleotides has been earlier reported. 32,33 Recently, a synthetic siRNA sequence against CD was used in normal cell to determine the role of CD in apoptosis. 34 As individual siRNAs targeted to different regions of a transcript display striking differences in efficacy and specificity, [35][36][37] we designed three siRNA sequences against the entire length of pCD mRNA to obtain maximum silencing.…”

Cathepsin D—Many functions of one aspartic protease

“…In numerous experiments using synthetic AP, anti-AP antibodies or mutant pCD with deleted AP, we demonstrated that AP itself stimulates growth of breast, prostate and lung cancer cells in vitro and in vivo [180,182,183,185,186,190,191,199,200]. Although the mitogenic effect of AP was not confirmed by Glondu et al under their experimental conditions [194], Bazzet et al independently demonstrated mitogenicity of AP in ovarian cancer cells [184].…”

“…Sivaparvathi et al observed that anti-CD antibody inhbited glioblastoma cell invasion through Matrigel [206]. In our experimental conditions, genetic manipulation with the amount of pCD secreted by breast and lung cancer cells strongly influences their ability to cross Matrigel membrane in vitro as well as their metastatic potential in vivo [186,188,189,199]. Invasive capacity in vitro was also stimulated by overexpression of pCD in CD-deficient fibroblasts [27].…”

“…It has been shown that pCD secreted by cancer cells is highly glycosylated and is able to bind to M6P/IGF-II receptor (cation-independent M6PR) on breast cancer cell surface [195][196][197][198]. Numerous studies demonstrated that neither binding nor pCD mitogenic potential is blocked by M6P, anti-M6PR antibodies or pCD deglycosylation [180,190,194,199]. Moreover, we recently showed that mutation in one or both glycosylation sites of pCD only slightly lower pCD mitogenic and pro-invasive activity in vivo and in vitro [200].…”