Low cell motility induced by hsp27 overexpression decreases osteolytic bone metastases of human breast cancer cells in vivo.

The mechanisms controlling the formation of osteolytic bone metastases in patients with breast cancer are still poorly understood. To explore the role of motility in the establishment of osteolytic bone metastases, we have used a model of bone metastasis in which MDA-MB-231 breast cancer cells exhibiting low (hsp27-transfectants) and high (control-transfectant) endogenous cell motility were compared. We found that MDA-MB-231 cells exhibiting low cell motility were less capable of establishing osteolytic lesions. The number and the area of the osteolytic lesions in mice inoculated with low motility cells were both significantly smaller. Histomorphometry of bone lesions also demonstrated less tumor area in mice bearing hsp27 transfectants although there was no difference in the osteoclast number per square millimeter of tumor-bone interface. These data suggest that cell motility may be an important mechanism in the metastatic cascade of breast cancer cells to the bone and that controlling cell motility may be a useful target to prevent the establishment of osteolytic bone metastases.     

A CTGF-RUNX2-RANKL Axis in Breast and Prostate Cancer Cells Promotes Tumor Progression in Bone

Metastasis to bone is a frequent occurrence in patients with breast and prostate cancers and inevitably threatens the patient's quality of life and survival. Identification of cancer-derived mediators of bone metastasis and osteolysis may lead to novel therapeutic strategies. In this study, we established highly bone-metastatic PC3 prostate and MDA-MB-231 (MDA) breast cancer cell sublines by in vivo selection in mice. In bone-metastatic cancer cells, the expression and secretion of connective tissue growth factor (CTGF) were highly upregulated. CTGF knockdown in bone-metastatic cells decreased invasion activity and MMP expression. RUNX2 overexpression in the CTGF knockdown cells restored the invasion activity and MMP expression. In addition, CTGF increased RUNX2 protein stability by inducing its acetylation via p300 acetyl transferase. The integrin αvβ3 receptor mediated these effects of CTGF. Furthermore, CTGF promoted RUNX2 recruitment to the RANKL promoter, resulting in increased RANKL production from the tumor cells and subsequent stimulation of osteoclastogenesis from precursor cells. In addition, animal model with injection of CTGF knocked-down prostate cancer cells into 6-week old BALB/c male mice showed reduced osteolytic lesions. More importantly, the expression levels of CTGF and RANKL showed a strong positive correlation in human primary breast tumor tissues and were higher in bone metastases than in other site metastases. These findings indicate that CTGF plays crucial roles for osteolytic bone metastasis both by enhancing invasiveness of tumor cells and by producing RANKL for osteoclastogenesis. Targeting CTGF may lead to the development of effective preventive and therapeutic strategies for osteolytic metastasis. © 2019 American Society for Bone and Mineral Research.     

The ubiquitin E3 ligase WWP1 decreases CXCL12-mediated MDA231 breast cancer cell migration and bone metastasis

Advanced breast cancers preferentially metastasize to bone where cells in the bone microenvironment produce factors that enhance breast cancer cell homing and growth. Expression of the ubiquitin E3 ligase WWP1 is increased in some breast cancers, but its role in bone metastasis has not been investigated. Here, we studied the effects of WWP1 and itch, its closest family member, on breast cancer bone metastasis. First, we immunostained a multi-tumor tissue microarray and a breast cancer tissue microarray and demonstrated that WWP1 and ITCH are expressed in some of breast cancer cases. We then knocked down WWP1 or itch in MDA-MB-231 breast cancer cells using shRNA and inoculated these cells and control cells into the left ventricle of athymic nude mice. Radiographs showed that mice given shWWP1 cells had more osteolytic lesions than mice given control MDA-MB-231 cells. Histologic analysis confirmed osteolysis and showed significantly increased tumor area in bone marrow of the mice. WWP1 knockdown did not affect cell growth, survival or osteoclastogenic potential, but markedly increased cell migration toward a CXCL12 gradient in vitro. Furthermore, WWP1 knockdown significantly reduced CXCL12-induced CXCR4 lysosomal trafficking and degradation. In contrast, itch knockdown had no effect on MDA-MB-231 cell bone metastasis. Taken together, these findings demonstrate that WWP1 negatively regulates cell migration to CXCL12 by limiting CXCR4 degradation to promote breast cancer metastasis to bone and highlight the potential utility of WWP1 as a prognostic indicator for breast cancer bone metastasis.     

A bone-seeking clone exhibits different biological properties from the MDA-MB-231 parental human breast cancer cells and a brain-seeking clone in vivo and in vitro.

Breast cancer has a predilection for spreading to bone. The mechanism of preferential metastasis of breast cancer to bone is unknown. We hypothesize that breast cancer cells that develop bone metastases have the capacity to facilitate their colonization in bone. To examine this hypothesis, we established bone-seeking (MDA-231BO) and brain-seeking (MDA-231BR) clones of the human breast cancer cell line MDA-MB-231 by repeated sequential passages in nude mice and in vitro of metastatic cells obtained from bone and brain metastases, respectively. These clones were examined for distinguishing biological characteristics and compared with the MDA-231 parental cells (MDA-231P) in vivo and in vitro. Both the MDA-231BR and the MDA-231BO showed identical tumorigenicity to MDA-231P at the orthotopic site. MDA-231P that was inoculated into the heart developed metastases in bone, brain, ovary, and adrenal glands. On the other hand, MDA-231BO exclusively metastasized to bone with larger osteolytic lesions than MDA-231P. MDA-231BR exclusively disseminated to brain and failed to develop bone metastases. In culture, MDA-231BO produced greater amounts of parathyroid hormone-related protein (PTH-rP) than MDA-231BR and MDA-231P in the absence or presence of transforming growth factor beta (TGF-beta). Furthermore, the anchorage-independent growth of MDA- 231BO in soft agar was not inhibited by TGF-beta, whereas TGF-beta profoundly inhibited the growth of MDA-231P and MDA-231BR. Insulin-like growth factor I (IGF-I) markedly promoted the anchorage-independent growth of MDA-231BO, whereas marginal or no stimulation was observed in MDA-231BR or MDA-231P, respectively. Our data suggest that these phenotypic changes allow breast cancer cells to promote osteoclastic bone resorption, survive, and proliferate in bone, which consequently leads to the establishment of bone metastases.     

Involvement of cell-cell and cell-matrix interactions in bone destruction induced by metastatic MDA-MB-231 human breast cancer cells in nude mice

To clarify the mechanisms of bone destruction associated with bone metastases, we studied an animal model in which inoculation of MDA-MB-231 human breast cancer cells into the left cardiac ventricle of female nude mice causes osteolytic lesions in bone using morphological techniques. On the bone surfaces facing the metastatic tumor cells, there existed many tartrate-resistant acid phosphatase (TRAP)-positive multinucleated osteoclasts. TRAP-positive mononuclear osteoclast precursor cells were also observed in the tumor nests. Immunohistochemical studies showed that the cancer cells produced parathyroid hormone-related protein (PTHrP) but not receptor activator of NF-κB ligand (RANKL). Histochemical and immunohistochemical examinations demonstrated that alkaline phosphatase and RANKL-positive stromal cells were frequently adjacent to TRAP-positive osteoclast-like cells. Immunoelectron microscopic observation revealed that osteoclast-like cells were in contact with RANKL-positive stromal cells. MDA-MB-231 cells and osteoclastlike cells in the tumor nests showed CD44-positive reactivity on their plasma membranes. Hyaluronan (HA) and osteopontin (OPN), the ligands for CD44, were occasionally colocalized with CD44. These results suggest that tumorproducing osteoclastogenic factors, including PTHrP, upregulate RANKL expression in bone marrow stromal cells, which in turn stimulates the differentiation and activation of osteoclasts, leading to the progression of bone destruction in the bone metastases of MDA-MB-231 cells. Because the interactions between CD44 and its ligands, HA and OPN, have been shown to upregulate osteoclast differentiation and function, in addition to the cell-cell interactions mediated by RANK and RANKL, the cell-matrix interactions mediated by these molecules may also contribute to the progression of osteoclastic bone destruction.     

Monitoring metastatic behavior of human tumor cells in mice with species-specific polymerase chain reaction: elevated expression of angiogenesis and bone resorption stimulators by breast cancer in bone metastases.

Tumor-stroma interactions are of primary importance in determining the pathogenesis of metastasis. Here, we describe the application of sensitive competitive polymerase chain reaction (PCR) techniques for detection and quantitation of human breast cancer cells (MDA-MB-231) in an in vivo mouse model of experimental metastasis. Human-specific oligonucleotide primers in competitive PCR reactions were used to quantify the amount of MDA-MB-231 cells per tissue per organ. Using this species-specific (semi)quantitative PCR approach, gene expression patterns of (human) tumor cells or (mouse) stromal cells in metastatic lesions in the skeleton or soft tissues were investigated and compared. In all metastatic lesions, MDA-MB-231 cells express angiogenic factors (vascular endothelial growth factors [VEGFs]; VEGF-A, -B, and -C) and bone-acting cytokines (parathyroid hormone-related protein [PTHrP] and macrophage colony-stimulating factor [M-CSF]). In these metastases, PECAM-1-positive blood vessels and stromal cells of mouse origin are detected. The latter express angiogenic factors and markers of sprouting vessels (VEGF receptors flt-1/flk - 1/flk-4 and CD31/PECAM-1). Strikingly, steady-state messenger RNA (mRNA) levels of VEGF-A and -B and the major bone resorption stimulators PTHrP and M-CSF by tumor cells were elevated significantly in bone versus soft tissues (p < or = 0.05, p < or = 0.0001, p < or = 0.001, and p < or = 0.05, respectively), indicating tissue-specific expression of these tumor progression factors. In conclusion, MDA-MB-231 breast cancer cells express a variety of factors in vivo that have been implicated in metastatic bone disease and that correlate with poor survival of patients with breast cancer. We hypothesize that the observed up-regulated expression of angiogenic and bone-resorbing factors by the breast cancer cells in the skeleton underlie the clinically observed osteotropism of breast cancer cells and pathogenesis of osteolytic bone metastases. The application of the species-specific competitive PCR-based assay in vivo can provide new information concerning the involvement of gene families in tumor progression and metastatic disease and greatly facilitates the study of tumor-stroma interactions in cancer invasion and metastasis.     

Parathyroid hormone-related protein (PTHrP)-(1-139) isoform is efficiently secreted in vitro and enhances breast cancer metastasis to bone in vivo

Parathyroid hormone-related peptide (PTHrP) is a mediator of local osteolysis due to breast cancer. Three isoforms of PTHrP, (1-139), (1-141), and (1-173), are products of alternative splicing in humans, but the specific contribution of each of these isoforms to osteolytic metastasis caused by breast cancer has not been evaluated. To determine the role of PTHrP isoforms in breast cancer metastasis to bone, the human breast cancer cell line MDA-MB-231 (MDA-231) was stably transfected with cDNAs for human prepro PTHrP-(1-139), -(1-141), or -(1-173). Stable MDA/PTHrP-(1-139) clones expressed more PTHrP mRNA and secreted more PTHrP protein, compared with MDA/PTHrP-(1-141), -(1-173), or parental MDA-231. Parental MDA-231 cells and clones expressing each isoform had similar growth rates in vitro. In a mouse model of bone metastases, the osteolytic lesion area of radiographs was greatest in mice bearing MDA/PTHrP-(1-139) compared with those bearing MDA/PTHrP-(1-141), -(1-173), or parental MDA-231. Ca(++) and plasma PTHrP concentrations were significantly higher in the MDA/PTHrP-(1-139) compared with the MDA/PTHrP-(1-141), -(1-173), or parental MDA-231 groups. These data demonstrate that the PTHrP-(1-139) isoform was produced to a greater extent than PTHrP-(1-141) or -(1-173), and in vivo enhanced osteolysis with increased plasma PTHrP concentrations and hypercalcemia compared with overexpression of PTHrP-(1-141) or -(1-173).     

Rapid detection of candidate metastatic foci in the orthotopic inoculation model of androgen-sensitive prostate cancer cells introduced with green fluorescent protein

BACKGROUND: An in vivo spontaneous metastatic model using androgen-sensitive prostate cancer cells is needed to the better understanding of prostate cancer progression. Orthotopically inoculated LNCaP cells to SCID mice manifests metastases, but it takes no less than 12 weeks to detect them by conventional methods. METHODS: The green fluorescent protein (GFP) gene was introduced into LNCaP cells by conventional lipofection technique. Biological characteristics of a subline (LNCaP-GFP) that expressed GFP at high level were compared to those of the parental cells. LNCaP-GFP cells were orthotopically inoculated to the SCID mouse, and metastases to distant organs were chronologically examined under fluorescence microscopy. RESULTS: There was no difference in growth rates and androgen-responsiveness in vitro between LNCaP-GFP and LNCaP cells. LNCaP-GFP cells inoculated to SCID mice produced prostate specific antigen. Histopathological examination at 12 weeks after inoculation of LNCaP-GFP revealed that metastases were identified as the inoculation of LNCaP cells. Colonies consisting of a few LNCaP-GFP cells, however, were detected in the lung under fluorescence microscopy as early as 4 weeks after inoculation. CONCLUSIONS: Orthotopic inoculation of LNCaP-GFP to SCID mice may provide a useful tool to investigate the molecular mechanism of progression, in particular the early stage of metastasis, of androgen-sensitive prostate cancer cells.     

Circulating interleukin-8 levels explain breast cancer osteolysis in mice and humans

Skeletal metastases of breast cancer and subsequent osteolysis connote a dramatic change in the prognosis for the patient and significantly increase the morbidity associated with disease. The cytokine interleukin 8 (IL-8/CXCL8) is able to directly stimulate osteoclastogenesis and bone resorption in mouse models of breast cancer bone metastasis. In this study, we determined whether circulating levels of IL-8 were associated with increased bone resorption and breast cancer bone metastasis in patients and investigated IL-8 action in vitro and in vivo in mice. Using breast cancer patient plasma (36 patients), we identified significantly elevated IL-8 levels in bone metastasis patients compared with patients lacking bone metastasis (p < 0.05), as well as a correlation between plasma IL-8 and increased bone resorption (p < 0.05), as measured by NTx levels. In a total of 22 ER + and 15 ER − primary invasive ductal carcinomas, all cases examined stained positive for IL-8 expression. In vitro, human MDA-MB-231 and MDA-MET breast cancer cell lines secrete two distinct IL-8 isoforms, both of which were found to stimulate osteoclastogenesis. However, the more osteolytic MDA-MET-derived full length IL-8(1–77) had significantly higher potency than the non-osteolytic MDA-MB-231-derived IL-8(6–77), via the CXCR1 receptor. MDA-MET breast cancer cells were injected into the tibia of nude mice and 7 days later treated daily with a neutralizing IL-8 monoclonal antibody. All tumor-injected mice receiving no antibody developed large osteolytic bone tumors, whereas 83% of the IL-8 antibody-treated mice had no evidence of tumor at the end of 28 days and had significantly increased survival. The pro-osteoclastogenic activity of IL-8 in vivo was confirmed when transgenic mice expressing human IL-8 were examined and found to have a profound osteopenic phenotype, with elevated bone resorption and inherently low bone mass. Collectively, these data suggest that IL-8 plays an important role in breast cancer osteolysis and that anti-IL-8 therapy may be useful in the treatment of the skeletal related events associated with breast cancer.     

肿瘤干细胞表型CD44和CD24在乳腺癌骨转移模型骨髓中的表达及意义

目的 探讨人乳腺癌细胞转移到人骨的乳腺癌骨转移小鼠模型中骨髓肿瘤干细胞表型CD44和CD24的表达及其意义.方法 50只SCID小鼠随机分成实验组和对照组,其中实验组鼠背部植入人骨后随机均分3亚组:A组(MDA-MB-231干细胞亚群1×105个/只)、B组(同A组细胞1×106个/只)和C组(MDA-MB-231亲代细胞1×106个/只);对照组设为D组(阳性对照,未植入人骨,同C组细胞直接注射)、E组(阴性对照,植入人骨,生理盐水注射).各组8周后取人骨、鼠骨等行常规HE染色及CK、CD44、CD24、CXCR4、OPN免疫组织化学标记.Real-time PCR检测CD44、CXCR4、OPN的mRNA水平.结果 B组骨转移率最高(77.8%,P＜0.05).B组中人骨转移灶CD44、CXCR4、OPN抗原表达高于C、D组骨中的表达(均有P＜0.05);CD24抗原则在A、B组人骨转移灶中低表达与C、D组骨中的高表达无统计学意义(P＞0.05).B组CD44mRNA表达水平是C组的15.2倍、D组的21.1倍;B组CXCR4mRNA表达水平是C组8.4倍、D组28.4倍;B组OPN-mRNA表达水平是C组4.8倍、D组11.6倍;而B组CD24的mRNA表达显著低于C、D组(均为30%).结论 利用MDA-MB-231肿瘤干细胞亚群(CD44+/CD24-)可制备高转移率的"人源性"乳腺癌骨转移模型,其机制可能与CD44高表达有关.骨转移相关基因CXCR4、OPN转录上调可能参与其过程.     

Cellular and molecular basis of preferential metastasis of breast cancer to bone

Bone is one of the most preferential target sites for cancer metastasis. Breast cancer has a predilection for spreading to bone, and bone metastasis is one of the major causes of increased morbidity and eventual mortality in breast cancer patients. None of the currently available therapies is effective for curing bone metastases in these patients. Elucidation of the cellular and molecular mechanism by which breast cancer selectively spreads to bone is essential for the development of mechanism-based effective and specific therapeutic interventions for this deleterious complication in breast cancer. Here, two questions are addressed to study the mechanism of breast cancer metastasis to bone: (1) What makes bone a preferential target site of metastasis? (2) What makes breast cancer able to colonize bone? (3) An animal model in which intracardiac inoculation of breast cancer cells selectively causes osteolytic bone metastases was developed. Experimental results obtained using this unique in-vivo model of bone metastasis are described and discussed. Received for publication on Jan. 22, 1999     

miR-223通过IGF-1R及NFIA调控乳腺癌细胞及破骨细胞功能的研究

目的探索miR-223在乳腺癌骨转移微环境中调控乳腺癌细胞、破骨细胞的功能及其机制。 方法采用micro-CT检测野生型及miR-223基因敲除小鼠股骨骨小梁骨体积分数、骨密度等相关数据,并对股骨组织病理切片染色,观察miR-223缺失对破骨活动影响。利用RANKL诱导RAW 264.7细胞分化为破骨细胞的体外模型,研究miR-223在其中的作用及机制。通过MDA-MB-231细胞实验研究miR-223对乳腺癌细胞增殖、凋亡功能的调控作用及机制。 结果miR-223基因敲除小鼠股骨破骨活动明显活跃;miR-223过表达可以通过NFIA基因抑制RNAKL诱导的破骨细胞分化成熟,还可通过抑制IGF-1R及PI3K/Akt信号通路,抑制乳腺癌细胞增殖并促进其凋亡。 结论miR-223是骨转移微环境中抑制乳腺癌骨转移发生发展的保护性因子,可通过抑制破骨细胞分化成熟、破骨活动、乳腺癌细胞增殖及促进乳腺癌细胞凋亡来调节乳腺癌骨转移微环境。     

乳腺癌裸鼠骨转移模型的建立及评估

目的 建立乳腺癌骨转移动物模型并探讨对该转移模型的最佳评估方法.方法 将带GFP标记的人乳腺癌细胞MDA-MB-231注入裸鼠左心室,建立乳腺癌骨转移模型.6周后使用X线机、活体显像系统和病理学检查对裸鼠骨组织进行评估.结果 6周后病理学检查肿瘤细胞已扩散至裸鼠的脑、骨髓腔、肺等组织,X线影像清晰显示骨质破坏的位置及程度,活体显像系统可以观察到肿瘤细胞在裸鼠体内的分布.结论 X线、活体显像和组织学检查3种方法相结合是分析乳腺癌小鼠骨转移模型的最佳方法之一.     

骨形态发生蛋白7在前列腺癌骨转移中的意义

目的 研究骨形态发生蛋白7(BMP7)与前列腺癌骨转移的关系.方法 采用逆转录-聚合酶链反应(RT-PCR)法检测人前列腺癌PC-3、乳腺癌细胞MDA-MB-231、肾癌细胞KETR-3、膀胱癌细胞T24、胃癌细胞MGC-803中BMP7 mRNA表达.免疫组织化学PV法检测45例有骨转移,42例无骨转移前列腺癌患者前列腺癌组织的BMP7蛋白表达.结果 RT-PCR结果显示,BMP7相对吸光度均值在前列腺癌PC-3细胞(9.59×10-1±1.67×10-2)和乳腺癌细胞(9.50×10-1±3.89×10-2)显著增高;与胃癌细胞MGC-803(2.93×10-1±1.33×10-2)、膀胱癌细胞T24(2.96×10-1±1.21×10-2)、肾癌细胞KETR-3(3.26×10-1±1.53×10-2)比较,差异有统计学意义(P＜0.05).免疫组织化学结果显示,骨转移前列腺癌组BMP7表达吸光度均值(74.80±5.76)明显高于无骨转移前列腺癌组(65.94±1.76),两组差异有统计学意义(P＜0.05).结论 BMP7在嗜骨性转移的前列腺癌细胞中,以及有转移的前列腺癌组织中的高表达,表明BMP7与前列腺癌骨转移有关.     

Breast cancer increases osteoclastogenesis by secreting M-CSF and upregulating RANKL in stromal cells

BACKGROUND: Breast cancer metastasis to bone causes resorption of the mineralized matrix by osteoclasts.Macrophage colony stimulating factor (M-CSF)and receptor activator of the NF-kappaB ligand (RANKL) are produced by stromal cells and are essential for osteoclast formation. The human breast cancer cell line, MDA-MB-231, reliably forms bone metastases in a murine model and stimulates osteoclast formation in culture. We hypothesized that MDA-MB-231 stimulates osteoclast formation through secretion of M-CSF and/or RANKL. MATERIALS AND METHODS: We cocultured MDA-MB-231 and a bone marrow derived cell line, UAMS-33, and evaluated the expression of M-CSF and RANKL mRNA. Osteoclast formation was assessed using these cells added to hematopoietic cell cultures. RESULTS: MDA-MB-231 exhibited constitutive expression of M-CSF mRNA. As expected, addition of recombinant M-CSF (30 ng/ml) and RANKL (30 ng/ml) to hematopoietic osteoclast precursors supported osteoclast formation, while the addition of soluble RANKL alone or MDA-231 without added RANKL did not. Notably, coculture of MDA-231 with hematopoietic cells and added soluble RANKL stimulated significant osteoclast formation, indicating that MDA-231 served as an effective source for M-CSF. MDA-231 did not express RANKL. However, when cocultured with the murine bone marrow stromal cell line UAMS-33, RANKL expression was significantly increased in the latter cells. MDA-231 also stimulated osteoclast formation in coculture with UAMS-33 and hematopoietic cells. CONCLUSIONS: We conclude that MDA-MB-231 increases osteoclast formation by secreting adequate amounts of M-CSF protein and enhancing the expression of RANKL by stromal support cells. The ability to stimulate osteoclasts may explain the ability to metastasize to bone.     

COX-2 induces IL-11 production in human breast cancer cells

BACKGROUND: Cyclooxygenase-2 (COX-2) is overexpressed in 40% of human invasive breast cancers. Interleukin-11 (IL-11), a potent mediator of osteoclastogenesis, is involved in breast cancer metastasis to bone. Since breast cancers that overexpress COX-2 are associated with a higher rate of metastasis to bone, we hypothesized that COX-2 expression in tumor cells would induce IL-11. MATERIALS AND METHODS: We transfected MCF-7 (poorly metastatic) and MDA-231 (highly metastatic) human breast cancer cell lines with COX-2 expression vectors. COX-2 overexpression was confirmed by Western blot and PGE(2) immunoassay, and IL-11 production was measured by immunoassay. We also used a nude mouse model to study COX-2 and IL-11 production from breast cancer cells that metastasized to bone. The bone-seeking clones (BSC) were isolated and cultured from the long bone metastases. RESULTS: COX-2 transfection caused an approximately 5- to 6-fold increase in IL-11 production in both MCF-7 and MDA-231 cells. MDA-435S-COX2-BSC (cells isolated from bone metastasis) produced elevated levels of IL-11 and PGE2 (an important mediator of COX-2) as compared to the parental MDA-435S-COX2 cells. Furthermore, a treatment with low 1- to 2-microm concentration NS-398 or Celecoxib significantly reduced the production of IL-11 in COX-2-transfected MDA-231 cells, thus confirming the involvement of COX-2 in IL-11 induction. CONCLUSION: COX-2-mediated production of IL-11 in breast cancer cells may be vital to the development of osteolytic bone metastases in patients with breast cancer, and a COX-2 inhibitor may be useful in inhibiting this process.     

Prostate cancer metastases alter bone mineral and matrix composition independent of effects on bone architecture in mice — A quantitative study using microCT and Raman spectroscopy

Prostate cancer is the most common primary tumor and the second leading cause of cancer-related deaths in men in the United States. Prostate cancer bone metastases are characterized by abnormal bone remodeling processes and result in a variety of skeletal morbidities. Prevention of skeletal complications is a crucial element in prostate cancer management. This study investigated prostate cancer-induced alterations in the molecular composition and morphological structure of metastasis-bearing bones in a mouse model of prostate cancer using Raman spectroscopy and micro-computed tomography (microCT). LNCaP C4-2B prostate cancer cells were injected into the right tibiae of 5-week old male SCID mice. Upon sacrifice at 8 weeks post tumor inoculation, two out of the ten tumor-bearing tibiae showed only osteoblastic lesions in the radiographs, 4 osteolytic lesions only and 4 mixed with osteoblastic and osteolytic lesions. Carbonate substitution was significantly increased while there was a marked reduction in the level of collagen mineralization, mineral crystallinity, and carbonate:matrix ratio in the cortex of the intact tumor-bearing tibiae compared to contralateral controls. MicroCT analysis revealed a significant reduction in bone volume/total volume, trabecular number and trabecular thickness, as well as significant increase in bone surface/volume ratio in tibiae with osteolytic lesions, suggesting active bone remodeling and bone loss. None of the changes in bone compositional properties were correlated with lesion area from radiographs or the changes in bone architecture from microCT. This study indicates that LNCaP C4-2B prostate cancer metastases alter bone tissue composition independent of changes in architecture, and altered bone quality may be an important contributor to fracture risk in these patients. Raman spectroscopy may provide a new avenue of investigation into interactions between tumor and bone microenvironment.