Development of an exosomal gene signature to detect residual disease in dogs with osteosarcoma using a novel xenograft platform and machine learning.

Osteosarcoma has a guarded prognosis. A major hurdle in developing more effective osteosarcoma therapies is the lack of disease-specific biomarkers to predict risk, prognosis, or therapeutic response. Exosomes are secreted extracellular microvesicles emerging as powerful diagnostic tools. However, their clinical application is precluded by challenges in identifying disease-associated cargo from the vastly larger background of normal exosome cargo. We developed a method using canine osteosarcoma in mouse xenografts to distinguish tumor-derived from host-response exosomal messenger RNAs (mRNAs). The model allows for the identification of canine osteosarcoma-specific gene signatures by RNA sequencing and a species-differentiating bioinformatics pipeline. An osteosarcoma-associated signature consisting of five gene transcripts (SKA2, NEU1, PAF1, PSMG2, and NOB1) was validated in dogs with spontaneous osteosarcoma by real-time quantitative reverse transcription PCR (qRT-PCR), while a machine learning model assigned dogs into healthy or disease groups. Serum/plasma exosomes were isolated from 53 dogs in distinct clinical groups ("healthy", "osteosarcoma", "other bone tumor", or "non-neoplastic disease"). Pre-treatment samples from osteosarcoma cases were used as the training set, and a validation set from post-treatment samples was used for testing, classifying as "osteosarcoma detected" or "osteosarcoma-NOT detected". Dogs in a validation set whose post-treatment samples were classified as "osteosarcoma-NOT detected" had longer remissions, up to 15 months after treatment. In conclusion, we identified a gene signature predictive of molecular remissions with potential applications in the early detection and minimal residual disease settings. These results provide proof of concept for our discovery platform and its utilization in future studies to inform cancer risk, diagnosis, prognosis, and therapeutic response.

Propranolol Sensitizes Vascular Sarcoma Cells to Doxorubicin by Altering Lysosomal Drug Sequestration and Drug Efflux.

Angiosarcoma is a rare cancer of blood vessel-forming cells with a high patient mortality and few treatment options. Although chemotherapy often produces initial clinical responses, outcomes remain poor, largely due to the development of drug resistance. We previously identified a subset of doxorubicin-resistant cells in human angiosarcoma and canine hemangiosarcoma cell lines that exhibit high lysosomal accumulation of doxorubicin. Hydrophobic, weak base chemotherapeutics, like doxorubicin, are known to sequester within lysosomes, promoting resistance by limiting drug accessibility to cellular targets. Drug synergy between the beta adrenergic receptor (ß-AR) antagonist, propranolol, and multiple chemotherapeutics has been documented in vitro, and clinical data have corroborated the increased therapeutic potential of propranolol with chemotherapy in angiosarcoma patients. Because propranolol is also a weak base and accumulates in lysosomes, we sought to determine whether propranolol enhanced doxorubicin cytotoxicity via antagonism of ß-ARs or by preventing the lysosomal accumulation of doxorubicin. ß-AR-like immunoreactivities were confirmed in primary tumor tissues and cell lines; receptor function was verified by monitoring downstream signaling pathways of ß-ARs in response to receptor agonists and antagonists. Mechanistically, propranolol increased cytoplasmic doxorubicin concentrations in sarcoma cells by decreasing the lysosomal accumulation and cellular efflux of this chemotherapeutic agent. Equivalent concentrations of the receptor-active S-(-) and -inactive R-(+) enantiomers of propranolol produced similar effects, supporting a ß-AR-independent mechanism. Long-term exposure of hemangiosarcoma cells to propranolol expanded both lysosomal size and number, yet cells remained sensitive to doxorubicin in the presence of propranolol. In contrast, removal of propranolol increased cellular resistance to doxorubicin, underscoring lysosomal doxorubicin sequestration as a key mechanism of resistance. Our results support the repurposing of the R-(+) enantiomer of propranolol with weak base chemotherapeutics to increase cytotoxicity and reduce the development of drug-resistant cell populations without the cardiovascular and other side effects associated with antagonism of ß-ARs.

5-HT serotonin receptors modulate mitogenic signaling and impact tumor cell viability.

Symptoms of depression are present in over half of all cancer patients, and selective serotonin reuptake inhibitor (SSRI) anti-depressant medications are prescribed to nearly a quarter of these individuals in order to cope with their disease. Previous studies have provided evidence that elevated serotonin (5-HT) and serotonin receptor levels may contribute to oncogenic progression, yet little is known regarding the mechanism by which this occurs. The data demonstrated that serotonin receptor mRNAs and proteins are expressed across diverse cancer types, and that serotonin stimulation of tumor cells activates oncogenic signaling mediators including components of the AKT, CREB, GSK3, and MAPK pathways. Selective pharmacological inhibition of the seven known classes of 5-HT receptors in sarcoma and breast cancer cells resulted in dose dependent decreases in tumor cell viability, activation of the p53 DNA damage pathway, suppression of MAPK activity, and significantly reduced tumor volume in an in ovo model. Based on a retrospective clinical analysis of 419 patients diagnosed with breast cancer, we discovered that use of SSRIs was associated with a 2.3-fold increase in tumor proliferation rates for late stage patients based on their Ki-67 index (P=0.03). These data provide evidence that serotonin signaling pathways, which treating oncologists often pharmacologically target to assist cancer patients to psychologically cope with their illness, activate signaling pathways known to promote tumor growth and survival.

Non-selective beta blockers inhibit angiosarcoma cell viability and increase progression free- and overall-survival in patients diagnosed with metastatic angiosarcoma.

Patients with metastatic angiosarcoma undergoing chemotherapy, radiation, and/or surgery experience a median progression free survival of less than 6 months and a median overall survival of less than 12 months. Given the aggressive nature of this cancer, angiosarcoma clinical responses to chemotherapy or targeted therapeutics are generally very poor. Inhibition of beta adrenergic receptor (ß-AR) signaling has recently been shown to decrease angiosarcoma tumor cell viability, abrogate tumor growth in mouse models, and decrease proliferation rates in preclinical and clinical settings. In the current study we used cell and animal tumor models to show that ß-AR antagonism abrogates mitogenic signaling and reduces angiosarcoma tumor cell viability, and these molecular alterations translated into patient tumors. We demonstrated that non-selective ß-AR antagonists are superior to selective ß-AR antagonists at inhibiting angiosarcoma cell viability. A prospective analysis of non- selective ß-AR antagonists in a single arm clinical study of metastatic angiosarcoma patients revealed that incorporation of either propranolol or carvedilol into patients' treatment regimens leads to a median progression free and overall survival of 9 and 36 months, respectively. These data suggest that incorporation of non-selective ß-AR antagonists into existing therapies against metastatic angiosarcoma can enhance clinical outcomes.

Beta-adrenergic receptors are expressed across diverse cancers.

Based largely on retrospective analyses and a handful of prospective case reports, pharmacological inhibition of the beta adrenergic receptors using beta blockers has shown clinical anti-cancer efficacy in reproductive cancers, as well as angiosarcoma and multiple myeloma. Because of the potential promise of beta blockers as an adjunct to standard anti-cancer therapy, it is imperative to identify other tumor types expressing beta adrenergic (ß-AR) receptors so future preclinical and clinical studies can be directed at the most promising tumor targets. We performed immunohistochemical detection of ß1-AR, ß2-AR, and ß3-AR across 29 of the most common human cancer types (389 tissues total) and 19 matching non-diseased controls (100 tissues total). Our analysis revealed all three ß-AR receptors were expressed most strongly in melanoma relative to other cancer types. Other malignancies that revealed relatively higher levels of ß-AR receptors were esophagus, pancreas, kidney, and lung cancers. Moreover, particular ß-AR receptors exhibited significant overexpression in tumor tissue relative to their matching normal tissue in urogenital/reproductive malignancies including breast, endometrium, ovarian, and urothelial cancer, as well as colon, lung, and thyroid cancer. This study identifies several cancer types expressing the ß-AR receptors which should be evaluated in future studies for susceptibility to beta blockade.

PD-1 and PD-L1 expression in bone and soft tissue sarcomas.

PD-1 and its ligands have been shown to play a significant role in evasion of malignant tumour cells from the immune system. Last year, the Unites States Food and Drug Administration (FDA) approved anti-PD-1 inhibitors for treatment of non-small cell lung carcinoma and recently expanded the use of immunotherapy for metastatic urothelial cell carcinoma and Hodgkin lymphoma. However, studies on expression of PD-1 and its ligand in malignant bone and soft tissue sarcoma are sparse. In this study, we evaluated PD-1 and PD-L1 expression on variants of liposarcomas and rhabdomyosarcomas, osteosarcomas and chondrosarcomas. Tissue microarrays (TMAs) for liposarcomas (well differentiated, myxoid/round cell, and pleomorphic), rhabdomyosarcomas (alveolar, embryonal, pleomorphic, and spindle cell), conventional osteosarcomas and chondrosarcomas were stained for PD-1 and PD-L1 antibodies. Adipose tissue, skeletal muscle, bone, osteochondroma and lipoma were used as control and benign counterparts. Western blot was performed to evaluate expression of PD-1 and PD-L1 in four sarcoma cell lines. Osteosarcomas, chondrosarcomas, and all variants of liposarcomas and rhabdomyosarcomas over-expressed PD-1 relative to normal tissue. Expression of PD-1 in rhabdomyosarcomas was associated with higher tumour stage. Only one case of pleomorphic liposarcoma, one case of pleomorphic rhabdomyosarcoma and two cases of alveolar rhabdomyosarcomas were positive for PD-L1. Normal adipose tissue, skeletal muscle, and bone were negative for both PD-1 and PD-L1 and lipomas and osteochondroma weakly expressed PD-1 but not PD-L1. Western blot confirmed the presence of PD-1 protein in all four sarcoma cell lines. Overall, our results showed cytoplasmic expression of PD-1 in the bone and soft tissue sarcomas, while PD-L1 was negative. Whether these data are an indication for effectiveness of immunotherapy in the management of malignant bone and soft tissue sarcomas remains to be elucidated.

Rho kinase proteins display aberrant upregulation in vascular tumors and contribute to vascular tumor growth.

BACKGROUND: The serine/threonine protein kinases ROCK1 and 2 are key RhoA-mediated regulators of cell shape and cytoskeletal dynamics. These proteins perform multiple functions in vascular endothelial cell physiology and are attractive targets for cancer therapy based on their roles as oncogenes and metastatic promoters. Given their critical functions in both of these processes, we hypothesized that molecular targeting of ROCK proteins would be exceedingly effective against vascular tumors such as hemangiomas and angiosarcomas, which are neoplasms composed of aberrant endothelial cells. METHODS: In this study, we compared ROCK1 and 2 protein expression in a large panel of benign and malignant vascular tumors to that of normal vasculature. We then utilized shRNA technology to knockdown the expression of ROCK1 and 2 in SVR tumor-forming vascular cells, and evaluated tumor size and proliferation rate in a xenograft model. Finally, we employed proteomics and metabolomics to assess how knockdown of the ROCK paralogs induced alterations in protein expression/phosphorylation and metabolite concentrations in the xenograft tumors. RESULTS: Our findings revealed that ROCK1 was overexpressed in malignant vascular tumors such as hemangioendotheliomas and angiosarcomas, and ROCK2 was overexpressed in both benign and malignant vascular tumors including hemangiomas, hemangioendotheliomas, hemangiopericytomas, and angiosarcomas. shRNA-mediated knockdown of ROCK2, but not ROCK1, in xenograft vascular tumors significantly reduced tumor size and proliferative index compared to control tumors. Proteomics and metabolomics analysis of the xenograft tumors revealed both overlapping as well as unique roles for the ROCK paralogs in regulating signal transduction and metabolite concentrations. CONCLUSIONS: Collectively, these data indicate that ROCK proteins are overexpressed in diverse vascular tumors and suggest that specific targeting of ROCK2 proteins may show efficacy against malignant vascular tumors.

Enhanced expression of Programmed cell death 1 (PD-1) protein in benign vascular anomalies.

Programmed cell death 1 (PD-1) and its ligands have been shown to play a significant role in evasion of malignant tumour cells from the immune system. Last year, the United States Food and Drug Administration (FDA) approved anti-PD-1 inhibitors for treatment of non-small cell lung carcinoma and recently has approved anti-PD-L1 blocker for treatment of metastatic urothelial cell carcinoma. However, the role that the immune system might have on benign tumours including vascular anomalies has received less attention. In this study, we evaluated PD-1 and PD-L1 expression on two benign vascular anomalies: infantile haemangiomas and venous malformations. Tissue microarrays (TMAs) from these two entities were stained for PD-1 and PD-L1 antibodies. Blood vessels from normal tissue were used as control. The endothelial cells in both infantile haemangioma and venous malformation showed high expression of PD-1 but were negative for PD-L1. Endothelial cells within the blood vessels in normal tissues were negative for both PD-1 and PD-L1. Our results showed over-expression of PD-1 in subsets of vascular anomalies, while PD-L1 was negative. This would raise the possibility of immunotherapy in benign vascular tumour when other options are exhausted.

Use of non-selective ß-blockers is associated with decreased tumor proliferative indices in early stage breast cancer.

Previous studies suggest beta-adrenergic receptor (ß-AR) antagonists (ß-blockers) decrease breast cancer progression, tumor metastasis, and patient mortality; however the mechanism for this is unknown. Immunohistochemical analysis of normal and malignant breast tissue revealed overexpression of ß1-AR and ß3-AR in breast cancer. A retrospective cross-sectional study of 404 breast cancer patients was performed to determine the effect of ß-blocker usage on tumor proliferation. Our analysis revealed that non-selective ß-blockers, but not selective ß-blockers, reduced tumor proliferation by 66% (p < 0.0001) in early stage breast cancer compared to non-users. We tested the efficacy of propranolol on an early stage breast cancer patient, and quantified the tumor proliferative index before and after treatment, revealing a propranolol-mediated 23% reduction (p = 0.02) in Ki67 positive tumor cells over a three-week period. The anti-proliferative effects of ß-blockers were measured in a panel of breast cancer lines, demonstrating that mammary epithelial cells were resistant to propranolol, and that most breast cancer cell lines displayed dose dependent viability decreases following treatment. Selective ß-blockers alone or in combination were not as effective as propranolol at reducing breast cancer cell proliferation. Molecular analysis revealed that propranolol treatment of the SK-BR-3 breast cancer line, which showed high sensitivity to beta blockade, led to a reduction in Ki67 protein expression, decreased phosphorylation of the mitogenic signaling regulators p44/42 MAPK, p38 MAPK, JNK, and CREB, increased phosphorylation of the cell survival/apoptosis regulators AKT, p53, and GSK3ß. In conclusion, use of non-selective ß-blockers in patients with early stage breast cancer may lead to decreased tumor proliferation.

Heterotypic mouse models of canine osteosarcoma recapitulate tumor heterogeneity and biological behavior.

Osteosarcoma (OS) is a heterogeneous and rare disease with a disproportionate impact because it mainly affects children and adolescents. Lamentably, more than half of patients with OS succumb to metastatic disease. Clarification of the etiology of the disease, development of better strategies to manage progression, and methods to guide personalized treatments are among the unmet health needs for OS patients. Progress in managing the disease has been hindered by the extreme heterogeneity of OS; thus, better models that accurately recapitulate the natural heterogeneity of the disease are needed. For this study, we used cell lines derived from two spontaneous canine OS tumors with distinctly different biological behavior (OS-1 and OS-2) for heterotypic in vivo modeling that recapitulates the heterogeneous biology and behavior of this disease. Both cell lines demonstrated stability of the transcriptome when grown as orthotopic xenografts in athymic nude mice. Consistent with the behavior of the original tumors, OS-2 xenografts grew more rapidly at the primary site and had greater propensity to disseminate to lung and establish microscopic metastasis. Moreover, OS-2 promoted formation of a different tumor-associated stromal environment than OS-1 xenografts. OS-2-derived tumors comprised a larger percentage of the xenograft tumors than OS-1-derived tumors. In addition, a robust pro-inflammatory population dominated the stromal cell infiltrates in OS-2 xenografts, whereas a mesenchymal population with a gene signature reflecting myogenic signaling dominated those in the OS-1 xenografts. Our studies show that canine OS cell lines maintain intrinsic features of the tumors from which they were derived and recapitulate the heterogeneous biology and behavior of bone cancer in mouse models. This system provides a resource to understand essential interactions between tumor cells and the stromal environment that drive the progression and metastatic propensity of OS.

Growth Attenuation of Cutaneous Angiosarcoma With Propranolol-Mediated ß-Blockade.

IMPORTANCE: Patients with stage T2 multilesion angiosarcomas of the scalp and face that are larger than 10 cm demonstrate a 2-year survival rate of 0%. To our knowledge, major therapeutic advances against this disease have not been reported for decades. Preclinical data indicate that blocking ß-adrenergic signaling with propranolol hydrochloride disrupts angiosarcoma cell survival and xenograft angiosarcoma progression. OBSERVATIONS: A patient presented with a ß-adrenergic-positive multifocal stage T2 cutaneous angiosarcoma (≥20 cm) involving 80% of the scalp, left forehead, and left cheek, with no evidence of metastasis. The patient was immediately administered propranolol hydrochloride, 40 mg twice a day, as his workup progressed and treatment options were elucidated. Evaluation of the proliferative index of the tumor before and after only 1 week of propranolol monotherapy revealed a reduction in the proliferative index of the tumor by approximately 34%. A combination of propranolol hydrochloride, 40 mg 3 times a day, paclitaxel poliglumex, 2 mg/m2 infused weekly, and radiotherapy during the subsequent 8 months resulted in extensive tumor regression with no detectable metastases. CONCLUSIONS AND RELEVANCE: Our data suggest that ß-blockade alone substantially reduced angiosarcoma proliferation and, in combination with standard therapy, is effective for reducing the size of the tumor and preventing metastases. If successful, ß-blockade could be the first major advancement in the treatment of angiosarcoma in decades.

Enrichment of the embryonic stem cell reprogramming factors Oct4, Nanog, Myc, and Sox2 in benign and malignant vascular tumors.

BACKGROUND: The "stem cell theory of cancer" states that a subpopulation of cells with stem cell-like properties plays a central role in the formation, sustainment, spread, and drug resistant characteristics of malignant tumors. Recent studies have isolated distinct cell populations from infantile hemangiomas that display properties equivalent to aberrant progenitor cells, suggesting that, in addition to malignant tumors, benign tumors may also contain a stem cell-like component. METHODS: In this study, the expression levels of the embryonic stem cell reprogramming factors Oct4, Nanog, Myc, Sox2, and Klf4 were examined via immunohistochemistry in a panel of 71 benign, borderline, and malignant vascular tumors including capillary hemangioma, cavernous hemangioma, granulomatous hemangioma, venous hemangioma, hemangioendothelioma, hemangiopericytoma, and angiosarcoma. Antigenicity for each protein was quantified based on staining intensity and percentage of tissue positive for each antigen, and subsequently compared to data obtained from two control tissue sets: 10 vascular tissues and a panel of 58 various malignant sarcomas. RESULTS AND DISCUSSION: With the exception of Myc (which was only present in a subset of benign, borderline, and malignant tumors), Oct4, Nanog, Sox2, and Klf4 were detectable at variable levels across both normal and diseased tissues. Semi-quantitative evaluation of our immunohistochemical staining revealed that protein expression of Oct4, Nanog, Myc, and Sox2, but not Klf4, was significantly increased in benign, borderline, and malignant vascular tumors relative to non-diseased vascular tissue controls. Interestingly, the enhanced levels of Oct4, Nanog, Myc, and Sox2 protein were approximately equivalent between benign, borderline, and malignant vascular tumors. CONCLUSIONS: These findings provide supporting evidence that enrichment for proteins involved in pluripotency is not restricted solely to malignant tumors as is suggested by the "stem cell theory of cancer", but additionally extends to common benign vascular tumors such as hemangiomas.

Epithelial cell adhesion molecule is expressed in a subset of sarcomas and correlates to the degree of cytological atypia in leiomyosarcomas.

Epithelial cell adhesion molecule (EpCAM) is a protein involved in cell-to-cell attachment and is considered to be strictly expressed in epithelial tissues and epithelial-derived tumors. Furthermore, EpCAM has been shown to be a negative prognostic marker for several carcinomas. In this study, we performed a genomic meta-analysis of gene expression profiles housed in the Cancer Cell Line Encyclopedia to demonstrate that EpCAM mRNA is expressed at low to moderate levels in certain sarcoma cell lines. We utilized immunohistochemical staining to confirm that the EpCAM protein is expressed in a subset of angiosarcomas and leiomyosarcomas and in all the investigated osteosarcomas. Finally, we conducted a statistical analysis of clinical data to demonstrate that EpCAM protein expression is significantly and directly correlated with the degree of cytological atypia in leiomyosarcomas. In conclusion, this data suggests that, contrary to conventional beliefs, EpCAM is expressed in a subset of sarcomas and is a negative prognostic marker for leiomyosarcomas.

A genomics approach to identify susceptibilities of breast cancer cells to "fever-range" hyperthermia.

BACKGROUND: Preclinical and clinical studies have shown for decades that tumor cells demonstrate significantly enhanced sensitivity to "fever range" hyperthermia (increasing the intratumoral temperature to 42-45°C) than normal cells, although it is unknown why cancer cells exhibit this distinctive susceptibility. METHODS: To address this issue, mammary epithelial cells and three malignant breast cancer lines were subjected to hyperthermic shock and microarray, bioinformatics, and network analysis of the global transcription changes was subsequently performed. RESULTS: Bioinformatics analysis differentiated the gene expression patterns that distinguish the heat shock response of normal cells from malignant breast cancer cells, revealing that the gene expression profiles of mammary epithelial cells are completely distinct from malignant breast cancer lines following this treatment. Using gene network analysis, we identified altered expression of transcripts involved in mitotic regulators, histones, and non-protein coding RNAs as the significant processes that differed between the hyperthermic response of mammary epithelial cells and breast cancer cells. We confirmed our data via qPCR and flow cytometric analysis to demonstrate that hyperthermia specifically disrupts the expression of key mitotic regulators and G2/M phase progression in the breast cancer cells. CONCLUSION: These data have identified molecular mechanisms by which breast cancer lines may exhibit enhanced susceptibility to hyperthermic shock.

Morphological restriction of human coronary artery endothelial cells substantially impacts global gene expression patterns.

Alterations in cell shape have been shown to modulate chromatin condensation and cell lineage specification; however, the mechanisms controlling these processes are largely unknown. Because endothelial cells experience cyclic mechanical changes from blood flow during normal physiological processes and disrupted mechanical changes as a result of abnormal blood flow, cell shape deformation and loss of polarization during coronary artery disease, we aimed to determine how morphological restriction affects global gene expression patterns. Human coronary artery endothelial cells (HCAECs) were cultured on spatially defined adhesive micropatterns, forcing them to conform to unique cellular morphologies differing in cellular polarization and angularity. We utilized pattern recognition algorithms and statistical analysis to validate the cytoskeletal pattern reproducibility and uniqueness of each micropattern, and performed microarray analysis on normal-shaped and micropatterned HCAECs to determine how constrained cellular morphology affects gene expression patterns. Analysis of the data revealed that forcing HCAECs to conform to geometrically-defined shapes significantly affects their global transcription patterns compared to nonrestricted shapes. Interestingly, gene expression patterns were altered in response to morphological restriction in general, although they were consistent regardless of the particular shape the cells conformed to. These data suggest that the ability of HCAECs to spread, although not necessarily their particular morphology, dictates their genomics patterns.

Targeting of beta adrenergic receptors results in therapeutic efficacy against models of hemangioendothelioma and angiosarcoma.

Therapeutic targeting of the beta-adrenergic receptors has recently shown remarkable efficacy in the treatment of benign vascular tumors such as infantile hemangiomas. As infantile hemangiomas are reported to express high levels of beta adrenergic receptors, we examined the expression of these receptors on more aggressive vascular tumors such as hemangioendotheliomas and angiosarcomas, revealing beta 1, 2, and 3 receptors were indeed present and therefore aggressive vascular tumors may similarly show increased susceptibility to the inhibitory effects of beta blockade. Using a panel of hemangioendothelioma and angiosarcoma cell lines, we demonstrate that beta adrenergic inhibition blocks cell proliferation and induces apoptosis in a dose dependent manner. Beta blockade is selective for vascular tumor cells over normal endothelial cells and synergistically effective when combined with standard chemotherapeutic or cytotoxic agents. We demonstrate that inhibition of beta adrenergic signaling induces large scale changes in the global gene expression patterns of vascular tumors, including alterations in the expression of established cell cycle and apoptotic regulators. Using in vivo tumor models we demonstrate that beta blockade shows remarkable efficacy as a single agent in reducing the growth of angiosarcoma tumors. In summary, these experiments demonstrate the selective cytotoxicity and tumor suppressive ability of beta adrenergic inhibition on malignant vascular tumors and have laid the groundwork for a promising treatment of angiosarcomas in humans.

Gene expression analysis reveals marked differences in the transcriptome of infantile hemangioma endothelial cells compared to normal dermal microvascular endothelial cells.

BACKGROUND: Infantile hemangiomas are benign vascular tumors primarily found on the skin in 10% of the pediatric population. The etiology of this disease is largely unknown and while large scale genomic studies have examined the transcriptomes of infantile hemangioma tumors as a whole, no study to date has compared the global gene expression profiles of pure infantile hemangioma endothelial cells (HEMECs) to that of normal human dermal microvascular endothelial cells (HDMVECs). METHODS: To shed light on the molecular differences between these normal and aberrant dermal endothelial cell types, we performed whole genome microarray analysis on purified cultures of HEMECs and HDMVECs. We then utilized qPCR and immunohistochemistry to confirm our microarray results. RESULTS: Our array analysis identified 125 genes whose expression was upregulated and 104 genes whose expression was downregulated by greater than two fold in HEMECs compared to HDMVECs. Bioinformatics analysis revealed three major classifications of gene functions that were altered in HEMECs including cell adhesion, cell cycle, and arachidonic acid production. Several of these genes have been reported to be critical regulators and/or mutated in cancer, vascular tumors, and vascular malformations. We confirmed the expression of a subset of these differentially expressed genes (ANGPT2, ANTXR1, SMARCE1, RGS5, CTAG2, LTBP2, CLDN11, and KISS1) using qPCR and utilized immunohistochemistry on a panel of paraffin embedded infantile hemangioma tumor tissues to demonstrate that the cancer/testis antigen CTAG2 is highly abundant in vessel-dense proliferating infantile hemangiomas and with significantly reduced levels during tumor involution as vascular density decreases. CONCLUSION: Our data reveal that the transcriptome of HEMECs is reflective of a pro-proliferative cell type with altered adhesive characteristics. Moveover, HEMECs show altered expression of many genes that are important in the progression and prognosis of metastatic cancers.

Propranolol treatment of infantile hemangioma endothelial cells: A molecular analysis.

Infantile hemangiomas (IHs) are non-malignant, largely cutaneous vascular tumors affecting approximately 5-10% of children to varying degrees. During the first year of life, these tumors are strongly proliferative, reaching an average size ranging from 2 to 20 cm. These lesions subsequently stabilize, undergo a spontaneous slow involution and are fully regressed by 5 to 10 years of age. Systemic treatment of infants with the non-selective ß-adrenergic receptor blocker, propranolol, has demonstrated remarkable efficacy in reducing the size and appearance of IHs. However, the mechanism by which this occurs is largely unknown. In this study, we sought to understand the molecular mechanisms underlying the effectiveness of ß blocker treatment in IHs. Our data reveal that propranolol treatment of IH endothelial cells, as well as a panel of normal primary endothelial cells, blocks endothelial cell proliferation, migration, and formation of the actin cytoskeleton coincident with alterations in vascular endothelial growth factor receptor-2 (VEGFR-2), p38 and cofilin signaling. Moreover, propranolol induces major alterations in the protein levels of key cyclins and cyclin-dependent kinase inhibitors, and modulates global gene expression patterns with a particular affect on genes involved in lipid/sterol metabolism, cell cycle regulation, angiogenesis and ubiquitination. Interestingly, the effects of propranolol were endothelial cell-type independent, affecting the properties of IH endothelial cells at similar levels to that observed in neonatal dermal microvascular and coronary artery endothelial cells. This data suggests that while propranolol markedly inhibits hemangioma and normal endothelial cell function, its lack of endothelial cell specificity hints that the efficacy of this drug in the treatment of IHs may be more complex than simply blockage of endothelial function as previously believed.