Calcium hydroxyapatite promotes mitogenesis and matrix metalloproteinase expression in human breast cancer cell lines

The prognostic value of ultrasound features and parafibromin expression in parathyroid carcinoma

OBJECTIVES

To investigate prognostic factors related with parathyroid carcinoma (PC) based upon ultrasound (US) parameters and parafibromin expression.

METHODS

Between 2000/01 and 2022/07, thirty-four PC patients with detailed preoperative ultrasonography were enrolled in the research. Immunohistochemical staining of parafibromin was performed on pathological samples of these patients. Based on the expression of parafibromin, the cases were divided into a positive control group (parafibromin expression ≥ 10%) and a negative experimental group (parafibromin expression < 10%). The ultrasound and clinical features of the two groups were analyzed, and Cox regression was used to identify the independent prognostic factors regarding disease-free survival (DFS) and overall survival (OS).

RESULTS

Among 34 patients with parathyroid carcinoma, 26 (76.5%) were parafibromin-positive, while 8 (23.5%) were parafibromin-negative. The mean follow-up time was 72.6 (11.0-179.3) months. During the overall survival period, 7 cases (20.6%) died, and 9 cases (26.5%) experienced recurrence or metastasis. The median overall survival time (interquartile range) was 65.7 (35.5-89.7) months, and the median disease-free survival time (interquartile range) was 38.2 (22.2-69.7) months. The risk of recurrence and metastasis in the parafibromin-negative group was 5.9 times higher than that in parafibromin-positive group (95% CI 1.569-22.190). PC patients with calcification on preoperative ultrasonography had a 9.4 times higher risk of death during the overall survival period compared with patients without calcification (95% CI 1.037-85.915). However, parafibromin expression did not show a significant impact on the prognosis of the overall survival.

CONCLUSIONS

Preoperative US-detected calcification within the lesion is an independent risk factor indicating the shorter OS for PC patients, while loss of parafibromin expression is significant for indicating the recurrence or metastasis of PC patients.

Microcalcifications in breast cancer tissue studied by X-ray absorption, emission, scattering and diffraction

Microcalcifications (MC) are observed in various tissues and in relation to several diseases. For breast cancer, recent studies have reported differences in the nature of the MC and correlations to the degree of malignancy of the neoplasm. Here, investigations of benign, ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC) breast MC using X-ray fluorescence, X-ray absorption spectroscopy and wide-angle X-ray scattering are reported. While Mg has been observed in all MC, only for the benign MC has a rim of crystalline whitlockite been identified as a minor crystalline phase in addition to the major hy-droxy-apatite (HAP) one. MC in DCIS and IDC tissue exhibit a higher abundance of a high-crystallinity HAP phase in comparison with the less well ordered MC in the benign tissue. Moreover, the distribution of other trace elements in the MC, such as Na, S, Cl, Sr and Y, is observed. For the quantitative analysis of the elemental maps, the experimentally determined sample thickness in each pixel has been incorporated as an additional parameter in the fitting process to account for sample roughness.

In-situ collagen mineralization modulates metastatic properties of breast cancer cells

Bone metastasis is the leading cause of morbidity and mortality in advanced-stage breast cancer patients. While most studies focus on the cellular and genetic factors associated with breast cancer metastasis, the role of the extracellular matrix (ECM) of bone in breast cancer metastasis remains elusive. In this study, we recapitulated the bone microenvironment using in-situ mineralized collagen type-I hydrogels and utilized them to understand breast cancer metastasis. Our results indicated successful mineralization of collagen type-I based hydrogels in the presence of serum proteins, which increased as a function of time. There was no difference in the adhesion of breast cancer cells seeded on collagen and mineralized collagen surfaces. However, there was a marked reduction in cell proliferation, down-regulation of various metastatic markers, and decreased migratory phenotype with a concomitant increase in cleaved caspase-3 on mineralized collagen compared to collagen hydrogels. In conclusion, our results suggest an inverse relationship between bone mineralization and the metastatic propensity of breast cancer cells. We further speculate the role of other factors in the skeletal ecosystem for mediating preferential homing of breast cancer cells to the bone microenvironment.

Inhibiting Pathological Calcium Phosphate Mineralization: Implications for Disease Progression

Pathological calcifications, especially calcium phosphate microcalcifications (MCs), appear in most early breast cancer lesions, and their formation correlates with more aggressive tumors and a poorer prognosis. Hydroxyapatite (HA) is a key MC component that crystallizes in the tumor microenvironment. It is often associated with malignant breast cancer lesions and can trigger tumorigenesis in vitro. Here, we investigate the impact of additives on HA crystallization and inhibition, and how precancerous breast cells respond to minerals that are deposited in the presence of these additives. We show that nonstoichiometric HA spontaneously crystallizes in a solution simulating the tumor microenvironmental fluids and exhibits lump-like morphology similar to breast cancer MCs. In this system, the effectiveness of poly(aspartic acid) and poly(acrylic acid) (PAA) to inhibit HA is examined as a potential route to improve cancer prognosis. In the presence of additives, the formation of HA lumps is associated with the promotion or only minimal inhibition of mineralization, whereas the formation of amorphous calcium phosphate (ACP) lumps is followed by inhibition of mineralization. PAA emerges as a robust HA inhibitor by forming spherical ACP particles. When precancerous breast cells are exposed to various HA and ACP minerals, the most influential factors on cell proliferation are the mineral phase and whether the mineral is in the form of discrete particles or particle aggregates. The tumorigenic effects on cells, ranging from cytotoxicity and suppression of proliferation to triggering of proliferation, can be summarized as HA particles < HA aggregates < ACP particles < ACP aggregates. The cellular response to minerals can be attributed to a combination of factors, including mineral phase, crystallinity, morphology, surface texture, aggregation state, and surface potential. These findings have implications for understanding mineral-cell interactions within the tumor microenvironment and suggest that, in some cases, the byproducts of HA inhibition can contribute to disease progression more than HA itself.

The TRPV6 Calcium Channel and Its Relationship with Cancer

Transient receptor potential vanilloid-6 (TRPV6) is a cation channel belonging to the TRP superfamily, specifically the vanilloid subfamily, and is the sixth member of this subfamily. Its presence in the body is primarily limited to the skin, ovaries, kidney, testes, and digestive tract epithelium. The body maintains calcium homeostasis using the TRPV6 channel, which has a greater calcium selectivity than the other TRP channels. Several pieces of evidence suggest that it is upregulated in the advanced stages of thyroid, ovarian, breast, colon, and prostate cancers. The function of TRPV6 in regulating calcium signaling in cancer will be covered in this review, along with its potential applications as a cancer treatment target.

The TRPV6 Calcium Channel and Its Relationship with Cancer

Transient receptor potential vanilloid-6 (TRPV6) is a cation channel belonging to the TRP superfamily, specifically the vanilloid subfamily, and is the sixth member of this subfamily. Its presence in the body is primarily limited to the skin, ovaries, kidney, testes, and digestive tract epithelium. The body maintains calcium homeostasis using the TRPV6 channel, which has a greater calcium selectivity than the other TRP channels. Several pieces of evidence suggest that it is upregulated in the advanced stages of thyroid, ovarian, breast, colon, and prostate cancers. The function of TRPV6 in regulating calcium signaling in cancer will be covered in this review, along with its potential applications as a cancer treatment target.

Tumor therapy by targeting extracellular hydroxyapatite using novel drugs: A paradigm shift

BACKGROUND

It has been shown that tumor microenvironment (TME) hydroxyapatite (HAP) is typically associated with many malignancies and plays a role in tumor progression and growth. Additionally, acidosis in the TME has been reported to play a key role in selecting for a more aggressive tumor phenotype, drug resistance and desensitization to immunotherapy for many types of cancers. TME-HAP is an attractive target for tumor detection and treatment development since HAP is generally absent from normal soft tissue. We provide strong evidence that dissolution of hydroxyapatite (HAP) within the tumor microenvironment (TME-HAP) using a novel therapeutic can be used to kill cancer cells both in vitro and in vivo with minimal adverse effects.

METHODS

We developed an injectable cation exchange nano particulate sulfonated polystyrene solution (NSPS) that we engineered to dissolve TME-HAP, inducing localized acute alkalosis and inhibition of tumor growth and glucose metabolism. This was evaluated in cell culture using 4T1, MDA-MB-231 triple negative breast cancer cells, MCF10 normal breast cells, and H292 lung cancer cells, and in vivo using orthotopic mouse models of cancer that contained detectable microenvironment HAP including breast (MMTV-Neu, 4T1, and MDA-MB-231), prostate (PC3) and colon (HCA7) cancer using 18 F-NaF for HAP and 18 F-FDG for glucose metabolism with PET imaging. On the other hand, H292 lung tumor cells that lacked detectable microenvironment HAP and MCF10a normal breast cells that do not produce HAP served as negative controls. Tumor microenvironment pH levels following injection of NSPS were evaluated via Chemical Exchange Saturation (CEST) MRI and via ex vivo methods.

RESULTS

Within 24 h of adding the small concentration of 1X of NSPS (~7 μM), we observed significant tumor cell death (~ 10%, p < 0.05) in 4T1 and MDA-MB-231 cell cultures that contain HAP but ⟨2% in H292 and MCF10a cells that lack detectable HAP and in controls. Using CEST MRI, we found extracellular pH (pHe) in the 4T1 breast tumors, located in the mammary fat pad, to increase by nearly 10% from baseline before gradually receding back to baseline during the first hour post NSPS administration. in the tumors that contained TME-HAP in mouse models, MMTV-Neu, 4T1, and MDA-MB-231, PC3, and HCA7, there was a significant reduction (p<0.05) in 18 F-Na Fuptake post NSPS treatment as expected; 18 F-  uptake in the tumor = 3.8 ± 0.5 %ID/g (percent of the injected dose per gram) at baseline compared to 1.8 ±0.5 %ID/g following one-time treatment with 100 mg/kg NSPS. Of similar importance, is that 18 F-FDG uptake in the tumors was reduced by more than 75% compared to baseline within 24 h of treatment with one-time NSPS which persisted for at least one week. Additionally, tumor growth was significantly slower (p < 0.05) in the mice treated with one-time NSPS. Toxicity showed no evidence of any adverse effects, a finding attributed to the absence of HAP in normal soft tissue and to our therapeutic NSPS having limited penetration to access HAP within skeletal bone.

CONCLUSION

Dissolution of TME-HAP using our novel NSPS has the potential to provide a new treatment paradigm to enhance the management of cancer patients with poor prognosis.

PI3K/AKT signaling activates HIF1α to modulate the biological effects of invasive breast cancer with microcalcification

Microcalcification (MC) is a valuable diagnostic indicator of breast cancer, and it is reported to be associated with increased tumor aggressiveness and poor prognosis. Nevertheless, the exact potential molecular mechanism is not completely understood. Here, we find that the mineralized invasive breast cancer (IBC) cells not only increased their proliferation and migration, but also showed the characteristic of doxorubicin resistance. The PI3K/AKT signaling pathway is associated with the generation of calcification in IBC, and it activates the transcription and translation of its downstream hypoxia-inducible factor 1α (HIF1α). Knockdown of HIF1α protein significantly downregulated cell proliferation and migration while calcification persists. Meanwhile, calcified breast cancer cells restored sensitivity to doxorubicin because of suppressed HIF1α expression. In addition, we provide initial data on the underlying value of HIF1α as a biomarker of doxorubicin resistance. These findings provide a new direction for exploring microcalcifications in IBC.

Multicellular spheroids containing synthetic mineral particles: an advanced 3D tumor model system to investigate breast precancer malignancy potential according to the mineral type

Mineral particles that form in soft tissues in association with disease conditions are heterogeneous in their composition and physiochemical properties. Hence, it is challenging to study the effect of mineral type on disease progression in a high-throughput and realistic manner. For example, most early breast precancer lesions, termed ductal carcinoma in situ (DCIS), contain microcalcifications (MCs), calcium-containing pathological minerals. The most common type of MCs is calcium phosphate crystals, mainly carbonated apatite; it is associated with either benign or malignant lesions. In vitro studies indicate that the crystal properties of apatite MCs can affect breast cancer progression. A less common type of MCs is calcium oxalate dihydrate (COD), which is almost always found in benign lesions. We developed a 3D tumor model of multicellular spheroids of human precancer cells containing synthetic MC analogs that link the crystal properties of MCs with the progression of breast precancer to invasive cancer. Using this 3D model, we show that apatite crystals induce Her2 overexpression in DCIS cells. This tumor-triggering effect is increased when the carbonate fraction in the MCs decreases. COD crystals, in contrast, decrease Her2 expression in the spheroids, even compared with a control group with no added MC analogs. Furthermore, COD decreases cell proliferation and migration in DCIS monolayers compared to untreated cells and cells incubated with apatite crystals. This finding suggests that COD is not randomly located only in benign lesions-it may actively contribute to suppressing precancer progression in its surroundings. Our model provides an easy-to-manipulate platform to better understand the interactions between mineral particles and their biological microenvironment. A better understanding of the effect of the crystal properties of MCs on precancer progression will potentially provide new directions for better precancer prognosis and treatment.

The added value of apparent diffusion coefficient and microcalcifications to the Kaiser score in the evaluation of BI-RADS 4 lesions

PURPOSE

To explore the added value of combining microcalcifications or apparent diffusion coefficient (ADC) with the Kaiser score (KS) for diagnosing BI-RADS 4 lesions.

METHODS

This retrospective study included 194 consecutive patients with 201 histologically verified BI-RADS 4 lesions. Two radiologists assigned the KS value to each lesion. Adding microcalcifications, ADC, or both these criteria to the KS yielded KS1, KS2, and KS3, respectively. The potential of all four scores to avoid unnecessary biopsies was assessed using the sensitivity and specificity. Diagnostic performance was evaluated by the area under the curve (AUC) and compared between KS and KS1.

RESULTS

The sensitivity of KS, KS1, KS2, and KS3 ranged from 77.1% to 100.0%.KS1 yielded significantly higher sensitivity than other methods (P < 0.05), except for KS3 (P > 0.05), most of all, when assessing NME lesions. For mass lesions, the sensitivity of these four scores was comparable (p > 0.05). The specificity of KS, KS1, KS2, and KS3 ranged from 56.0% to 69.4%, with no statistically significant differences(P > 0.05), except between KS1 and KS2 (p < 0.05).The AUC of KS1 (0.877) was significantly higher than that of KS (0.837; P = 0.0005), particularly for assessing NME (0.847 vs 0.713; P < 0.0001).

CONCLUSION

KS can stratify BI-RADS 4 lesions to avoid unnecessary biopsies. Adding microcalcifications, but not adding ADC, as an adjunct to KS improves diagnostic performance, particularly for NME lesions. ADC provides no additional diagnostic benefit to KS. Thus, only combining microcalcifications with KS is most conducive to clinical practice.

The Role of Calcium in Non-Invasively Imaging Breast Cancer: An Overview of Current and Modern Imaging Techniques

The landscape of breast cancer diagnostics has significantly evolved over the past decade. With these changes, it is possible to provide a comprehensive assessment of both benign and malignant breast calcifications. The biochemistry of breast cancer and calcifications are thoroughly examined to describe the potential to characterize better different calcium salts composed of calcium carbonate, calcium oxalate, or calcium hydroxyapatite and their associated prognostic implications. Conventional mammographic imaging techniques are compared to available ones, including breast tomosynthesis and contrast-enhanced mammography. Additional methods in computed tomography and magnetic resonance imaging are discussed. The concept of using magnetic resonance imaging particularly magnetic susceptibility to characterize the biochemical characteristics of calcifications is described. As we know magnetic resonance imaging is safe and there is no ionization radiation. Experimental findings through magnetic resonance susceptibility imaging techniques are discussed to illustrate the potential for integrating this technique to provide a quantitative assessment of magnetic susceptibility. Under the right magnetic resonance imaging conditions, a distinct phase variability was isolated amongst different types of calcium salts.

Calcinosis universalis and breast cancer: A distinctive association

Calcinosis universalis (CU) is characterised by diffuse deposition of insoluble calcium salt in the skin, subcutaneous tissue or organs. Calcium deposits in the breast may be associated with an increased risk for developing breast cancer. We present a case of a 65-year-old woman diagnosed with CU secondary to undifferentiated connective tissue disease. She developed progressive calcification of her skin, which did not improve with oral medications aimed at reducing the calcification. Investigations to look for possible causes of calcification were all unremarkable. During follow-up, calcification was also found in both her breasts. Initial mammography was reported as fibroadenoma. However, 3 years later, she returned with metastatic breast cancer which presented with a massive pleural effusion of the right lung. Calcinosis universalis should now be considered as a risk factor for breast cancer.

Calcium channel TRPV6 promotes breast cancer metastasis by NFATC2IP

Calcium channel TRPV6 upregulation is associated with poor prognosis of breast cancer by promoting invasion and metastasis, and TRPV6 is a potential target for breast cancer therapy. However, the mechanism by which TRPV6 promotes breast metastasis remains unclear. Here, we report that TRPV6 expression is upregulated in metastatic breast cancers and that TRPV6 overexpression or upregulation accelerates primary breast cancer cell migration. In contrast, TRPV6 suppression decreases cell migration. Mechanistically, TRPV6 activates NFATC2 by increasing NFATC2IP phosphorylation at Ser204, and CDK5 is a candidate kinase that may perform this phosphorylation. Consequently, activated NFATC2 increases breast cancer metastasis by upregulating ADAMTS6 expression. These observations suggest that TRPV6 increases NFATC2 transcriptional activity by increasing NFATC2IP phosphorylation, which consequently upregulates ADAMTS6 expression to promote breast cancer metastasis.

Embracing Mechanobiology in Next Generation Organ-On-A-Chip Models of Bone Metastasis

Bone metastasis in breast cancer is associated with high mortality. Biomechanical cues presented by the extracellular matrix play a vital role in driving cancer metastasis. The lack of in vitro models that recapitulate the mechanical aspects of the in vivo microenvironment hinders the development of novel targeted therapies. Organ-on-a-chip (OOAC) platforms have recently emerged as a new generation of in vitro models that can mimic cell-cell interactions, enable control over fluid flow and allow the introduction of mechanical cues. Biomaterials used within OOAC platforms can determine the physical microenvironment that cells reside in and affect their behavior, adhesion, and localization. Refining the design of OOAC platforms to recreate microenvironmental regulation of metastasis and probe cell-matrix interactions will advance our understanding of breast cancer metastasis and support the development of next-generation metastasis-on-a-chip platforms. In this mini-review, we discuss the role of mechanobiology on the behavior of breast cancer and bone-residing cells, summarize the current capabilities of OOAC platforms for modeling breast cancer metastasis to bone, and highlight design opportunities offered by the incorporation of mechanobiological cues in these platforms.

A time-course Raman spectroscopic analysis of spontaneous in vitro microcalcifications in a breast cancer cell line

Microcalcifications are early markers of breast cancer and can provide valuable prognostic information to support clinical decision-making. Current detection of calcifications in breast tissue is based on X-ray mammography, which involves the use of ionizing radiation with potentially detrimental effects, or MRI scans, which have limited spatial resolution. Additionally, these techniques are not capable of discriminating between microcalcifications from benign and malignant lesions. Several studies show that vibrational spectroscopic techniques are capable of discriminating and classifying breast lesions, with a pathology grade based on the chemical composition of the microcalcifications. However, the occurrence of microcalcifications in the breast and the underlying mineralization process are still not fully understood. Using a previously established model of in vitro mineralization, the MDA-MB-231 human breast cancer cell line was induced using two osteogenic agents, inorganic phosphate (Pi) and β-glycerophosphate (βG), and direct monitoring of the mineralization process was conducted using Raman micro-spectroscopy. MDA-MB-231 cells cultured in a medium supplemented with Pi presented more rapid mineralization (by day 3) than cells exposed to βG (by day 11). A redshift of the phosphate stretching peak for cells supplemented with βG revealed the presence of different precursor phases (octacalcium phosphate) during apatite crystal formation. These results demonstrate that Raman micro-spectroscopy is a powerful tool for nondestructive analysis of mineral species and can provide valuable information for evaluating mineralization dynamics and any associated breast cancer progression, if utilized in pathological samples.

Calcium Signalling in Medulloblastoma: An In Silico Analysis of the Expression of Calcium Regulating Genes in Patient Samples

Dysregulation in calcium signalling is implicated in several cancer-associated processes, including cell proliferation, migration, invasion and therapy resistance. Modulators of specific calcium-regulating proteins have been proposed as promising future therapeutic agents for some cancers. Alterations in calcium signalling have been extensively studied in some cancers; however, this area of research is highly underexplored in medulloblastoma (MB), the most common paediatric malignant brain tumour. Current MB treatment modalities are not completely effective and can result in several long-lasting mental complications. Hence, new treatment strategies are needed. In this study, we sought to probe the landscape of calcium signalling regulators to uncover those most likely to be involved in MB tumours. We investigated the expression of calcium signalling regulator genes in MB patients using publicly available datasets. We stratified the expression level of these genes with MB molecular subgroups, tumour metastasis and patient survival to uncover correlations with clinical features. Of particular interest was CACNA1 genes, in which we were able to show a developmentally-driven change in expression within the cerebellum, MB's tissue of origin, highlighting a potential influence on tumour incidence. This study lays a platform for future investigations into molecular regulators of calcium signalling in MB formation and progression.

3D Printing and Bioprinting to Model Bone Cancer: The Role of Materials and Nanoscale Cues in Directing Cell Behavior

Bone cancer, both primary and metastatic, is characterized by a low survival rate. Currently, available models lack in mimicking the complexity of bone, of cancer, and of their microenvironment, leading to poor predictivity. Three-dimensional technologies can help address this need, by developing predictive models that can recapitulate the conditions for cancer development and progression. Among the existing tools to obtain suitable 3D models of bone cancer, 3D printing and bioprinting appear very promising, as they enable combining cells, biomolecules, and biomaterials into organized and complex structures that can reproduce the main characteristic of bone. The challenge is to recapitulate a bone-like microenvironment for analysis of stromal-cancer cell interactions and biological mechanics leading to tumor progression. In this review, existing approaches to obtain in vitro 3D-printed and -bioprinted bone models are discussed, with a focus on the role of biomaterials selection in determining the behavior of the models and its degree of customization. To obtain a reliable 3D bone model, the evaluation of different polymeric matrices and the inclusion of ceramic fillers is of paramount importance, as they help reproduce the behavior of both normal and cancer cells in the bone microenvironment. Open challenges and future perspectives are discussed to solve existing shortcomings and to pave the way for potential development strategies.

Multiple Pathways for Pathological Calcification in the Human Body

Biomineralization of skeletal components (e.g., bone and teeth) is generally accepted to occur under strict cellular regulation, leading to mineral-organic composites with hierarchical structures and properties optimized for their designated function. Such cellular regulation includes promoting mineralization at desired sites as well as inhibiting mineralization in soft tissues and other undesirable locations. In contrast, pathological mineralization, with potentially harmful health effects, can occur as a result of tissue or metabolic abnormalities, disease, or implantation of certain biomaterials. This progress report defines mineralization pathway components and identifies the commonalities (and differences) between physiological (e.g., bone remodeling) and pathological calcification formation pathways, based, in part, upon the extent of cellular control within the system. These concepts are discussed in representative examples of calcium phosphate-based pathological mineralization in cancer (breast, thyroid, ovarian, and meningioma) and in cardiovascular disease. In-depth mechanistic understanding of pathological mineralization requires utilizing state-of-the-art materials science imaging and characterization techniques, focusing not only on the final deposits, but also on the earlier stages of crystal nucleation, growth, and aggregation. Such mechanistic understanding will further enable the use of pathological calcifications in diagnosis and prognosis, as well as possibly provide insights into preventative treatments for detrimental mineralization in disease.

Printing the Pathway Forward in Bone Metastatic Cancer Research: Applications of 3D Engineered Models and Bioprinted Scaffolds to Recapitulate the Bone-Tumor Niche

Breast cancer commonly metastasizes to bone, resulting in osteolytic lesions and poor patient quality of life. The bone extracellular matrix (ECM) plays a critical role in cancer cell metastasis by means of the physical and biochemical cues it provides to support cellular crosstalk. Current two-dimensional in-vitro models lack the spatial and biochemical complexities of the native ECM and do not fully recapitulate crosstalk that occurs between the tumor and endogenous stromal cells. Engineered models such as bone-on-a-chip, extramedullary bone, and bioreactors are presently used to model cellular crosstalk and bone-tumor cell interactions, but fall short of providing a bone-biomimetic microenvironment. Three-dimensional bioprinting allows for the deposition of biocompatible materials and living cells in complex architectures, as well as provides a means to better replicate biological tissue niches in-vitro. In cancer research specifically, 3D constructs have been instrumental in seminal work modeling cancer cell dissemination to bone and bone-tumor cell crosstalk in the skeleton. Furthermore, the use of biocompatible materials, such as hydroxyapatite, allows for printing of bone-like microenvironments with the ability to be implanted and studied in in-vivo animal models. Moreover, the use of bioprinted models could drive the development of novel cancer therapies and drug delivery vehicles.

OXPHOS-dependent metabolic reprogramming prompts metastatic potential of breast cancer cells under osteogenic differentiation

BACKGROUND

Microcalcification is one of the most reliable clinical features of the malignancy risk of breast cancer, and it is associated with enhanced tumour aggressiveness and poor prognosis. However, its underlying molecular mechanism remains unclear.

METHODS

Clinical data were retrieved to analyse the association between calcification and bone metastasis in patients with breast cancer. Using multiple human breast cancer cell lines, the osteogenic cocktail model was established in vitro to demonstrate calcification-exacerbated metastasis. Migration and invasion characteristics were determined by wound healing and transwell migration. mRNA and protein expression were identified by quantitative PCR and western blotting. Metabolic alterations in breast cancer cells were evaluated using Seahorse Analyser.

RESULTS

The osteogenic differentiation of human breast cancer cells activated the classical TGF-β/Smad signalling pathway and the non-canonical MAPK pathway, which, in turn, exacerbated the progression of epithelial-mesenchymal transition (EMT). The metabolic programme switched to enhancing mitochondrial oxidative phosphorylation (OXPHOS) upon osteogenic differentiation. Rotenone was used to inhibit the OXPHOS complex during osteogenesis to block mitochondrial function, consequently reversing the EMT phenotype.

CONCLUSIONS

This study provides important insights into the mechanisms involved in breast cancer bone metastasis, and outlines a possible strategy to intervene in OXPHOS for the treatment of breast tumours.

Multi-gene signature of microcalcification and risk prediction among Taiwanese breast cancer

Microcalcification is one of the most common radiological and pathological features of breast ductal carcinoma in situ (DCIS), and to a lesser extent, invasive ductal carcinoma. We evaluated messenger RNA (mRNA) transcriptional profiles associated with ectopic mammary mineralization. A total of 109 breast cancers were assayed with oligonucleotide microarrays. The associations of mRNA abundance with microcalcifications and relevant clinical features were evaluated. Microcalcifications were present in 86 (79%) patients by pathological examination, and 81 (94%) were with coexistent DCIS, while only 13 (57%) of 23 patients without microcalcification, the invasive diseases were accompanied with DCIS (χ²-test, P < 0.001). There were 69 genes with differential mRNA abundance between breast cancers with and without microcalcifications, and 11 were associated with high-grade (comedo) type DCIS. Enriched Gene Ontology categories included glycosaminoglycan and aminoglycan metabolic processes and protein ubiquitination, indicating an active secretory process. The intersection (18 genes) of microcalcificaion-associated and DCIS-associated genes provided the best predictive accuracy of 82% with Bayesian compound covariate predictor. Ten genes were further selected for prognostic index score construction, and five-year relapse free survival was 91% for low-risk and 83% for high-risk group (log-rank test, P = 0.10). Our study suggested that microcalcification is not only the earliest detectable radiological sign for mammography screening but the phenomenon itself may reflect the underling events during mammary carcinogenesis. Future studies to evaluate the prognostic significance of microcalcifications are warranted.

Immobilization of Paclitaxel on Hydroxyapatite for Breast Cancer Investigations

A simple method for immobilization of the chemotherapy drug paclitaxel (PTX) on hydroxyapatite nanoparticles (n-HAP) using the biopolymer chitosan as a trapping agent is described focusing on applications involving breast cancer cells. n-HAP with two distinct crystallinity profiles were used: with predominant crystallization along the long axis and with a more homogeneous crystallization in all directions. In the first scenario, the interactions between chitosan and both the OH and PO₄^3- groups on the surface of the nanoparticles are favored and lead to a more efficient attachment of the drug. In this case, PTX is found to remain mostly attached to the n-HAP for at least 24 h, while being dispersed in aqueous solution. During this time, the activity of the drug is inhibited as corroborated by in vitro assays with breast cancer cells. With that, the in vitro experiments revealed distinct effects from the drug-loaded nanoparticles on the cells depending on the experimental conditions. In a short term, that is, in 24 h, the cells exhibit higher viability than those challenged with nonloaded materials. Nevertheless, after 72 h, even a small content of PTX in the presence of n-HAP can reduce the cells' viability via stimulation of the apoptotic phenotype and suppression of survival stimuli.

Dual Energy X-ray Methods for the Characterization, Quantification and Imaging of Calcification Minerals and Masses in Breast

Dual energy (DE) technique has been used by numerous studies in order to detect breast cancer in early stages. Although mammography is the gold standard, the dual energy technique offers the advantage of the suppression of the contrast between adipose and glandular tissues and reveals pathogenesis that is not present in conventional mammography. Both dual energy subtraction and dual energy contrast enhanced techniques were used in order to study the potential of dual energy technique to assist in detection or/and visualization of calcification minerals, masses and lesions obscured by overlapping tissue. This article reviews recent developments in this field, regarding: i) simulation studies carried out for the optimizations of the dual energy technique used in order to characterize and quantify calcification minerals or/and visualize suspected findings, and ii) the subsequent experimental verifications, and finally, the adaptation of the dual energy technique in clinical practice.

TRPV6 as A Target for Cancer Therapy

Two decades ago a class of ion channels, hitherto unsuspected, was discovered. In mammals these Transient Receptor Potential channels (TRPs) have not only expanded in number (to 26 functional channels) but also expanded the view of our interface with the physical and chemical environment. Some are heat and cold sensors while others monitor endogenous and/or exogenous chemical signals. Some TRP channels monitor osmotic potential, and others measure cell movement, stretching, and fluid flow. Many TRP channels are major players in nociception and integration of pain signals. One member of the vanilloid sub-family of channels is TRPV6. This channel is highly selective for divalent cations, particularly calcium, and plays a part in general whole-body calcium homeostasis, capturing calcium in the gut from the diet. TRPV6 can be greatly elevated in a number of cancers deriving from epithelia and considerable study has been made of its role in the cancer phenotype where calcium control is dysfunctional. This review compiles and updates recent published work on TRPV6 as a promising drug target in a number of cancers including those afflicting breast, ovarian, prostate and pancreatic tissues.

Calcium transport and signalling in breast cancer: Functional and prognostic significance

Comprised of a complex network of numerous intertwining pathways, the Ca²⁺ signalling nexus is an essential mediator of many normal cellular activities. Like many other such functions, the normal physiological activity of Ca²⁺ signalling is frequently co-opted and reshaped in cases of breast cancer, creating a potent oncogenic drive within the affected cell population. Such modifications can occur within pathways mediating either Ca²⁺ import (e.g. TRP channels, ORAI-STIM1) or Ca²⁺ export (e.g. PMCA), indicating that both increases and decreases within cellular Ca²⁺ levels have the potential to increase the malignant potential of a cell. Increased understanding of these pathways may offer clinical benefit in terms of both prognosis and treatment; patient survival has been linked to expression levels of certain Ca²⁺ transport proteins, whilst selective targeting of these factors with novel anti-cancer agents has demonstrated a variety of anti-tumour effects in in vitro studies. In addition, the activity of several Ca²⁺ signalling pathways has been shown to influence chemotherapy response, suggesting that a synergistic approach coupling traditional chemotherapy with Ca²⁺ targeting agents may also improve patient outcome. As such, targeted modulation of these pathways represents a novel approach in precision medicine and breast cancer therapy.

Hydroxyapatite mineral enhances malignant potential in a tissue-engineered model of ductal carcinoma in situ (DCIS)

While ductal carcinoma in situ (DCIS) is known as a precursor lesion to most invasive breast carcinomas, the mechanisms underlying this transition remain enigmatic. DCIS is typically diagnosed by the mammographic detection of microcalcifications (MC). MCs consisting of non-stoichiometric hydroxyapatite (HA) mineral are frequently associated with malignant disease, yet it is unclear whether HA can actively promote malignancy. To investigate this outstanding question, we compared phenotypic outcomes of breast cancer cells cultured in control or HA-containing poly(lactide-co-glycolide) (PLG) scaffolds. Exposure to HA mineral in scaffolds increased the expression of pro-tumorigenic interleukin-8 (IL-8) among transformed but not benign cells. Notably, MCF10DCIS.com cells cultured in HA scaffolds adopted morphological changes associated with increased invasiveness and exhibited increased motility that were dependent on IL-8 signaling. Moreover, MCF10DCIS.com xenografts in HA scaffolds displayed evidence of enhanced malignant progression relative to xenografts in control scaffolds. These experimental findings were supported by a pathological analysis of clinical DCIS specimens, which correlated the presence of MCs with increased IL-8 staining and ductal proliferation. Collectively, our work suggests that HA mineral may stimulate malignancy in preinvasive DCIS cells and validate PLG scaffolds as useful tools to study cell-mineral interactions.

Subtype specific targeting of calcium signaling in breast cancer

An important component of breast milk, calcium also appears as radiographically prominent microcalcifications in breast tissue that are often the earliest sign of malignancy. Ionic Ca²⁺ is a universal second messenger that controls a wide swathe of effector pathways integral to gene transcription, cell cycle control, differentiation, proliferation, cell migration, and apoptosis. Whereas prolonged elevation in resting Ca²⁺ levels drives proliferation to initiate and sustain tumor growth, depletion of calcium stores and attenuation of calcium influx pathways underlies tumor chemoresistance and evasion of apoptosis. This paradox of Ca²⁺ homeostasis highlights the challenge of targeting Ca²⁺ signaling pathways for breast cancer therapy. Furthermore, breast cancer is a heterogeneous disease classified into distinct subtypes based on tumor origin, stage of invasiveness and hormone receptor status. Classification is important for tailoring treatment, and in predicting clinical outcome or response to chemotherapy. There have been numerous reports of dysregulated expression, localization or activity of Ca²⁺ channels, regulators and pumps in breast cancer. An important aspect of these alterations is that they are specific to breast cancer subtype, as exemplified by a reciprocal switch in secretory pathway Ca²⁺-ATPase isoforms SPCA1 and SPCA2 depending on receptor status. In this review, we discuss the current knowledge of subtype specific changes in calcium channels and pumps, with a focus on functional insights that may inform new opportunities for breast cancer therapy.

Pathological Mineralization: The Potential of Mineralomics

Pathological mineralization has been reported countless times in the literature and is a well-known phenomenon in the medical field for its connections to a wide range of diseases, including cancer, cardiovascular, and neurodegenerative diseases. The minerals involved in calcification, however, have not been directly studied as extensively as the organic components of each of the pathologies. These have been studied in isolation and, for most of them, physicochemical properties are hitherto not fully known. In a parallel development, materials science methods such as electron microscopy, spectroscopy, thermal analysis, and others have been used in biology mainly for the study of hard tissues and biomaterials and have only recently been incorporated in the study of other biological systems. This review connects a range of soft tissue diseases, including breast cancer, age-related macular degeneration, aortic valve stenosis, kidney stone diseases, and Fahr’s syndrome, all of which have been associated with mineralization processes. Furthermore, it describes how physicochemical material characterization methods have been used to provide new information on such pathologies. Here, we focus on diseases that are associated with calcium-composed minerals to discuss how understanding the properties of these minerals can provide new insights on their origins, considering that different conditions and biological features are required for each type of mineral to be formed. We show that mineralomics, or the study of the properties and roles of minerals, can provide information which will help to improve prevention methods against pathological mineral build-up, which in the cases of most of the diseases mentioned in this review, will ultimately lead to new prevention or treatment methods for the diseases. Importantly, this review aims to highlight that chemical composition alone cannot fully support conclusions drawn on the nature of these minerals.

Mammographic casting-type calcification is an independent prognostic factor in invasive breast cancer

This study aimed to determine whether there is an association between mammographic casting-type calcification and other prognostic factors for invasive breast cancer. We also assessed whether casting-type calcification could be an independent prognostic factor. Invasive breast cancer patient information from January 2010 and January 2013 was retrospectively reviewed. The associations between mammographic casting-type calcification and other clinicopathological factors, including tumor size, node status, grade, progesterone receptor (PR) status, estrogen receptor (ER) status, and human epidermal growth factor receptor 2 (HER2) status, were analyzed. The Kaplan–Meier method and a Cox proportional hazards model were used for survival analyses of disease-free survival (DFS) and overall survival (OS). A total of 1155 invasive breast cancer patients who underwent definitive surgery were included, and 136 cases (11.8%) had casting-type calcification on mammography. In multivariate logistic regression, casting-type calcification was significantly associated with axillary node metastasis, ER-negativity, and HER2 overexpression. Casting-type calcification significantly decreased OS and DFS after a median follow-up of 60 months. This result remained after adjusting other prognostic factors in the multivariate analysis. Casting-type calcification is significantly linked to axillary node metastasis, ER-negativity and HER2 overexpression. Casting-type calcification is therefore an independent prognostic factor for breast cancer patients.

Bone Metastasis: Find Your Niche and Fit in

Metastasis to bones is determined by both intrinsic traits of metastatic tumor cells and properties appertaining to the bone microenvironment. Bone marrow niches are critical for all major steps of metastasis, including the seeding of disseminated tumor cells (DTCs) to bone, the survival of DTCs and microscopic metastases under dormancy, and the eventual outgrowth of overt metastases. In this review, we discuss the role of bone marrow niches in bone colonization. The emphasis is on complicated and dynamic nature of cancer cells-niche interaction, which may underpin the long-standing mystery of metastasis dormancy, and represent a therapeutic target for elimination of minimal residue diseases and prevention of life-taking, overt metastases.

Microcalcifications in breast cancer: From pathophysiology to diagnosis and prognosis

The implementation of mammographic screening programmes in many countries has been linked to a marked increase in early detection and improved prognosis for breast cancer patients. Breast tumours can be detected by assessing several features in mammographic images but one of the most common are the presence of small deposits of calcium known as microcalcifications, which in many cases may be the only detectable sign of a breast tumour. In addition to their efficacy in the detection of breast cancer, the presence of microcalcifications within a breast tumour may also convey useful prognostic information. Breast tumours with associated calcifications display an increased rate of HER2 overexpression as well as decreased survival, increased risk of recurrence, high tumour grade and increased likelihood of spread to the lymph nodes. Clearly, the presence of microcalcifications in a tumour is a clinically significant finding, suggesting that a detailed understanding of their formation may improve our knowledge of the early stages of breast tumourigenesis, yet there are no reports which attempt to bring together recent basic science research findings and current knowledge of the clinical significance of microcalcifications. This review will summarise the most current understanding of the formation of calcifications within breast tissue and explore their associated clinical features and prognostic value.

Secretory pathway Ca2+ -ATPases promote in vitro microcalcifications in breast cancer cells

Calcification of the breast is often an outward manifestation of underlying molecular changes that drive carcinogenesis. Up to 50% of all non-palpable breast tumors and 90% of ductal carcinoma in situ present with radiographically dense mineralization in mammographic scans. However, surprisingly little is known about the molecular pathways that lead to microcalcifications in the breast. Here, we report on a rapid and quantitative in vitro assay to monitor microcalcifications in breast cancer cell lines, including MCF7, MDA-MB-231, and Hs578T. We show that the Secretory Pathway Ca²⁺ -ATPases SPCA1 and SPCA2 are strongly induced under osteogenic conditions that elicit microcalcifications. SPCA gene expression is significantly elevated in breast cancer subtypes that are associated with microcalcifications. Ectopic expression of SPCA genes drives microcalcifications and is dependent on pumping activity. Conversely, knockdown of SPCA expression significantly attenuates formation of microcalcifications. We propose that high levels of SPCA pumps may initiate mineralization in the secretory pathway by elevating luminal Ca²⁺ . Our new findings offer mechanistic insight and functional implications on a widely observed, yet poorly understood radiographic signature of breast cancer.

Non-destructive monitoring of mouse embryo development and its qualitative evaluation at the molecular level using Raman spectroscopy

Current research focuses on embryonic development and quality not only by considering fundamental biology, but also by aiming to improve assisted reproduction technologies, such as in vitro fertilization. In this study, we explored the development of mouse embryo and its quality based on molecular information, obtained nondestructively using Raman spectroscopy. The detailed analysis of Raman spectra measured in situ during embryonic development revealed a temporary increase in protein content after fertilization. Proteins with a β-sheet structure—present in the early stages of embryonic development—are derived from maternal oocytes, while α-helical proteins are additionally generated by switching on a gene after fertilization. The transition from maternal to embryonic control during development can be non-destructively profiled, thus facilitating the in situ assessment of structural changes and component variation in proteins generated by metabolic activity. Furthermore, it was indicated that embryos with low-grade morphology had high concentrations of lipids and hydroxyapatite. This technique could be used for embryo quality testing in the future.

Insights into Biochemical Alteration in Cancer-Associated Fibroblasts by using Novel Correlative Spectroscopy

The microenvironment of a tumor changes chemically and morphologically during cancer progression. Cancer‐stimulated fibroblasts promote tumor growth, however, the mechanism of the transition to a cancer‐stimulated fibroblast remains elusive. Here, the multi‐modal spectroscopic methods Fourier transform infrared imaging (FTIRI), X‐ray absorption spectroscopy (XAS) and X‐ray fluorescence imaging (XFI) are used to characterize molecular and atomic alterations that occur in cancer‐stimulated fibroblasts. In addition to chemical changes in lipids (olefinic and acyl chain) and protein aggregation observed with FTIRI, a new infrared biomarker for oxidative stress in stimulated fibroblasts is reported. Oxidative stress is observed to cause lipid peroxidation, which leads to the appearance of a new band at 1721 cm⁻¹, assigned to 4‐hydroxynonenal. Complementary to FTIRI, XFI is well suited to determining atom concentrations and XAS can reveal the speciation of individual elements. XFI reveals increased concentrations of P, S, K, Ca within stimulated fibroblasts. Furthermore, XAS studies reveal alterations in the speciation of S and Ca in stimulated fibroblasts, which might provide insight into the mechanisms of cancer progression. Using XFI, not only is the concentration change of individual elements observed, but also the subcellular localization. This study demonstrates the wealth of biochemical information provided by a multi‐modal imaging approach and highlights new avenues for future research into the microenvironment of breast tumors.

A 3D printed nano bone matrix for characterization of breast cancer cell and osteoblast interactions

Bone metastasis is one of the most prevalent complications of late-stage breast cancer, in which the native bone matrix components, including osteoblasts, are intimately involved in tumor progression. The development of a successful in vitro model would greatly facilitate understanding the underlying mechanism of breast cancer bone invasion as well as provide a tool for effective discovery of novel therapeutic strategies. In the current study, we fabricated a series of in vitro bone matrices composed of a polyethylene glycol hydrogel and nanocrystalline hydroxyapatite of varying concentrations to mimic the native bone microenvironment for the investigation of breast cancer bone metastasis. A stereolithography-based three-dimensional (3D) printer was used to fabricate the bone matrices with precisely controlled architecture. The interaction between breast cancer cells and osteoblasts was investigated in the optimized bone matrix. Using a Transwell^® system to separate the two cell lines, breast cancer cells inhibited osteoblast proliferation, while osteoblasts stimulated breast cancer cell growth, whereas, both cell lines increased IL-8 secretion. Breast cancer cells co-cultured with osteoblasts within the 3D bone matrix formed multi-cellular spheroids in comparison to two-dimensional monolayers. These findings validate the use of our 3D printed bone matrices as an in vitro metastasis model, and highlights their potential for investigating breast cancer bone metastasis.

A Molecular View of Pathological Microcalcification in Breast Cancer

Breast microcalcification is a potential diagnostic indicator for non-palpable breast cancers. Microcalcification type I (calcium oxalate) is restricted to benign tissue, whereas type II (calcium hydroxyapatite) occurs both in benign as well as in malignant lesions. Microcalcification is a pathological complication of the mammary gland. Over the past few decades, much attention has been paid to exploit this property, which forms the basis for advances in diagnostic procedures and imaging techniques. The mechanism of its formation is still poorly understood. Hence, in this paper, we have attempted to address the molecular mechanism of microcalcification in breast cancer. The central theme of this communication is "how a subpopulation of heterogeneous breast tumor cells attains an osteoblast-like phenotype, and what activities drive the process of pathophysiological microcalcification, especially at the invasive or infiltrating front of breast tumors". The role of bone morphogenetic proteins (BMPs) and tumor associated macrophages (TAMs) along with epithelial to mesenchymal transition (EMT) in manipulating this pathological process has been highlighted. Therefore, this review offers a novel insight into the mechanism underlying the development of microcalcification in breast carcinomas.

3D printed nanocomposite matrix for the study of breast cancer bone metastasis

Bone is one of the most common metastatic sites of breast cancer, but the underlying mechanisms remain unclear, in part due to an absence of advanced platforms for cancer culture and study that mimic the bone microenvironment. In the present study, we integrated a novel stereolithography-based 3D printer and a unique 3D printed nano-ink consisting of hydroxyapatite nanoparticles suspended in hydrogel to create a biomimetic bone-specific environment for evaluating breast cancer bone invasion. Breast cancer cells cultured in a geometrically optimized matrix exhibited spheroid morphology and migratory characteristics. Co-culture of tumor cells with bone marrow mesenchymal stem cells increased the formation of spheroid clusters. The 3D matrix also allowed for higher drug resistance of breast cancer cells than 2D culture. These results validate that our 3D bone matrix can mimic tumor bone microenvironments, suggesting that it can serve as a tool for studying metastasis and assessing drug sensitivity. From the Clinical Editor: Cancer remains a major cause of mortality for patients in the clinical setting. For breast cancer, bone is one of the most common metastatic sites. In this intriguing article, the authors developed a bone-like environment using 3D printing technology to investigate the underlying biology of bone metastasis. Their results would also allow a new model for other researchers who work on cancer to use.

CA1 contributes to microcalcification and tumourigenesis in breast cancer

Background

Although mammary microcalcification is frequently observed and has been associated with poor survival in patients with breast cancer, the genesis of calcification remains unclear. Carbonic anhydrase I (CA1) has been shown to promote calcification by catalysing the hydration of CO₂. This study aimed to determine whether CA1 was correlated with microcalcification and with other processes that are involved in breast cancer tumourigenesis.

Methods

CA1 expression in breast cancer tissues and blood samples was detected using western blotting, real-time PCR, immunohistochemistry and ELISA. Calcification was induced in the cultured 4T1 cell line originating from mouse breast tumours, using ascorbic acid and β-glycerophosphate. Acetazolamide, a chemical inhibitor of CA1, was also added to the culture to determine the role of CA1 in calcification. The MCF-7 human breast cancer cell line was treated with anti-CA1 siRNA and was assessed using a CCK-8 cell proliferation assay, an annexin V cell apoptosis assay, transwell migration assay and a human breast cancer PCR array. The tag SNP rs725605, which is located in the CA1 locus, was genotyped using TaqMan® genotyping.

Results

Increased CA1 expression was detected in samples of breast carcinoma tissues and blood obtained from patients with breast cancer. A total of 15.3 % of these blood samples exhibited a 2.1-fold or higher level of CA1 expression, compared to the average level of CA1 expression in samples from healthy controls. Following the induction of calcification of 4T1 cells, both the number of calcium-rich deposits and the expression of CA1 increased, whereas the calcification and CA1 expression were significantly supressed in the presence of acetazolamide. Increased migration and apoptosis were observed in MCF-7 cells that were treated with anti-CA1 siRNA. The PCR array detected up-regulation of the androgen receptor (AR) and down-regulation of X-box binding protein 1 (XBP1) in the treated MCF-7 cells. Significant differences in the allele and genotype frequencies of rs725605 were detected in the cohort of patients with breast cancer but not in other tumours.

Conclusion

The results of this study suggested that CA1 is a potential oncogene and that it contributes to abnormal cell calcification, apoptosis and migration in breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1707-x) contains supplementary material, which is available to authorized users.

The use of collagen-based scaffolds to simulate prostate cancer bone metastases with potential for evaluating delivery of nanoparticulate gene therapeutics

Prostate cancer bone metastases are a leading cause of cancer-related death in men with current treatments offering only marginally improved rates of survival. Advances in the understanding of the genetic basis of prostate cancer provide the opportunity to develop gene-based medicines capable of treating metastatic disease. The aim of this work was to establish a 3D cell culture model of prostate cancer bone metastasis using collagen-based scaffolds, to characterise this model, and to assess the potential of the model to evaluate delivery of gene therapeutics designed to target bone metastases. Two prostate cancer cell lines (PC3 and LNCaP) were cultured in 2D standard culture and compared to 3D cell growth on three different collagen-based scaffolds (collagen and composites of collagen containing either glycosaminoglycan or nanohydroxyapatite). The 3D model was characterised for cell proliferation, viability and for matrix metalloproteinase (MMP) enzyme and Prostate Specific Antigen (PSA) secretion. Chemosensitivity to docetaxel treatment was assessed in 2D in comparison to 3D. Nanoparticles (NPs) containing siRNA formulated using a modified cyclodextrin were delivered to the cells on the scaffolds and gene silencing was quantified. Both prostate cancer cell lines actively infiltrated and proliferated on the scaffolds. Cell culture in 3D resulted in reduced levels of MMP1 and MMP9 secretion in PC3 cells. In contrast, LNCaP cells grown in 3D secreted elevated levels of PSA, particularly on the scaffold composed of collagen and glycosaminoglycans. Both cell lines grown in 3D displayed increased resistance to docetaxel treatment. The cyclodextrin.siRNA nanoparticles achieved cellular uptake and knocked down the endogenous GAPDH gene in the 3D model. In conclusion, development of a novel 3D cell culture model of prostate cancer bone metastasis has been initiated resulting, for the first time, in the successful delivery of gene therapeutics in a 3D in vitro model. Further enhancement of this model will help elucidate the pathogenesis of prostate cancer and also accelerate the design of effective therapies which can penetrate into the bone microenvironment for prostate cancer therapy.

Vascular Calcification and Stone Disease: A New Look towards the Mechanism

Calcium phosphate (CaP) crystals are formed in pathological calcification as well as during stone formation. Although there are several theories as to how these crystals can develop through the combined interactions of biochemical and biophysical factors, the exact mechanism of such mineralization is largely unknown. Based on the published scientific literature, we found that common factors can link the initial stages of stone formation and calcification in anatomically distal tissues and organs. For example, changes to the spatiotemporal conditions of the fluid flow in tubular structures may provide initial condition(s) for CaP crystal generation needed for stone formation. Additionally, recent evidence has provided a meaningful association between the active participation of proteins and transcription factors found in the bone forming (ossification) mechanism that are also involved in the early stages of kidney stone formation and arterial calcification. Our review will focus on three topics of discussion (physiological influences-calcium and phosphate concentration-and similarities to ossification, or bone formation) that may elucidate some commonality in the mechanisms of stone formation and calcification, and pave the way towards opening new avenues for further research.

Raman spectroscopic sensing of carbonate intercalation in breast microcalcifications at stereotactic biopsy

Microcalcifications are an early mammographic sign of breast cancer and frequent target for stereotactic biopsy. Despite their indisputable value, microcalcifications, particularly of the type II variety that are comprised of calcium hydroxyapatite deposits, remain one of the least understood disease markers. Here we employed Raman spectroscopy to elucidate the relationship between pathogenicity of breast lesions in fresh biopsy cores and composition of type II microcalcifications. Using a chemometric model of chemical-morphological constituents, acquired Raman spectra were translated to characterize chemical makeup of the lesions. We find that increase in carbonate intercalation in the hydroxyapatite lattice can be reliably employed to differentiate benign from malignant lesions, with algorithms based only on carbonate and cytoplasmic protein content exhibiting excellent negative predictive value (93–98%). Our findings highlight the importance of calcium carbonate, an underrated constituent of microcalcifications, as a spectroscopic marker in breast pathology evaluation and pave the way for improved biopsy guidance.

Potential proinflammatory and osteogenic effects of dicalcium silicate particles in vitro

BACKGROUND

Due to their biocompatibility and bioactivity, dicalcium silicate (C2S) and hydroxyapatite (HA) are used as coating materials for prosthetic orthopedic and dental implants or as bone substitute materials to fill bone defects. However, prostheses and bone substitutes can release particles that trigger an immune response in the recipient. The immunological effects of C2S particles have not yet been studied.

OBJECTIVE

The aim of this study was to determine the cytotoxic effects of C2S particles on primary human monocytes, a human monocyte cell line (THP-1) and an osteoblast-like cell line (MG-63). The proinflammatory effects of C2S particles on THP-1 were also detected. Moreover, the osteogenic effects of C2S and HA on MG-63 cells were investigated.

METHODS

Characterization of C2S and HA was performed using scanning electron microscopy (SEM), energy dispersive analysis (EDS), X-ray diffraction (XRD), Brunner-Emmett-Teller (BET) measurements and laser diffraction. The cytotoxic effect of C2S on primary human monocytes as well as THP-1 and MG-63 cells was measured using Trypan blue assays, Cell Counting Kit-8 (CCK-8) assays and flow cytometry to detect apoptosis. THP-1 human monocytes with or without lipopolysaccharide (LPS) stimulation were exposed to C2S and HA for 6 and 24h. Thereafter, the mRNA expression and protein concentrations of MMP-2, MMP-9, TIMP-2, TIMP-1 and TNF-α were evaluated using real-time PCR and ELISA, respectively. RANKL and OPG mRNA expression levels in MG-63 cells were examined using real-time PCR.

RESULTS

No significant cytotoxicity was recorded when cells were directly cultured with C2S/HA particles. After THP-1 cells were cultured with C2S/HA for 24h, MMP-2, MMP-9 and TNF-α expression increased, whereas TIMP-2 and TIMP-1 expression decreased. Compared with HA, C2S slightly increased MMP-9 expression and slightly decreased TIMP-1 expression. The MMP: TIMP ratio increased in the C2S and HA groups; however, HA significantly increased the MMP-9: TIMP-1 ratio compared with C2S. Compared with HA, C2S caused less TNF-α production. C2S/HA did not modify the expression of proinflammatory mediators in LPS-stimulated cells. Furthermore, C2S/HA significantly increased OPG expression and slightly increased RANKL expression in MG-63 cells. C2S and HA decreased the RANKL: OPG ratio.

CONCLUSION

Our in vitro data suggest that C2S is relatively safe when directly cultured with cells. In addition, C2S may exert proinflammatory effects; however, compared with HA, C2S had fewer proinflammatory effects on THP-1. C2S and HA did not alter the LPS-induced production of proinflammatory mediators and had similar osteogenic effects on MG-63 cells.

Detection of breast cancer microcalcification using (99m)Tc-MDP SPECT or Osteosense 750EX FMT imaging

BACKGROUND

In previous work, we demonstrated the presence of hydroxyapetite (type II microcalcification), HAP, in triple negative MDA-MB-231 breast cancer cells. We used (18)F-NaF to detect these types of cancers in mouse models as the free fluorine, (18)F(-), binds to HAP similar to bone uptake. In this work, we investigate other bone targeting agents and techniques including (99m)Tc-MDP SPECT and Osteosense 750EX FMT imaging as alternatives for breast cancer diagnosis via targeting HAP within the tumor microenvironment.

METHODS

Thirteen mice were injected subcutaneously in the right flank with 10(6) MDA-MB-231 cells. When the tumor size reached ~0.6 cm(3), mice (n=9) were injected with ~37 MBq of (99m)Tc-MDP intravenously and then imaged one hour later in a NanoSPECT/CT or injected intravenously with 4 nmol/g of Osetosense 750EX and imaged 24 hours later in an FMT (n=4). The imaging probe concentration in the tumor was compared to that of muscle. Following SPECT imaging, the tumors were harvested, sectioned into 10 μm slices, and underwent autoradiography or von Kossa staining to correlate (99m)Tc-MDP binding with HAP distribution within the tumor. The SPECT images were normalized to the injected dose and regions-of-interest (ROIs) were drawn around bone, tumor, and muscle to obtain the radiotracer concentration in these regions in units of percent injected dose per unit volume. ROIs were drawn around bone and tumor in the FMT images as no FMT signal was observed in normal muscle.

RESULTS

Uptake of (99m)Tc-MDP was observed in the bone and tumor with little or no uptake in the muscle with concentrations of 11.34±1.46 (mean±SD), 2.22±0.95, and 0.05±0.04%ID/cc, respectively. Uptake of Osteosense 750EX was also observed in the bone and tumor with concentrations of 0.35±0.07 (mean±SD) and 0.04±0.01picomoles, respectively. No FMT signal was observed in the normal muscle. There was no significant difference in the bone-to-tumor ratio between the two modalities (5.1±2.3 for SPECT and 8.8±2.2 for FMT) indicating that there is little difference in tumor uptake between these two agents.

CONCLUSION

This study provides evidence of the accessibility of HAP within the breast tumor microenvironment as an in vivo imaging target for bone-seeking agents. SPECT imaging using (99m)Tc-MDP can be rapidly translated to the clinic. FMT imaging using Osteosense 750EX is not currently approved for clinical use and is limited to animal research.

Preparation and characterization of a novel aspirin derivative with anti-thrombotic and gastric mucosal protection properties

The use of acetylsalicylic acid (ASP) is limited by its adverse effects, especially the effect on the gastric mucosa. To address this problem, we synthesized a derivative form of ASP, prepared by modification of ASP with nano-hydroxyapatite (a kind of inorganic particle containing Ca(2+)). The derivative was named Ca-ASP. Structural study showed that Ca-ASP was a kind of carboxylate containing intramolecular hydrogen bonds. Rats given a high dose of Ca-ASP (5 mmol per kg body weight) showed similar anti-thrombotic activity as those given the same dose of ASP, but had much lower gastric mucosal damage than ASP (UI: 2 versus UI: 12.5). These rats also showed reduced expression of COX-2, but their COX-1 expression was similar to that of control rats, but significantly higher than that of ASP-administered rats. Furthermore, the level of prostaglandin E2 (PGE2) was up-regulated in Ca-ASP-administered rats compared to ASP-administered rats. Taken together, the results showed that Ca-ASP possessed similar antithrombotic activity as ASP but without the side effect associated with ASP, and the underlying mechanism may center on inhibiting COX-2 without inhibiting COX-1, and thus favouring the production of PGE2, the prostaglandin that plays a vital role in the suppression of platelet aggregation and thrombosis, as well as in the repair of gastric damage.

An Approach to Breast Cancer Diagnosis via PET Imaging of Microcalcifications Using (18)F-NaF

Current radiologic methods for diagnosing breast cancer detect specific morphologic features of solid tumors or any associated calcium deposits. These deposits originate from an early molecular microcalcification process of 2 types: type 1 is calcium oxylate and type II is carbonated calcium hydroxyapatite. Type I microcalcifications are associated mainly with benign tumors, whereas type II microcalcifications are produced internally by malignant cells. No current noninvasive in vivo techniques are available for detecting intratumoral microcalcifications. Such a technique would have a significant impact on breast cancer diagnosis and prognosis in preclinical and clinical settings. (18)F-NaF PET has been used solely for bone imaging by targeting the bone hydroxyapatite. In this work, we provide preliminary evidence that (18)F-NaF PET imaging can be used to detect breast cancer by targeting the hydroxyapatite lattice within the tumor microenvironment with high specificity and soft-tissue contrast-to-background ratio while delineating tumors from inflammation.

METHODS

Mice were injected with approximately 10(6) MDA-MB-231 cells subcutaneously and imaged with (18)F-NaF PET/CT in a 120-min dynamic sequence when the tumors reached a size of 200-400 mm(3). Regions of interest were drawn around the tumor, muscle, and bone. The concentrations of radiotracer within those regions of interest were compared with one another. For comparison to inflammation, rats with inflamed paws were subjected to (18)F-NaF PET imaging.

RESULTS

Tumor uptake of (18)F(-) was significantly higher (P < 0.05) than muscle uptake, with the tumor-to-muscle ratio being about 3.5. The presence of type II microcalcification in the MDA-MB-231 cell line was confirmed histologically using alizarin red S and von Kossa staining as well as Raman microspectroscopy. No uptake of (18)F(-) was observed in the inflamed tissue of the rats. Lack of hydroxyapatite in the inflamed tissue was verified histologically.

CONCLUSION

This study provides preliminary evidence suggesting that specific targeting with (18)F(-) of hydroxyapatite within the tumor microenvironment may be able to distinguish between inflammation and cancer.

Osteotropic cancer diagnosis by an osteocalcin inspired molecular imaging mimetic

BACKGROUND

Although microcalcifications of hydroxyapatite can be found in both benign and malignant osteotropic tumors, they are mostly seen in proliferative lesions, including carcinoma. The aim of this present study is to develop a molecular imaging contrast agent for selective identification of hydroxyapatite calcification in human osteotropic tumor tissues ex vivo and in human osteosarcoma cells in vitro.

METHODS

A bioinspired biomarker, hydroxyapatite binding peptide (HABP), was designed to mimic natural protein osteocalcin property in vivo. A fluorescein isothiocyanate dye conjugated HABP (HABP-19) was utilized to characterize hydroxyapatite on human osteotropic tumor tissue sections ex vivo and to selectively image hydroxyapatite calcifications in human osteosarcoma cells in vitro.

RESULTS

Using a HABP-19 molecular imaging probe, we have shown that it is possible to selectively image hydroxyapatite calcifications in osteotropic cancers ex vivo and in human SaOS-2 osteosarcoma cells in vitro.

CONCLUSION

Hydroxyapatite calcifications were selectively detected in osteotropic tissues ex vivo and in the early stage of the calcification process of SaOS-2 human osteosarcoma in vitro using our HABP-19 molecular imaging probe. This new target-selective molecular imaging probe makes it possible to study the earliest events associated with hydroxyapatite deposition in various osteotropic cancers at the cellular and molecular levels.

GENERAL SIGNIFICANCE

It potentially could be used to diagnose and treat osteotropic cancer or to anchor therapeutic agents directing the local distribution of desired therapy at calcified sites.