Estrogen receptor alpha and androgen receptor are commonly expressed in well-differentiated liposarcoma.

BACKGROUND: Liposarcoma (LS) is the second-most common type of soft-tissue sarcoma. Despite advances in knowledge and treatment of this disease, there remains a need for more effective LS therapy. Steroid hormone receptors regulate metabolism in adipocytes. Estrogen receptor alpha (ER), progesterone receptor (PR), and androgen receptor (AR) have been implicated in the pathophysiology of other cancer types. We sought to comprehensively determine temporal expression patterns of these receptors in LS. METHODS: We analyzed 561 histologically subtyped LS specimens from 354 patients for expression of ER, PR, and AR by immunohistochemistry (IHC) using diagnostic-grade reagents and protocols. The fractions of positively stained tumor cells were scored within each specimen. IHC scores were compared across LS subtypes using the Kruskal-Wallis test, and subtypes were compared using Dunn's post-hoc test. Ages of patients with receptor-positive vs. -negative LS were compared by t-test. Genders and races were compared for hormone receptor positivity using Fisher's exact test and Chi-square analysis, respectively. Recurrence-free survival was compared between receptor-positive and negative patients by log-rank test. p< 0.05 was considered significant. RESULTS: ER and AR were frequently expressed in LS, while few tumors expressed PR. Most of the ER + and AR + samples were of the well-differentiated LS subtype. A smaller fraction of de-differentiated LS expressed ER or AR, but expression was common within well-differentiated regions of tumors histologically classified as de-differentiated LS. In LS specimens from patients who underwent multiple surgeries over time, receptor expression frequently changed over time, which may be attributable in part to intratumor heterogeneity, varying degrees of de-differentiation, and biopsy bias. ER and AR were frequently co-expressed. Receptor status was not significantly associated with gender or race, but AR and PR expression were associated with earlier age at diagnosis. Receptor expression was not associated with altered recurrence-free survival. CONCLUSIONS: ER and AR are commonly expressed in LS, particularly in well-differentiated tumors. These data warrant further functional study to determine receptor function in LS, and the potential efficacy of anti-hormone therapies for the treatment of patients with LS.

Analysis of prognostic factors impacting oncologic outcomes after neoadjuvant tyrosine kinase inhibitor therapy for gastrointestinal stromal tumors.

BACKGROUND: Management of gastrointestinal stromal tumors (GISTs) has been transformed with tyrosine kinase inhibitors (TKIs). While data on optimal duration of adjuvant imatinib remains elusive, guidelines for administration of neoadjuvant TKIs remain unknown. METHODS: Under an institutional review board-approved protocol, patients at our institution with a diagnosis of GIST treated with neoadjuvant TKIs and surgical resection were identified. Clinical and pathologic characteristics were obtained from medical records. RESULTS: Ninety-three patients underwent surgical resection after neoadjuvant TKI therapy; 41 had primary and 52 had recurrent/metastatic GIST. Median follow-up was 2.4 years. Median duration of neoadjuvant therapy was 315 (range 3-1,611) days for primary and 537 (range 4-3,257) days for recurrent/metastatic GIST (p = 0.001). Two-year, recurrence-free survival (RFS) was 85 and 44 % for primary and recurrent/metastatic disease, respectively, whereas 2-year overall survival (OS) was 97 % for primary and 73 % for recurrent/metastatic GIST. For primary GIST, duration of neoadjuvant therapy >365 days (p = 0.02) was associated with higher risk of recurrence on univariate analysis, whereas none of the clinicopathologic factors impacted OS. For recurrent/metastatic disease, disease progression was associated with a shorter OS (p = 0.001), but no factors were found to impact RFS. Lastly, when examining all patients, KIT mutations (p = 0.03) and multivisceral resection (p = 0.011) predicted shorter RFS. CONCLUSIONS: Neoadjuvant TKIs can be effectively used for the treatment of primary and recurrent/metastatic GIST. While duration of neoadjuvant therapy, KIT mutation status, and the need for multivisceral resection can help to predict higher risk for recurrence, progression on neoadjuvant TKIs can aid in selection of patients with recurrent/metastatic disease for surgical resection.

Staging soft tissue sarcoma: evolution and change.

Soft tissue sarcoma (STS) is an extremely heterogeneous group of rare tumors that share a putative mesenchymal cell origin. STS can occur in any soft tissue in the body, yet all share a common feature of primarily disseminating hematogenously, particularly to the lungs. Staging for STS is particularly useful in prognosis, design of effective multimodality treatment programs, and comparing treatment outcomes from different centers and different eras. The current iteration of AJCC STS staging includes Tumor, Grade, Node, and Metastasis with "a" indicating superficial and "b" indicating deep designations. Further opportunities to improve this process exist, particularly as molecular considerations become more apparent, and future evolution into an even more useful STS staging system can be anticipated.

Platelet-activating factor mediates MMP-2 expression and activation via phosphorylation of cAMP-response element-binding protein and contributes to melanoma metastasis.

Overexpression of cAMP-response element (CRE)-binding protein (CREB) and activating transcription factor (ATF) 1 contributes to melanoma progression and metastasis at least in part by promoting tumor cell survival and stimulating matrix metalloproteinase (MMP) 2 expression. However, little is known about the regulation of CREB and ATF-1 activities and their phosphorylation within the tumor microenvironment. We analyzed the effect of platelet-activating factor (PAF), a potent phospholipid mediator of inflammation, for its ability to activate CREB and ATF-1 in eight cultured human melanoma cell lines, and we found that PAF receptor (PAFR) was expressed in all eight lines. In metastatic melanoma cell lines, PAF induced CREB and ATF-1 phosphorylation via a PAFR-mediated signal transduction mechanism that required pertussis toxin-insensitive Galphaq protein and adenylate cyclase activity and was antagonized by a cAMP-dependent protein kinase A and p38 MAPK inhibitors. Addition of PAF to metastatic A375SM cells stimulated CRE-dependent transcription, as observed in a luciferase reporter assay, without increasing the CRE DNA binding capacity of CREB. Furthermore, PAF stimulated the gelatinase activity of MMP-2 by activating transcription and MMP-2 expression. MMP-2 activation correlated with the PAF-induced increase in the expression of an MMP-2 activator, membrane type 1 MMP. PAF-induced expression of pro-MMP-2 was causally related to PAF-induced CREB and ATF-1 phosphorylation; it was prevented by PAFR antagonist and inhibitors of p38 MAPK and protein kinase A and was abrogated upon quenching of CREB and ATF-1 activities by forced overexpression of a dominant-negative form of CREB. PAF-induced MMP-2 activation was also down-regulated by p38 MAPK and protein kinase A inhibitors. Finally, PAFR antagonist PCA4248 inhibited the development of A375SM lung metastasis in nude mice. This result indicated that PAF acts as a promoter of melanoma metastasis in vivo. We proposed that metastatic melanoma cells overexpressing CREB/ATF-1 are better equipped than nonmetastatic cells to respond to PAF within the tumor microenvironment.

Inhibition of platelet-derived growth factor receptor signaling restricts the growth of human breast cancer in the bone of nude mice.

PURPOSE: Bone is a common site for breast cancer metastasis. Platelet-derived growth factor (PDGF) and PDGF receptors (PDGFR) are involved in the regulation of bone resorption. This study examined the effects of STI571 (imatinib mesylate), which inhibits PDGFR tyrosine kinase signaling, on the growth of human breast cancer cells in the bone of nude mice with consequent osteolysis. EXPERIMENTAL DESIGN: Human breast cancer MDA-MB-435 cells were injected into the tibia of female nude mice. Two weeks later the mice were treated with p.o. and injected water (control), daily p.o. STI571, weekly injection of paclitaxel, or daily STI571, plus weekly paclitaxel, for up to 8 weeks. Growth of tumors in bones and osteolysis were monitored by digital radiography and tumors were collected for histochemical analysis. RESULTS: Mice treated with STI571 or STI571 plus paclitaxel had smaller bone tumors with less lytic bone destruction than did mice treated with water or paclitaxel alone. The results of treatment with paclitaxel plus STI571 did not differ from those with STI571 alone. Immunohistochemistry showed that PDGF-A, PDGF-B, PDGFRalpha, and PDGFRbeta were expressed in the bone tumors. STI571 treatment inhibited PDGFR phosphorylation in tumor cells and tumor-associated endothelial cells, coincident with increased apoptosis, reduced proliferation, and lower microvessel density in the tumors. CONCLUSIONS: Activated PDGFRs are expressed by endothelial and tumor cells in breast cancer tumors growing in the bone of nude mice. Interfering with PDGFR signaling may be an approach to control the progressive growth of breast cancer cells and thus reduce bone lysis.

Vascular endothelial growth factor expression promotes the growth of breast cancer brain metastases in nude mice.

Patients with breast cancer brain metastases cannot be cured and have a poor prognosis, with a median survival time of six months after diagnosis, despite developments in diagnostic and therapeutic modalities. In large part the progress in understanding the biology of breast cancer brain metastasis has been limited by the lack of suitable cell lines and experimental models. The objective of this study was to develop a reliable experimental model to study the pathogenesis of breast cancer brain metastases, using intra-internal carotid artery injection of breast cancer cells into nude mice. Brain metastasis-selected variant cells were recovered after three cycles of injection into the internal carotid artery of nude mice and harvest of brain metastases, resulting in variants termed MDA-231 BR1, -BR2 and -BR3. The metastasis-selected cells had increased potential for experimental brain metastasis and mice injected with these cells had significantly shorter mean survival than mice injected with the original cell line. Brain metastatic lesions of the selected variants contained significantly more CD31-positive blood vessels than metastases of the non-selected cell line. The variants selected from brain metastases released significantly more VEGF-A and IL-8 into culture supernatants than the original cell line, and more VEGF-A RNA when cultured in normoxic conditions. Mice injected with MDA-231 BR3 into the carotid artery were treated with the VEGF-receptor tyrosine kinase inhibitor PTK787/Z 222584. Oral administration of the inhibitor resulted in a significant decrease in brain tumor burden, reduced CD31-positive vessels in the brain lesions and incidence of PCNA positive tumor cells, and increased apoptosis in the tumor, as measured by TUNEL labeling. We conclude that elevated VEGF expression contributes to the ability of breast cancer cells to form brain metastases. Targeting endothelial cells with a VEGF-receptor specific tyrosine kinase inhibitor reduced angiogenesis and restricted the growth of the brain metastases.

Exposure of melanoma cells to dacarbazine results in enhanced tumor growth and metastasis in vivo.

PURPOSE: In recent years, the incidence of cutaneous melanoma has increased more than that of any other cancer. Dacarbazine is considered the gold standard for treatment, having a response rate of 15% to 20%, but most responses are not sustained. Previously, we have shown that short exposure of primary cutaneous melanoma cells to dacarbazine resulted in the upregulation of interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF). The purpose of the present study was to determine how long-term exposure of melanoma cells to dacarbazine would affect their tumorigenic and metastatic potential in vivo. MATERIALS AND METHODS: The primary cutaneous melanoma cell lines SB2 and MeWo were repeatedly exposed in vitro to increasing concentrations of dacarbazine, and dacarbazine-resistant cell lines SB2-D and MeWo-D were selected and examined for their ability to grow and metastasize in nude mice. RESULTS: The dacarbazine-resistant cell lines SB2-D and MeWo-D exhibited increased tumor growth and metastatic behavior in vivo. This increase could be explained by the activation of RAF, MEK, and ERK, which led to the upregulation of IL-8 and VEGF. More IL-8, VEGF, matrix metalloproteinase-2 (MMP-2), and microvessel density (CD-31) were found in tumors produced by SB2-D and MeWo-D in vivo than in those produced by their parental counterparts. No mutations were observed in BRAF. CONCLUSION: Our results have significant clinical implications. Treatment of melanoma patients with dacarbazine could select for a more aggressive melanoma phenotype. We propose that combination treatment with anti-VEGF/IL-8 or MEK inhibitors may potentiate the therapeutic effects of dacarbazine.

A fully human antimelanoma cellular adhesion molecule/MUC18 antibody inhibits spontaneous pulmonary metastasis of osteosarcoma cells in vivo.

PURPOSE: The melanoma cellular adhesion molecule, also known as MUC18, is highly expressed on several tumors, including bone sarcomas. The level of MUC18 expression has been found to correlate directly with tumor progression and metastatic potential. These observations have established MUC18 as a candidate mediator of tumor growth and metastasis, and suggest that blockade of MUC18 might be a potential target for immunotherapy against several MUC18-expressing tumors, including human bone sarcomas. EXPERIMENTAL DESIGN: To investigate whether blockade of MUC18 might be a potential target for immunotherapy against osteosarcoma, we have recently developed a fully human anti-MUC18 antibody, ABX-MA1. We studied the effect of ABX-MA1 on growth, adhesion, invasion, and metastasis of human osteosaroma cells both in vitro and in vivo. RESULTS: MUC18 was widely expressed on both osteosarcoma and Ewing's sarcoma cells. ABX-MA1 had no effect on the proliferation of osteosarcoma cells in vitro, nor did it significantly inhibit the growth of KRIB human osteosarcoma cells when they were orthotopically implanted into the tibias of nude mice. However, after 6 weeks, significantly fewer ABX-MA1-treated mice developed spontaneous pulmonary metastases than did IgG-treated control mice. Additionally, ABX-MA1 decreased the invasion of osteosarcoma cells through Matrigel-coated filters and disrupted homotypic adhesion between osteosarcoma cells and their heterotypic interaction with human vascular endothelial cells. CONCLUSIONS: Our findings demonstrate that MUC18 plays a central role in the metastasis of osteosarcoma and suggest that targeted inhibition of this antigen by ABX-MA1 may be a novel immunotherapeutic approach in the management of this tumor.

Selection of more aggressive variants of the gI101A human breast cancer cell line: a model for analyzing the metastatic phenotype of breast cancer.

In vivo models utilizing orthotopic injection of tumor cells into nude mice have proven valuable for the study of metastasis. However, breast cancers are among the more difficult of human tumors to grow in immunodeficient mice, with a relatively low tumor take. Fewer still develop spontaneous metastases. The injection of GI101A breast cancer cells into the mammary fatpad (mfp) produced lung metastases in 25% of tumor-bearing mice. Selecting cells from the lung metastases and recycling in vivo resulted in the isolation of a series of variant cell lines. These cell lines were tested for tumorigenicity and metastasis in nude mice following mfp injection compared with the original cell line, and in vitro expression of factors associated with the metastatic phenotype measured. The in vivo selected cell lines were more aggressive, with higher tumor take, faster local growth rate and increased incidence (> or = 85%) and extent of lung metastasis. However, the metastasis-selected variants showed no increases in expression of the growth factor receptors EGFR or HER-2, and the pro-angiogenic factors VEGF-A and IL-8. Immunohistochemistry of mfp tumors revealed no differences in microvessel density (counting CD-31 positive structures) and cell proliferation (PCNA-positive cells) comparing the GI101A line with selected variants. No TUNEL-positive cells were detected in the tumors of the metastasis-derived variant, with a small number of cells undergoing apoptosis detected in sections of GI101A tumors. In vitro, the metastasis-derived variants were found to have a more robust expression of phosphorylated PKB/Akt, with or without EGF or serum stimulation, suggesting an association between Akt activation and metastatic ability. This new series of isogenic cell lines may be valuable for identifying molecular mechanisms involved in the metastatic progression of breast cancer.

Dacarbazine causes transcriptional up-regulation of interleukin 8 and vascular endothelial growth factor in melanoma cells: a possible escape mechanism from chemotherapy.

The incidence of cutaneous malignant melanoma in the United States has increased more than any other cancer in recent years. Chemotherapy for metastatic melanoma is disappointing, there being anecdotal cases of complete remission. Dacarbazine (DTIC) is considered the gold standard for treatment, having a response rate of 15-20%, but most responses are not sustained. The mechanisms for the increased chemotherapeutic resistance of melanoma are unclear. The objective of this study was to determine the mechanisms by which melanoma cells escape the cytotoxic effect of DTIC. Here, we show that DTIC induced interleukin (IL)-8 and vascular endothelial growth factor (VEGF) protein overexpression and secretion via transcriptional up-regulation in the two melanoma cell lines SB-2 and MeWo. Luciferase activity driven by the IL-8 and VEGF promoters was up-regulated by 1.5-2- and 1.6-3.5-fold, respectively, in the SB2 and MeWo melanoma cell lines. The mitogen-activated protein kinase signal transduction pathway seemed to regulate at least partially the activation of IL-8, whereas it was not involved in VEGF promoter regulation. Electrophoretic mobility shift analysis analyses have revealed an increase in binding activity of activator protein 1 (c-Jun) and nuclear factor-kappaB after DTIC treatment for both melanoma cell lines. Metastatic melanoma cell lines secreting high levels of IL-8 and VEGF were more resistant to DTIC than early primary melanomas secreting low levels of the cytokines. In addition, transfection of the primary cutaneous melanoma SB-2 cells with the IL-8 gene rendered them resistant to the cytotoxic effect of the drug, whereas the addition of IL-8-neutralizing antibody to metastatic melanoma cells lowered their sensitivity to DTIC. Taken together, our data demonstrate that DTIC can cause melanoma cells to secrete IL-8 and VEGF, which might render them resistant to the cytotoxic effects of the drug. We propose that combination treatment with anti-VEGF/IL-8 agents may potentiate the therapeutic effects of DTIC.

Cellular adhesion pathways and metastatic potential of human melanoma.

Cellular adhesion molecules of the cadherin, integrin, and immunoglobulin superfamilies are important to both growth and metastasis of many cancers, including malignant melanoma. Malignant melanoma is an excellent model for studying these molecules, due in part to a sequential series of five defineable stages. As the malignant phenotype of melanoma cells changes from the noninvasive radial growth phase to the vertical growth phase, which has high metastatic potential, so does the repertoire of the cellular adhesion molecules expressed on the cells surface. The cellular adhesion molecule MCAM/MUC18 confers metastatic potential and increased tumorigenicity to melanoma cells. MCAM/MUC18 mediates homotypic and heterotypic adhesion between melanoma cells and endothelial cells, respectively. Both types of interaction may promote metastasis at different stages in the metastasis cascade. We developed a fully humanized antibody to MCAM/MUC18 (ABX-MA1) that blocked melanoma metastasis in vivo. Furthermore, ABX-MA1 blocked the homotypic interaction between melanoma cells and endothelial cells as well as the promoter and collagenase activity of MMP-2. During melanoma progression the loss of E-cadherin expression disrupts normal homeostasis in the skin by freeing melanoma cells from structural and functional regulation by keratinocytes. The loss of functional E-cadherin is parallelled by a gain in N-cadherin function that mediates homotypic interaction between melanoma cells, facilitates gap-junctional formation with fibroblasts and endothelial cells and promotes melanoma cell migration and survival. In addition, loss of E-cadherin may affect the beta-catenin/wnt signaling pathways, resulting in deregulation of genes involved in growth and metastasis. The integrin family member alpha(v)beta(3) is widely expressed on melanoma cells in the vertical growth phase. When alpha(v)beta(3) is expressed in melanoma cells in the radial growth phase, this integrin is associated with increased tumor growth in vivo. alpha(v)beta(3) may also promote melanoma invasion, through an interaction with MMP-2, and transendothelial migration, via a heterotypic melanomaendothelial cell interaction. This review summarizes recent knowledge on how changes in these adhesion molecules contribute to the acquisition of the metastatic phenotype in human melanoma.

Inhibition of platelet-derived growth factor-mediated proliferation of osteosarcoma cells by the novel tyrosine kinase inhibitor STI571.

PURPOSE: Osteosarcoma is an aggressive primary bone cancer characterized by expression of platelet-derived growth factor (PDGF) and its cognate receptor. Coexpression of the growth factor and receptor suggests their role in autocrine or paracrine growth mechanisms. It has been reported previously that STI571 has specific activity in inhibiting select tyrosine kinase receptors, including PDGF and c-Kit. Osteosarcomas express low levels of c-Kit but abundant levels of PDGF receptor (PDGFR). EXPERIMENTAL DESIGN: To investigate the potential of STI571 as therapy for osteosarcoma, we studied its effects on PDGF-mediated cell growth in vitro and in an in vivo mouse model. RESULTS: PDGF acted as a potent mitogen in a dose-dependent manner in two osteosarcoma cell lines. STI571 (1.0 micro M) inhibited both PDGFR-alpha and PDGFR-beta phosphorylation and the downstream phosphorylation targets extracellular signal-regulated kinase and Akt. STI571 also inhibited PDGF-mediated growth and induced apoptosis in vitro as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and terminal deoxynucleotidyl transferase-mediated nick end labeling staining. To study the effect of STI571 alone or in combination with Taxol in an in vivo model, an osteosarcoma cell line (KRIB) was transplanted into the tibia of athymic nude mice. Mice were treated with STI571 (50 mg/kg p.o. q M-F), Taxol (8 mg/kg i.p. weekly), or STI571 plus Taxol for 6 weeks. There was no significant difference in tumor size between treatment and control mice. Aberrant signaling pathways downstream of the PDGFR in the v-Ki-ras oncogene-transformed KRIB cell line may in part explain this finding. CONCLUSIONS: Our data demonstrate that STI571 inhibits PDGF-mediated growth and leads to apoptosis of osteosarcoma cells in vitro by selective inhibition of the PDGFR tyrosine kinase. The effectiveness of STI571 in our studies suggests targeting of PDGFRs as a novel treatment for osteosarcoma.