Diverse biological effect and Smad signaling of bone morphogenetic protein 7 in prostate tumor cells

We found that bone morphogenetic protein (BMP) 7, a member of the BMP family, was strikingly up-regulated during the development of primary prostatic adenocarcinoma in the conditional Pten deletion mouse model. To determine the relevance of this finding to human prostate cancer, we examined the expression of BMPs and BMP receptors (BMPR) as well as the responsiveness to recombinant human BMP7 in a series of human prostate tumor cell lines. All prostatic cell lines tested expressed variable levels of BMP2, BMP4, and BMP7 and at least two of each type I and II BMPRs. In all cases, BMP7 induced Smad phosphorylation in a dose-dependent manner, with Smad5 activation clearly demonstrable. However, the biological responses to BMP7 were cell type specific. BPH-1, a cell line representing benign prostatic epithelial hyperplasia, was growth arrested at G1. In the bone metastasis-derived PC-3 prostate cancer cells, BMP7 induced epithelial-mesenchymal transdifferentiation with classic changes in morphology, motility, invasiveness, and molecular markers. Finally, BMP7 inhibited serum starvation-induced apoptosis in the LNCaP prostate cancer cell line and more remarkably in its bone metastatic variant C4-2B line. Each of the cell lines influenced by BMP7 was also responsive to BMP2 in a corresponding manner. The antiapoptotic activity of BMP7 in the LNCaP and C4-2B cell lines was not associated with a significant alteration in the levels of the proapoptotic protein Bax or the antiapoptotic proteins Bcl-2, Bcl-xl, and X-linked inhibitor of apoptosis. However, in C4-2B cells but not in LNCaP cells, a starvation-induced decrease in the level of survivin was counteracted by BMP7. Taken together, these findings suggest that BMPs are able to modulate the biological behavior of prostate tumor cells in diverse and cell type-specific manner and point to certain mechanisms by which these secreted signaling molecules may contribute to prostate cancer growth and metastasis.     

Loss of expression of bone morphogenetic protein receptor type II in human prostate cancer cells

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta superfamily and signal through a number of membrane receptors. We have previously demonstrated that the loss of expression of BMP receptors (BMPRs) type IA, -IB, and -II (BMP-RIA, -RIB, and -RII) correlates with Gleason score in prostate cancer patients. To evaluate the prognostic value of this observation, we used immunohistochemistry to investigate the expression of BMPRs in association with disease progression in 60 patients. The results demonstrated a significant association between the loss of expression of the three BMPRs and Gleason score and clinical stage. However, only the loss of expression of BMP-RII showed a statistically significant association with 5-year survival rate (P<0.05) and biochemical recurrence-free rate following radical prostatectomy (P<0.005). To elucidate the effect of an abnormal BMP signaling in prostate cancer cells, we transfected dominant-negative BMP-RII (BMP-RIIDN) into the human prostate cancer cell line, PC3M. When a stable clone overexpressing BMP-RIIDN was inoculated subcutaneously into nude mice, the tumor growth rate was approximately 10 times that of control and parental cell line. These observations, taken together, indicate that the loss of BMP-RII expression as measured by immunohistochemistry may be a prognostic marker in prostate cancer patients, and that the loss of BMP-RII function may result in increased tumorigenicity in human prostate cancer cells.     

Bone morphogenetic protein and activin signaling in colorectal cancer

The roles in colon cancer pathogenesis of the transforming growth factor family members bone morphogenetic protein (BMP) and activin have only recently been studied but are increasingly recognized as key. Like their more heavily investigated relative, transforming growth factor β, both BMP and activin are growth-suppressive in normal colonocytes, and their canonical intracellular SMAD signaling is disrupted to abate this suppression. For BMP, there is evidence that non-SMAD signaling pathways may mediate cell proliferation and contribute to the metastatic behavior of colon cancer. BMP signaling in particular is disrupted in the germline of patients with familial juvenile polyposis, an autosomal dominant syndrome with a 12-fold increase in risk for colon cancer over the general population. Researchers are actively investigating cellular and signaling mechanisms by which BMP and activin may initiate and drive proliferation and allow cells to exhibit metastatic properties.     

Repulsive guidance molecules, novel bone morphogenetic protein co-receptors, are key regulators of the growth and aggressiveness of prostate cancer cells

Repulsive guidance molecule (RGM) family members RGMA, RGMB and RGMC are GPI-linked membrane proteins recently identified as co-receptor of bone morphogenetic proteins (BMPs). BMPs are a group of proteins enriched in bone and play important roles in prostate cancer. The current study aimed to investigate roles played by RGMs in prostate cancer. Expression of RGMs was examined in prostate cancer cell lines and prostate cancer tissues using RT-PCR and immunohistochemical staining. Knockdown of each RGM in prostate cancer cells was performed using the respective anti-RGMA, RGMB and RGMC transgenes. A variety of in vitro function tests were employed to analyze the influence on cancer cell functions by RGM knockdown. The implications of RGM knockdown in BMP signalling were also examined using both Western blot and real-time quantitative PCR. Knockdown of RGMA had no effect on cell growth, migration and invasion, but promoted cell-matrix adhesion. Knockdown of RGMB and RGMC increased growth and adhesion, but only RGMB knockdown increased capacities of migration and invasion in PC-3 cells. Further investigations showed an increase in Smad-3 activation and reduced levels of Smad-1 in PC-3 cells by RGMB and RGMC knockdown, and also an up-regulation of ID1, a BMP target gene particularly in exposure to BMP7. RGMs play inhibitory roles in prostate cancer by suppressing cell growth, adhesion, migration and invasion. RGMs can coordinate Smad-dependent signalling of BMPs in prostate cancer cells.     

Cellular interactions in the tropism of prostate cancer to bone

At autopsy >or=80% of prostate cancers have established macrometastases in marrow containing bone. The mechanism(s) to explain this remarkable level of bone involvement remain to be elucidated. We examined the adhesive and invasive behavior of prostate cancer cells to osteoblastic and human bone marrow endothelial cells (HBME-1) in an attempt to explain the tropism of prostate cells for bone. We found an inverse relationship between adhesion and prostate cell tumorigenicity and metastatic potential. Relative cell adhesion of P69 between cell lines was 1.74-fold (95% confidence interval [CI] = 1.15-2.64) and 1.58-fold (95% CI = 0.94-2.68) greater at 1 hr and 2 hr, respectively, than LNCaP that was essentially equivalent to C4-2 cells when using an osteoblastic cell line, D1 as the substrate. Similar results were acquired when HBME-1 were used as substratum. There was a marked increase in adhesion of the poorly tumorigenic cell line P69 as compared to the cancer cells to HBME-1. P69 adhesion was 2.78-fold (95% CI = 1.87-4.84) and 2.0-fold (95% CI = 1.43-2.80) greater at 1 hr and 2 hr, respectively when compared to LNCaP or C4-2 cells. D1 cells, a bone homing osteoblastic precursor, behaved contrary to the metastatic, bone-colonizing C4-2 cell line and bound best to other bone cells but not as well as a non-homing fetal bone marrow-derived cell line, D2. Invasion of prostate cancer cells through HBME-1 lawns was examined at 8 hr and 16 hr. In contrast to the adhesion studies, the invasion of the more aggressive C4-2 cells was 3.46-fold (95% CI = 1.18-10.17) and 2.65-fold (95% CI = 1.26-5.56) greater at 8 hr and 16 hr, respectively than LNCaP cells. Similarly, LNCaP cell invasion was 1.73-fold (95% CI = 0.69-4.37) and 2.35-fold (95% CI = 1.41-3.93) greater at 8 hr and 16 hr, respectively than P69 cells at the invasion of HBME-1 monolayers. At 8 hr, C4-2 cells had 6.0-fold (95% CI = 2.63,13.65) higher invasive potential than P69 cells. Phage display biopanning of LNCaP cells versus C4-2 cells in vitro using 4 separate techniques repeatedly identified the same peptide in support of minimal cell surface changes associated with the ability of C4-2 cells to metastasize to bone. As integrins are vital to cell adhesion and migration, we examined the integrin subunit expression in the prostate cell lines. The expression of integrin subunits is much higher in the nontumorigenic cell line, P69, whereas the differences in integrin expression between LNCaP and C4-2 are negligible. Only alpha(2) and beta(5) integrin subunits increase from LNCaP to C4-2. Given that C4-2 cells spontaneously metastasize to bone in vivo and LNCaP cells do not, these studies imply that the ability of a metastatic prostate cancer cell to colonize the bone is not completely dependent upon the ability of the cancer cell to adhere to either osteoblastic cells or to the bone marrow endothelial cell lining. Therefore, the initial interaction between the bone endothelium or stroma and prostate cells is not accurately referred to as a tropic or homing response. The invasion assay results indicate that the invasive potential of the cell more accurately reflects the bone colonizing potential of a prostate cancer cell. It is likely that bidirectional paracrine interactions, subsequent to marrow adhesion, between prostate cancer cells and the bone microenvironment are what determine the successful colonization of the bone by prostate cancer cells. Further, functional changes in surface proteins that are involved in invasion are likely to occur without major changes in levels of cell surface protein expression. Functional integrin association, substratum usage and outside in signaling are more likely to predict metastatic behavior.     

Genetic variation in bone morphogenetic protein and colon and rectal cancer

Bone morphogenetic proteins (BMP) are part of the TGF-β-signaling pathway; genetic variation in these genes may be involved in colorectal cancer. In this study, we evaluated the association between genetic variation in BMP1 (11 tagSNPs), BMP2 (5 tagSNPs), BMP4 (3 tagSNPs), BMPR1A (9 tagSNPs), BMPR1B (21 tagSNPs), BMPR2 (11 tagSNPs) and GDF10 (7 tagSNPs) with risk of colon and rectal cancer and tumor molecular phenotype. We used data from population-based case-control studies (colon cancer n = 1,574 cases, 1,970 controls; rectal cancer n = 791 cases, 999 controls). We observed that genetic variation in BMPR1A, BMPR1B, BMPR2, BMP2 and BMP4 was associated with risk of developing colon cancer, with 20 to 30% increased risk for most high-risk genotypes. A summary of high-risk genotypes showed over a twofold increase in colon cancer risk at the upper risk category (OR = 2.49 95% CI = 1.95, 3.18). BMPR2, BMPR1B, BMP2 and GDF10 were associated with rectal cancer. BMPR2 rs2228545 was associated with an almost twofold increased risk of rectal cancer. The risk associated with the highest category of the summary score for rectal cancer was 2.97 (95% CI = 1.87, 4.72). Genes in the BMP-signaling pathway were consistently associated with CIMP+ status in combination with both KRAS-mutated and MSI tumors. BMP genes interacted statistically significantly with other genes in the TGF-β-signaling pathway, including TGFβ1, TGFβR1, Smad 3, Smad 4 and Smad 7. Our data support a role for genetic variation in BMP-related genes in the etiology of colon and rectal cancer. One possible mechanism is via the TGF-β-signaling pathway.     

Expression of bone morphogenetic protein receptors type-IA, -IB and -II correlates with tumor grade in human prostate cancer tissues

Bone morphogenetic proteins (BMPs) are potential regulators of prostate cancer cell growth and metastasis that signal through an interaction with BMP membrane receptors (BMPRs) type I and type II. In the present study, Western blot and immunohistochemical analysis of BMPRs were carried out in benign and malignant human prostate tissues to explain the loss of BMP response in human prostate cancer cells. The results demonstrated that the benign prostate specimens expressed high levels of all three BMPRs. In normal prostate, BMPRs were localized predominantly to epithelial cells. Among prostate cancer specimens, well-differentiated cancers were positive for the expression of BMPR-II, BMPR-IA, and BMPR-IB, for the most part. In contrast, only 1 of 10 poorly differentiated prostate cancer cases was positive for each of the three BMPRs (P < 0.005 for all three receptors). Taken together, these results indicate that human prostate cancer cells frequently exhibit loss of expression of BMPRs and suggest that loss of BMPRs may play an important role during the progression of prostate cancer.     

前列腺癌骨转移后骨破坏相关信号通路的研究进展

骨转移是晚期前列腺癌患者常见的并发症之一,骨转移导致的疼痛等骨相关事件(SRE)治疗效果欠佳,预后差,严重影响患者的生命质量。因此,探究前列腺癌骨转移具有重要意义。目前,骨转移的相关机制尚不清楚,宿主微环境和前列腺癌细胞之间相互作用,形成恶性循环是一个重要原因。其中,RANK-RANKL信号通路的研究较为成熟。文章就前列腺癌骨转移相关信号通路的研究现状作一综述,并阐述同一信号分子在不同信号通路中的调控关系。     

透明质酸和骨形态发生蛋白与非小细胞肺癌骨转移的关系

目的探讨透明质酸和骨形态发生蛋白与非小细胞肺癌骨转移的关系。方法选取2012年12月至2014年12月间诊治的非小细胞肺癌骨转移患者47例为非小细胞肺癌骨转移组,同期非小细胞肺癌患者47例为非小细胞肺癌组,同期健康体检人员47例为健康体检组,均行透明质酸和骨形态发生蛋白检测,分析透明质酸和骨形态发生蛋白与非小细胞肺癌骨转移的关系。结果非小细胞肺癌骨转移组患者中,透明质酸、骨形态发生蛋白2、骨形态发生蛋白4、骨形态发生蛋白5、骨形态发生蛋白6均明显高于非小细胞肺癌组和健康体检组,差异均有统计学意义(均P<0.05)。非小细胞肺癌组透明质酸、骨形态发生蛋白2、骨形态发生蛋白4、骨形态发生蛋白5、骨形态发生蛋白6均明显高于健康体检组,差异均有统计学意义(均P<0.05)。透明质酸、骨形态发生蛋白2、骨形态发生蛋白4、骨形态发生蛋白5、骨形态发生蛋白6均与非小细胞肺癌骨转移呈正相关(均P<0.05)。结论透明质酸联合骨形态发生蛋白检测有助于诊断非小细胞肺癌骨转移,具有较高临床价值。     

Hedgehog signaling in prostate cancer

Prostate cancer is the most common malignancy and the second leading cancer-related cause of death in men in the USA. Despite enormous efforts in understanding the molecular basis of prostate cancer, very little progress has been made in prevention and treatment of this often lethal cancer. Recent studies have demonstrated that hedgehog signaling is frequently activated in advanced or metastatic prostate cancers. With small molecule inhibitors available to analyze the hedgehog signaling pathway, a novel rationale for prostate cancer therapy can be devised.     

Human osteocalcin and bone sialoprotein mediating osteomimicry of prostate cancer cells: role of cAMP-dependent protein kinase A signaling pathway

Osteocalcin and bone sialoprotein are the most abundant noncollagenous bone matrix proteins expressed by osteoblasts. Surprisingly, osteocalcin and bone sialoprotein are also expressed by malignant but not normal prostate epithelial cells. The purpose of this study is to investigate how osteocalcin and bone sialoprotein expression is regulated in prostate cancer cells. Our investigation revealed that (a) human osteocalcin and bone sialoprotein promoter activities in an androgen-independent prostate cancer cell line of LNCaP lineage, C4-2B, were markedly enhanced 7- to 12-fold in a concentration-dependent manner by conditioned medium collected from prostate cancer and bone stromal cells. (b) Deletion analysis of human osteocalcin and bone sialoprotein promoter regions identified cyclic AMP (cAMP)-responsive elements (CRE) as the critical determinants for conditioned medium-mediated osteocalcin and bone sialoprotein gene expression in prostate cancer cells. Consistent with these results, the protein kinase A (PKA) pathway activators forskolin and dibutyryl cAMP and the PKA pathway inhibitor H-89, respectively, increased or repressed human osteocalcin and bone sialoprotein promoter activities. (c) Electrophoretic mobility shift assay showed that conditioned medium-mediated stimulation of human osteocalcin and bone sialoprotein promoter activities occurs through increased interaction between CRE and CRE-binding protein. (d) Conditioned medium was found to induce human osteocalcin and bone sialoprotein promoter activities via increased CRE/CRE-binding protein interaction in a cell background-dependent manner, with marked stimulation in selected prostate cancer but not bone stromal cells. Collectively, these results suggest that osteocalcin and bone sialoprotein expression is coordinated and regulated through cAMP-dependent PKA signaling, which may define the molecular basis of the osteomimicry exhibited by prostate cancer cells.