The antidiabetic drug metformin acts on the bone microenvironment to promote myeloma cell adhesion to preosteoblasts and increase myeloma tumour burden in vivo.

Multiple myeloma is a haematological malignancy that is dependent upon interactions within the bone microenvironment to drive tumour growth and osteolytic bone disease. Metformin is an anti-diabetic drug that has attracted attention due to its direct antitumor effects, including anti-myeloma properties. However, the impact of the bone microenvironment on the response to metformin in myeloma is unknown. We have employed in vitro and in vivo models to dissect out the direct effects of metformin in bone and the subsequent indirect myeloma response. We demonstrate how metformin treatment of preosteoblasts increases myeloma cell attachment. Metformin-treated preosteoblasts increased osteopontin (OPN) expression that upon silencing, reduced subsequent myeloma cell adherence. Proliferation markers were reduced in myeloma cells cocultured with metformin-treated preosteoblasts. In vivo, mice were treated with metformin for 4 weeks prior to inoculation of 5TGM1 myeloma cells. Metformin-pretreated mice had an increase in tumour burden, associated with an increase in osteolytic bone lesions and elevated OPN expression in the bone marrow. Collectively, we show that metformin increases OPN expression in preosteoblasts, increasing myeloma cell adherence. In vivo, this translates to an unexpected indirect pro-tumourigenic effect of metformin, highlighting the importance of the interdependence between myeloma cells and cells of the bone microenvironment.

Matriptase-2 inhibits HECV motility and tubule formation in vitro and tumour angiogenesis in vivo.

The type II transmembrane serine proteases (TTSP) are cell surface proteolytic enzymes that mediate a diverse range of cellular functions, including tumour invasion and metastasis. Matriptase-2 is a member of the TTSP family and has been shown to have a key role in cancer progression. The role of matriptase-2 in angiogenesis and angiogenesis-related cancer progression is currently poorly understood. This study aims to elucidate the role of matriptase-2 in tumour angiogenesis. Matriptase-2 was over-expressed in human vascular endothelial cells, HECV, using a mammalian expression plasmid. The altered cells were used in a number of in vitro and in vivo assays designed to investigate the involvement of matriptase-2 in angiogenesis. Over-expression had no significant effect on the growth and adhesion of HECV cells. However, there was a significant reduction in the motility of the cells and their ability to form tubules in an artificial basement membrane (p < 0.01 for both). HECV(mat2 exp) cells inoculated into CD-1 athymic mice along with either PC-3 prostate cancer cells or MDA-MB-231 breast cancer cells showed a dramatic decrease in tumour development and growth in the prostate tumours (p < 0.01) and a lesser, non-significant, decrease in the breast tumours (p = 0.08). Over-expression of matriptase-2 also decreased urokinase type plasminogen activator total protein levels in HECV and prostate cells. The study concludes that matriptase-2 has the ability to suppress the angiogenic nature of HECV cells in vitro and in vivo. It also suggests that matriptase-2 could have a potential role in prostate and breast tumour suppression through its anti-angiogenic properties.

The influence of matriptase-2 on prostate cancer in vitro: a possible role for ß-catenin.

The type II transmembrane serine proteases (TTSPs) are a family of cell surface proteolytic enzymes contributing to a number of processes, such as tumour invasion and metastasis. Within the TTSPs, matriptase-2 is a relatively newly identified member and this protease has been shown to play a key role in cancer progression. ß-catenin has long been regarded as an oncogene. The deregulation of the ß-catenin signalling pathway plays a significant role in the progression and possibly the development of cancer. However, little is known about the role of matriptase-2 in prostate cancer. This study aimed to examine the correlation between matriptase-2 and ß-catenin. Matriptase-2 was knocked down in the normal prostate cells, PZHPV7 and PNT2C2, using a ribozyme transgene targeting matriptase-2. The altered cells were used in a number of in vitro experiments designed to investigate the involvement of matriptase-2 with ß-catenin and to further characterise its function. The knockdown of matriptase-2 had no effect on cell growth or adhesion but significantly reduced cell motility (PZHPV7 cells, p<0.001; PNT2C2 cells, p=0.001 vs. respective control cells) and invasive capability (PZHPV7 cells, p=0.001; PNT2C2 cells, p=0.007). The knockdown also caused a large increase in ß-catenin protein expression at the cell membrane in PZHPV7 and PNT2C2 cells and a decrease in PC3 cells overexpressing matriptase-2, but did not affect the mRNA levels. Matriptase-2 may have an important impact on prostate cancer progression. The data gained from this study suggest that matriptase-2 protects against the development and progression of prostate cancer by regulating the motility and invasive capabilities of prostate cancer cells. Matriptase-2 also reduces the levels of ß-catenin at the cell membrane. As ß-catenin is highly involved in the regulation of cellular processes, including motility and invasion, the reduction of ß-catenin expression by matriptase-2 may be a possible mechanism by which matriptase-2 functions.

Type II transmembrane serine protease (TTSP) deregulation in cancer.

The Type II transmembrane serine proteases (TTSP) are a relatively newly identified family of proteolytic enzymes that have become the subject of intense scrutiny in the field of cancer research. Advances in genome screening technology have enabled the identification of putative members and the further characterization of existing members. The TTSPs are involved in a diverse range of physiological functions and new roles continue to be discovered. A large majority of these proteases appear to play crucial roles in the development of disease, especially cancer development and progression. This review presents the current knowledge of the biological role of those TTSPs that have been identified in the development and progression of human cancers.

The type II transmembrane serine protease, matriptase-2: Possible links to cancer?

Matriptase-2 is a newly identified member of the Type II Transmembrane Serine Protease (TTSP) family. The expression profile of many members of this family of proteases is frequently altered in cancerous cells and tissues and a number of TTSPs have been linked to cancer progression and development. Matriptase-2 is structurally similar to matriptase-1, a TTSP which has gained recent interest due to its potential to enhance the aggressive nature of cancer cells and its links with a variety of human cancers. Recently, matriptase-2 has been functionally linked to the regulation of iron metabolism; however, there is also evidence to suggest that, as with other members of the TTSPs, matriptase-2 may have a role in cancer development and progression. This article reviews the current literature on matriptase-2, together with its potential roles in physiological and disease states particularly focusing on cancer.

2,2-bis(4-chlorophenyl)-1,1-dichloroethylene stimulates androgen independence in prostate cancer cells through combinatorial activation of mutant androgen receptor and mitogen-activated protein kinase pathways.

Therapy resistance represents a major clinical challenge in disseminated prostate cancer for which only palliative treatment is available. One phenotype of therapy-resistant tumors is the expression of somatic, gain-of-function mutations of the androgen receptor (AR). Such mutant receptors can use noncanonical endogenous ligands (e.g., estrogen) as agonists, thereby promoting recurrent tumor formation. Additionally, selected AR mutants are sensitized to the estrogenic endocrine-disrupting compound (EDC) bisphenol A, present in the environment. Herein, screening of additional EDCs revealed that multiple tumor-derived AR mutants (including T877A, H874Y, L701H, and V715M) are sensitized to activation by the pesticide 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (DDE), thus indicating that this agent may impinge on AR signaling in cancer cells. Further investigation showed that DDE induced mutant AR recruitment to the prostate-specific antigen regulatory region, concomitant with an enhancement of target gene expression, and androgen-independent proliferation. By contrast, neither AR activation nor altered cellular proliferation was observed in cells expressing wild-type AR. Activation of signal transduction pathways was also observed based on rapid phosphorylation of mitogen-activated protein kinase (MAPK) and vasodilator-stimulated phosphoprotein, although only MAPK activation was associated with DDE-induced cellular proliferation. Functional analyses showed that both mutant AR and MAPK pathways contribute to the proliferative action of DDE, as evidenced through selective abrogation of each pathway. Together, these data show that exposure to environmentally relevant doses of EDCs can promote androgen-independent cellular proliferation in tumor cells expressing mutant AR and that DDE uses both mutant AR and MAPK pathways to exert its mitogenic activity.

Unique bisphenol A transcriptome in prostate cancer: novel effects on ERbeta expression that correspond to androgen receptor mutation status.

BACKGROUND: Prostatic adenocarcinomas are dependent on androgen receptor (AR) activity for growth and progression, and therapy for disseminated disease depends on ablation of AR activity. Recurrent tumors ultimately arise wherein AR has been re-activated. One mechanism of AR restoration is via somatic mutation, wherein cells containing mutant receptors become susceptible to activation by alternative ligands, including bisphenol A (BPA). In tumors with specific AR mutations, BPA promotes therapeutic bypass, suggesting significant negative impact to the clinical management of prostate cancer. OBJECTIVE: Our goal was to determine the mechanism of BPA action in cancer cells carrying BPA-responsive AR mutants. METHODS: The molecular signature of BPA activity in prostate cancer cells harboring mutant AR was delineated via genetic microarray analysis. Specificity of BPA action was assessed by comparison with the molecular signature elicited by dihydrotestosterone (DHT). RESULTS: BPA and DHT elicited distinct transcriptional signatures in prostate cancer cells expressing the BPA-responsive mutant AR-T877A. BPA dramatically attenuated estrogen receptor beta (ERbeta) expression; this finding was specific to prostate tumor cells in which BPA induces cellular proliferation. CONCLUSIONS: BPA induces a distinct gene expression signature in prostate cancer cells expressing somatic AR mutation, and a major molecular consequence of BPA action is down-regulation of ERbeta. Since ERbeta functions to antagonize AR function and AR-dependent proliferation, these findings reveal a novel mechanism by which BPA likely regulates cellular proliferation. Future investigation directed at dissecting the importance of ERbeta in the proliferative response to BPA will establish the contribution of this event to adverse effects associated with human exposure.