Ganglioside GD2 as a therapeutic target for antibody-mediated therapy in patients with osteosarcoma.

BACKGROUND: Survival outcomes for patients with osteosarcoma have remained stagnant over the past 30 years. Targeting of ganglioside GD2, a glycosphingolipid on the cell surface of some tumors, with immunotherapy has resulted in improved outcomes for patients with neuroblastoma. In the current study, the expression pattern of GD2 was examined in osteosarcoma. METHODS: Immunohistochemistry was performed on osteosarcoma samples from patients at the time of initial biopsy, definitive surgery, and disease recurrence. The intensity and location of staining were scored. Cell-based enzyme-linked immunoadsorbent assay was performed on osteosarcoma cell lines to quantitate the level of GD2 expression. RESULTS: Forty-four osteosarcoma samples were evaluated by immunohistochemistry, including 8 samples from the initial biopsy, 28 samples from the definitive surgery, and 8 samples from the time of disease recurrence. GD2 was expressed on all 44 osteosarcoma samples. Osteosarcoma tissue obtained at the time of disease recurrence demonstrated a higher intensity of staining compared with samples obtained at initial biopsy and definitive surgery (P = .016). The majority of osteosarcoma cell lines expressed GD2 at higher levels than the neuroblastoma cell line BE(2)-C. CONCLUSIONS: Ganglioside GD2 is highly expressed on osteosarcomas. Clinical trials are needed to assess the efficacy of targeting GD2 in patients with osteosarcoma.

HER-2 expression is not prognostic in osteosarcoma; a Children's Oncology Group prospective biology study.

BACKGROUND: Since the initial reports of human epidermal growth factor receptor 2 (HER-2) expression as being prognostic in osteosarcoma, numerous small studies varying in the interpretation of the immunohistochemical (IHC) staining patterns have produced conflicting results. The Children's Oncology Group therefore embarked on a prospective biology study in a larger sample of patients to define in osteosarcoma the prognostic value of HER-2 expression using the methodology employed in the initial North American study describing an association between HER-2 expression and outcome. PROCEDURE: The analytic patient population was comprised of 149 patients with newly diagnosed osteosarcoma, 135 with localized disease and 14 with metastatic disease, all of whom had follow up clinical data. Paraffin embedded material from the diagnostic biopsy was stained with CB11 antibody and scored by two independent observers. Correlation of HER-2 IHC score and demographic variables was analyzed using a Fisher's exact test and correlation with survival using a Kaplan-Meier analysis. RESULTS: No association was found with HER-2 status and any of the demographic variables tested including the presence or absence of metastatic disease at diagnosis. No association was found between HER-2 status and either event free survival or overall survival in the patients with localized disease. CONCLUSION: HER-2 expression is not prognostic in osteosarcoma in the context of this large prospective study. HER-2 expression cannot be used as a basis for stratification of therapy. Identification of potential prognostic factors should occur in the context of large multi-institutional biology studies.

Impairment of methotrexate transport is common in osteosarcoma tumor samples.

Osteosarcoma does not respond well to conventional dose methotrexate but does respond to high-dose methotrexate. Previous work has indicated that this resistance may be due to impaired transport of methotrexate across the cell membrane. In this study, the PT430 competitive displacement assay was adapted to evaluate methotrexate transport in 69 high-grade osteosarcoma tumor samples. All samples studied were shown to have relatively impaired methotrexate transport by PT430 assay. Ninety-nine percent of the samples had less than 20% PT430 displacement by methotrexate. Eighty-eight percent exhibited displacement by methotrexate at less than 50% of the displacement by trimetrexate. The high frequency of impaired transport suggests the presence of decreased functionality of the reduced folate carrier protein. The overwhelming presence of impaired transport may explain why methotrexate needs to be given in high doses to be effective in osteosarcoma therapy and suggests that reduced folate carrier-independent antifolates should be explored.

Impairments in antifolate transport are common in retinoblastoma tumor samples.

BACKGROUND: Many patients with retinoblastoma have a genetic predisposition to cancer and external beam radiation therapy and alkylating agent chemotherapy may increase their risk of secondary malignancy. Identification of effective chemotherapy agents for retinoblastoma that are not associated with an elevated risk of secondary malignancy would be beneficial. PROCEDURE: Twenty-six specimens of fresh retinoblastoma tumor cells were studied in vitro with a PT430 competitive displacement assay. Differential displacement of the PT430 by methotrexate and not trimetrexate was considered indicative of a defect in reduced folate carrier (RFC)-mediated transport. Elevations in the accumulation of PT430 were considered indicative of dihydrofolate reductase (DHFR) amplification. RESULTS: In 9 of the 26 (35%) samples, displacement by methotrexate was less than half the displacement by trimetrexate indicative of a defect in the RFC. In 5 of the 26 (19%) samples, trimetrexate did not displace the PT430. In 7 of 26 (27%) samples, the peak PT430 accumulation was suggestive of DHFR overexpression. Overall 9 of 26 (35%) samples had no evidence of a transport defect or DHFR overexpression and would be anticipated to be potentially sensitive to methotrexate. In 15 of the 26 (58%), no defects existed in trimetrexate displacement or DHFR overexpression and would be anticipated to be potentially sensitive to trimetrexate. CONCLUSION: These results would support consideration of a phase II study to determine the effectiveness of trimetrexate for recurrent intra-ocular retinoblastoma.

The folate receptor alpha is frequently overexpressed in osteosarcoma samples and plays a role in the uptake of the physiologic substrate 5-methyltetrahydrofolate.

PURPOSE: Two major systems exist for folate cell entry: the reduced folate carrier (RFC) and the folate receptor (FR). Although defective RFC-mediated transport was frequently identified as a mechanism of methotrexate (MTX) resistance in osteosarcoma, the status of FR and its role in this disease are unknown. EXPERIMENTAL DESIGN: mRNA for FR alpha was measured in 107 osteosarcoma specimens using quantitative reverse transcription-PCR and was related to RFC expression. The effect of FR alpha overexpression on MTX resistance and natural folate uptake was studied using FR alpha non-expressing osteosarcoma 143B cells transfected with FR alpha cDNA in comparison with those transfected with sense or antisense RFC in the same genetic background. RESULTS: Eighty-four samples (78.5%) had detectable FR alpha mRNA, and 29.9% had higher levels than the ovarian cancer cell line SKOV-3. No correlation was found between mRNA levels of FR alpha and RFC (r(2)=0.002). FR alpha overexpression had minor effects on the transport of MTX and sensitivity to this drug. Among the transfected 143B sublines, only the 143B-FR alpha was able to uptake 5-methyltetrahydrofolate when the extracellular concentration was reduced to 2 nmol/L, which conferred a growth advantage in physiologic folate concentrations compared with vector-only-transfected cells. Importantly, this was not similarly achieved by RFC overexpression. CONCLUSIONS: This study suggests that FR alpha plays a role in the uptake of 5-methyltetrahydrofolate when the concentration gradient is insufficient for RFC-mediated transport. FR alpha overexpression is unlikely secondary to the decreased RFC expression in osteosarcoma.

An expression signature classifies chemotherapy-resistant pediatric osteosarcoma.

Osteosarcoma is the most common malignant bone tumor in children. Osteosarcoma patients who respond poorly to chemotherapy are at a higher risk of relapse and adverse outcome. Therefore, it was the aim of this study to identify prognostic factors at the time of diagnosis to characterize the genes predictive of poor survival outcome and to identify potential novel therapeutic targets. Expression profiling of 30 osteosarcoma diagnostic biopsy samples, 15 with inferior necrosis following induction chemotherapy (Huvos I/II) and 15 with superior necrosis following induction chemotherapy (Huvos III/IV), was conducted using Affymetrix U95Av2 oligonucleotide microarrays. One hundred and four genes were found to be statistically significant and highly differentially expressed between Huvos I/II and III/IV patients. Statistically significant genes were validated on a small independent cohort comprised of osteosarcoma xenograft tumor samples. Markers of Huvos I/II response predominantly were gene products involved in extracellular matrix (ECM) microenvironment remodeling and osteoclast differentiation. A striking finding was the significant decrease in osteoprotegerin, an osteoclastogenesis inhibitory factor. Additional genes involved in osteoclastogenesis and bone resorption, which were statistically different, include annexin 2, SMAD, PLA2G2A, and TGFbeta1. ECM remodeling genes include desmoplakin, SPARCL1, biglycan, and PECAM. Gene expression of select genes involved in tumor progression, ECM remodeling, and osteoclastogenesis were validated via quantitative reverse transcription-PCR in an independent cohort. We propose that osteosarcoma tumor-driven changes in the bone microenvironment contribute to the chemotherapy-resistant phenotype and offer testable hypotheses to potentially enhance therapeutic response.

Genetically transforming human osteoblasts to sarcoma: development of an osteosarcoma model.

Osteosarcoma is the most common primary malignant bone tumor in children and young adults. Although histologically defined by the presence of malignant osteoid, the tumor possesses lineage multipotency suggesting it could be derived from a cell anywhere on the differentiation pathway between a mesenchymal stem cell (MSC) and a mature osteoblast. To determine if preosteoblasts (pOB) could be the cell of origin differentiated MSCs were transformed with defined genetic elements. MSCs and pOB differentiated from the same MSCs were serially transformed with the oncogenes hTERT, SV40 large T antigen and H-Ras. Assays were performed to determine their tumorigenic properties, differentiation capacity and histologic appearance. When subcutaneously implanted in immunocompromised mice, cell lines derived from transformed MSC and pOB formed tumors in 4 weeks. In contrast to the transformed MSC, the pOB tumors demonstrated a histological appearance characteristic of osteosarcoma. The cell lines derived from the transformed pOB only had osteogenic and chondrogenic differentiation potential, but not adipogenic ones. However, the transformed MSC cells and standard osteosarcoma cell lines maintained their tri-lineage differentiation capacity. The inability of the transformed pOB cell line to undergo adipogenic differentiation, may suggest that osteosarcoma is derived from a cell intermediate in differentiation between an MSC and a pOB, with partial commitment to the osteoblastic lineage.

Phase I trial of the cyclin-dependent kinase inhibitor and protein kinase C inhibitor 7-hydroxystaurosporine in combination with Fluorouracil in patients with advanced solid tumors.

PURPOSE: Preclinical studies indicate that the cyclin-dependent kinase and protein kinase C inhibitor 7-hydroxystaurosporine (UCN-01) potentiates the cytotoxic effects of fluorouracil (FU). We designed a phase I clinical trial of FU in combination with UCN-01. PATIENTS AND METHODS: FU was administered as a weekly 24-hour infusion. Doses were escalated in successive cohorts according to a modified Fibonacci design. UCN-01 was administered once every 4 weeks, immediately after disconnection from FU, at a dose of 135 mg/m(2) over 72 hours in cycle 1 and 67.5 mg/m(2) over 36 hours in subsequent cycles. FU and UCN-01 pharmacokinetics were obtained on all patients, and thymidylate synthetase (TS) activity was measured in peripheral-blood mononuclear cells by reverse-transcriptase polymerase chain reaction. RESULTS: We escalated the weekly FU dose to 2,600 mg/m(2) in combination with once a month infusions of UCN-01. Dose-limiting toxicity included arrhythmia and syncope. Other toxicities included hyperglycemia, headache, and nausea and vomiting. The mean maximal plasma concentration of UCN-01 was 33.5 micromol/L. There was significant interpatient variability, which correlated with plasma concentrations of alpha-1 acid glycoprotein. FU was rapidly cleared and the dose had no effect on the area under the curve of UCN-01. Changes in TS expression were detectable in peripheral-blood mononuclear cells after administration of UCN-01 but did not correlate with toxicity or activity. We observed no objective response, although seven patients had stable disease, six of whom had received prior fluoropyrimidines. CONCLUSION: The combination of weekly infusions of FU and monthly UCN-01 can be administered safely and warrants further study in phase II trials. The recommended phase II dose of FU in combination with monthly UCN-01 is 2,600 mg/m(2).

Messenger RNA expression levels of CXCR4 correlate with metastatic behavior and outcome in patients with osteosarcoma.

PURPOSE: To determine if osteosarcoma cells express chemokine receptors and if their presence or absence relates to clinical features. EXPERIMENTAL DESIGN: Using fluorescent quantitative real-time PCR, the pattern of 17 chemokine receptors in 3 osteosarcoma cell lines and 68 osteosarcoma patient samples was analyzed. RESULTS: The expression of the chemokine receptors was generally low among the cell lines. In the high-grade osteosarcoma patient samples (n = 47), CXCR4 was the most commonly expressed (63%) and its expression level was inversely correlated to overall survival (P < 0.0001), event-free survival (P < 0.001), and metastasis-free survival (MFS; P = 0.002). There was also a correlation between the expression level of CXCR4 and the presence of metastasis at diagnosis (P = 0.002). CCR7 was expressed in 43% of the samples and its expression level was inversely correlated with overall survival (P = 0.03) and MFS (P = 0.007). CCR10 mRNA expression level was inversely correlated with MFS (P = 0.009). There was no association between the expression of CXCR4, CCR7, and CCR10. Of the 26 samples studied for stromal cell-derived factor-1 expression, 77% expressed it, but there was no correlation with the clinical variables or CXCR4 expression. Multivariate analysis revealed that mRNA expression level of CXCR4 was the only significant variable for overall survival (P = 0.0006), event-free survival (P = 0.004), and MFS (P = 0.025). CONCLUSIONS: These data suggest that CXCR4 could be useful as a prognostic factor and as a predictor of potential metastatic development in osteosarcoma. If further studies confirm that it is relevant to metastases in this disease, it could represent a new therapeutic target.

Elevated physiologic tumor pressure promotes proliferation and chemosensitivity in human osteosarcoma.

PURPOSE: This study investigates the effect of constitutively raised interstitial fluid pressure on osteosarcoma physiology and chemosensitivity. EXPERIMENTAL DESIGN: We did pressure and blood flow assessments at the time of open biopsy in patients with the diagnosis of high-grade osteosarcoma and correlated this to survival and chemotherapy-associated tumor necrosis. Osteosarcoma cell lines were then evaluated for proliferative and therapeutic indices in a replicated high-pressure environment. RESULTS: Sixteen osteosarcomas in vivo were assessed and exhibited elevated interstitial fluid pressures (mean 35.2 +/- SD, 18.6 mmHg). This was not associated with significantly impeded blood flow as measured by a Doppler probe at a single site (P < 0.12). Nonetheless, greater chemotherapy-associated necrosis and associated longer survival were seen in tumors with higher interstitial fluid pressures (P < 0.05). In vitro, cells undergo significant physiologic changes under pressure. Osteosarcoma cell lines grown in a novel hydrostatically pressurized system had variable cell line-specific growth proportional to the level of pressure. They were more proliferative as indicated by cell cycle analysis with more cells in S phase after 48 hours of pressurization (P < 0.01). There was a significant elevation in the cell cycle-related transcription factors E2F-1 (P < 0.03) and E2F-4 (P < 0.002). These changes were associated with increased chemosensitivity. Cells tested under pressure showed an increased sensitivity to cisplatin (P < 0.00006) and doxorubicin (P < 0.03) reminiscent of the increased chemotherapy-associated necrosis seen in tumors with higher interstitial fluid pressure in the clinical study. CONCLUSIONS: The results of this study suggest that cells in the in vivo pressurized environment are at a higher state of regenerative activity than is demonstrable in conventional cell culture systems. Variations in tumor interstitial fluid pressure have the potential to alter chemotherapeutic effects.

Methylthioadenosine phosphorylase gene deletions are common in osteosarcoma.

PURPOSE: Methylthioadenosine phosphorylase (MTAP) is an enzyme essential in the salvage of cellular adenine and methionine synthesis. The MTAP gene is located in the 9p21 chromosomal region and its loss is frequently associated with deletion of the tumor suppressor genes p15(INK4b) and p16(INK4a). The aim of this study was to investigate the frequency of molecular alterations in MTAP in osteosarcoma. EXPERIMENTAL DESIGN: Samples from patients with high-grade osteosarcoma (n = 96) and three osteosarcoma cell lines (HOS, SaOS-2, and U2OS) were analyzed. Genomic DNA was analyzed for MTAP gene deletions by PCR, RNA expression was measured by semiquantitative reverse transcription-PCR, and the protein levels were measured by immunohistochemistry. RESULT: Deletion of at least one MTAP exon was found in 36 of 96 (37.5%) osteosarcoma patient samples and in one of the three cell lines (HOS). In all cases in which an MTAP gene deletion was observed, there was absence of detectable mRNA and protein. Furthermore, in four osteosarcoma patients, an MTAP deletion which was not evident at diagnosis was detected in subsequent tumor samples. CONCLUSIONS: The MTAP gene is commonly deleted in osteosarcoma patient samples, leading to an absence of mRNA and protein expression; these results indicate that inhibitors of de novo purine synthesis or methionine depletion may be effective as treatments for osteosarcoma patients whose tumors fail to express MTAP.

Sequence alterations in the reduced folate carrier are observed in osteosarcoma tumor samples.

High-dose methotrexate is a standard component of therapy for high-grade osteosarcoma. Its effectiveness may be limited by intrinsic and acquired resistance. Decreased reduced folate carrier (RFC) expression has been shown in approximately half of osteosarcomas at diagnosis. Mutations and polymorphisms in the RFC gene have been reported in various cell lines. The purpose of this study was to investigate sequence alterations in the RFC gene in osteosarcoma tumor samples. The entire coding region of the RFC gene in samples from 162 osteosarcoma patients was screened by DNA single-stranded conformational polymorphism, followed by direct sequencing of any region with altered mobility. A previously identified polymorphism at cDNA position number 174 of RFC exon 2 was observed. Sixty-one samples (37.6%) were heterozygous with both A/G at this position (His(27)/Arg(27)), 52 samples (32.2%) were homozygous with G (Arg(27)), and 49 samples (30.2%) were homozygous with A (His(27)). Fifteen (9.2%) samples were identified with other RFC sequence variants in exon 2, none of which have been reported. The sequence variants in exon 2 included a G to A substitution at cDNA position 231, a G to A substitution at cDNA position 155, a C to T substitution at cDNA position 114, and a T to C substitution at cDNA position 104, resulting in a serine to asparagine substitution at amino acid 46, a glutamate to lysine substitution at amino acid 21, an alanine to valine substitution at amino acid 7, and a serine to proline substitution at amino acid 4, respectively. A deletion of A at cDNA position 126 resulting in a frameshift was also observed. Some of these variants were observed in multiple samples. Eight samples had altered single-stranded conformational polymorphism patterns in exon 3 that were associated with nucleotide changes that altered the amino acid sequence. All of these RFC sequence variants appeared to be heterozygous. Heterozygous C/T and homozygous C also were observed at RFC cDNA position 790 in exon 3, which does not alter the amino acid coding sequence. This study shows that RFC sequence alterations are frequent in samples from osteosarcoma patients. Additional studies are under way to determine the clinical significance of these sequence alterations and their effect on methotrexate transport and resistance.

mRNA expression levels of E2F transcription factors correlate with dihydrofolate reductase, reduced folate carrier, and thymidylate synthase mRNA expression in osteosarcoma.

Previous studies have shown that decreased expression of the reduced folate carrier (RFC) and increased expression of dihydrofolate reductase (DHFR) are associated with intrinsic and acquired methotrexate resistance, respectively, in osteosarcoma (OS). It has also been shown in colorectal cancer that E2F-1 expression correlates with thymidylate synthase (TS) and, to a lesser extent, DHFR expression. To begin to investigate the regulation of DHFR and RFC expression in OS samples, mRNA expression of E2F-1 and E2F-4 were measured in OS tumor samples and related to DHFR, RFC, and TS mRNA expression. Using fluorescent quantitative real-time PCR, 112 human OS patient samples were investigated for potential E2F-1/E2F-4:DHFR, E2F-1/E2F-4:RFC, and E2F-1/E2F-4:TS correlations. The expression ranges for each gene are as follows: DHFR, 0.02-33.13 (median = 0.20); RFC, 0.02-229.13 (median = 1.91); TS, 0.01-9.99 (median = 0.15); E2F-1, 0.05-69.07 (median = 0.52); and E2F-4, 0.24-52.35 (median = 1.45). Spearman correlation coefficients (r(s)) for E2F-1:DHFR, E2F-1:RFC, E2F-1:TS, E2F-4:DHFR, E2F-4:RFC, and E2F-4:TS were calculated to be 0.53, 0.63, 0.60, 0.41, 0.58, and 0.33, respectively (P < 0.001). On the basis of this data, moderate correlations exist between E2F-1/E2F-4 and DHFR, RFC, and TS. These results suggest E2F-1/E2F-4 may play a role in the regulation of RFC expression, which has not been reported previously. The E2F transcription factors are also related to DHFR and TS expression in OS samples, suggesting a possible involvement in methotrexate resistance. Although E2F mRNA levels correlate with DHFR, RFC, and TS mRNA expression, additional experiments are necessary to determine the direct effects of these transcription factors and identify other proteins that may influence this relationship.

Insulin-like growth factor 1 receptor and response to anti-IGF1R antibody therapy in osteosarcoma.

BACKGROUND: Survival outcomes for patients with osteosarcoma (OS) have remained stagnant over the past three decades. Insulin-like growth factor 1 receptor (IGF1R) is over-expressed in a number of malignancies, and anti-IGF1R antibodies have and are currently being studied in clinical trials. Understanding the molecular aberrations which result in increased tumor response to anti-IGF1R therapy could allow for the selection of patients most likely to benefit from IGF1R targeted therapy. METHODS: IGF1R mRNA expression was assessed by RT PCR in OS patient primary tumors, cell lines, and xenograft tumors. IGF1R copy number was assessed by 3 approaches: PCR, FISH, and dot blot analysis. Exons 1-20 of IGF1R were sequenced in xenograft tumors and 87 primary OS tumors, and surface expression of IGF1R was assessed by flow cytometry. Levels of mRNA and protein expression, copy number, and mutation status were compared with tumor response to anti-IGF1R antibody therapy in 4 OS xenograft models. RESULTS: IGF1R mRNA is expressed in OS. Primary patient samples and xenograft samples had higher mRNA expression and copy number compared with corresponding cell lines. IGF1R mRNA expression, cell surface expression, copy number, and mutation status were not associated with tumor responsiveness to anti-IGF1R antibody therapy. CONCLUSIONS: IGF1R is expressed in OS, however, no clear molecular markers predict response to IGF1R antibody-mediated therapy. Additional pre-clinical studies assessing potential predictive biomarkers and investigating targetable molecular pathways critical to the proliferation of OS cells are needed.

Tumour interstitial fluid pressure may regulate angiogenic factors in osteosarcoma.

PURPOSE: We have previously shown that osteosarcomas have states of increased interstitial fluid pressure (IFP) which correlate with increased proliferation and chemosensitivity. In this study, we hypothesized that constitutively raised IFP in osteosarcomas regulates angiogenesis. MATERIALS AND METHODS: Sixteen patients with the clinical diagnosis of osteosarcomas underwent blood fl ow and IFP readings by the wick-in-needle method at the time and location of open biopsy. Vascularity was determined by capillary density in the biopsy specimens. We performed digital image analysis of immunohistochemical staining for CD31, VEGF-A, VEGF-C and TPA on paraffin-embedded tissue blocks of the biopsy samples. Clinical results were validated in a pressurised cell culture system. RESULTS: IFPs in the tumours (mean 33.5 +/- SD 17.2 mmHg) were significantly higher (P = 0.00001) than that in normal tissue (2.9 +/- 5.7 mmHg). Pressure readings were significantly higher in low vascularity tumours compared to high vascularity tumours (P <0.001). In the osteosarcoma cell lines, growth in a pressurised environment was associated with VEGF-A downregulation, VEGF-C upregulation and TPA upregulation. The reverse was seen in the OB cell lines. Growth in the HUVEC cell line was not significantly inhibited in a pressurised environment. Immunohistochemical assessment for VEGF-A (P = 0.01), VEGF-C (P = 0.008) and TPA (P = 0.0001) translation were consistent with the findings on PCR. CONCLUSION: Our data suggest that some molecules in angiogenesis are regulated by changes in IFP.

Decreased levels of UMP kinase as a mechanism of fluoropyrimidine resistance.

5-Fluorouracil (5-FU) continues to be widely used for treatment of gastrointestinal cancers. Because many tumors show primary or acquired resistance, it is important to understand the molecular basis underlying the mechanism of resistance to 5-FU. In addition to its effect on thymidylate synthase inhibition and DNA synthesis, 5-FU may also influence RNA metabolism. Our previous studies revealed that colorectal cancer cells resistant to bolus 5-FU (HCT-8/4hFU) showed significantly decreased incorporation of the drug into RNA. Resistance to bolus 5-FU was associated with lower expression of UMP kinase (UMPK), an enzyme that plays an important role in the activation of 5-FU to 5-FUTP and its incorporation into RNA. Activities of other 5-FU-metabolizing enzymes (e.g., thymidine kinase, uridine phosphorylase, thymidine phosphorylase, and orotate phosphoribosyltransferase) remained unchanged between sensitive and resistant cell lines. Herein, we show that UMPK down-regulation in 5-FU-sensitive cells (HCT-8/P) induces resistance to bolus 5-FU treatment. Moreover, HCT-8/4hFU cells are even more cross-resistant to treatment with 5-fluorouridine, consistent with the current understanding of 5-fluorouridine as a RNA-directed drug. Importantly, colorectal cancer hepatic metastases isolated from patients clinically resistant to weekly bolus 5-FU/leucovorin treatment exhibited decreased mRNA expression of UMPK but not thymidylate synthase or dihydropyrimidine dehydrogenase compared with tumor samples of patients not previously exposed to 5-FU. Our findings provide new insights into the mechanisms of acquired resistance to 5-FU in colorectal cancer and implicate UMPK as an important mechanism of clinical resistance to pulse 5-FU treatment in some patients.

Platelet-derived growth factor receptor as a prognostic marker and a therapeutic target for imatinib mesylate therapy in osteosarcoma.

The purpose of this review was to determine whether imatinib mesylate (STI571, Gleevec) has a role in the treatment of osteosarcoma. The expression of platelet-derived growth factor (PDGF) receptor and its ligand was examined in a panel of surgical specimens obtained from 54 osteosarcoma patients, and then the expression was compared with prognosis. The effects of imatinib mesylate on growth and molecular events in 10 patient-derived osteosarcoma cell cultures were investigated. Immunohistochemical studies demonstrated frequent expression of PDGF-AA (80.4%) and PDGF-alpha receptor (79.6%) and their correlation with inferior event-free survival (P < .05). PDGF-B-B and PDGF-beta-receptor expressions were also frequent (75.4% and 86%, respectively); however, statistically significant inferior event-free survival was not demonstrated (P = .15). In vitro studies demonstrated that imatinib mesylate had a variable cytotoxic effect on various osteosarcoma primary cultures, with an IC(50) of 5.6 microM to 9.5 microM, and blocked the PDGF-induced intracellular signal transduction as well as inhibition of downstream Akt phosphorylation. Mitogen-activated protein kinase (MAPK) was constitutively activated despite PDGF stimulation and imatinib mesylate treatment in 7 of 10 osteosarcoma cultures, perhaps explaining uncontrolled proliferation and relative unresponsiveness to imatinib. Imatinib mesylate could not be viewed as having a role as a single agent at current conventional doses for the treatment of osteosarcoma. These findings predicted activity in osteosarcoma clinical trials and suggested that in vitro model systems predict clinical behavior and that PDGF and its receptor expression could potentially be used for determining prognosis of osteosarcoma.

Tumor interstitial fluid pressure may regulate angiogenic factors in osteosarcoma.

We have previously shown that osteosarcomas (OS) have states of increased interstitial fluid pressure (IFP), which correlate with increased proliferation and chemosensitivity. In this study, we hypothesized that constitutively raised IFP in OS regulates angiogenesis. Sixteen patients with the clinical diagnosis of OS underwent blood flow and IFP readings by the wick-in-needle method at the time and location of open biopsy. Vascularity was determined by capillary density in the biopsy specimens. We performed digital image analysis of immunohistochemical staining for CD31, VEGF-A, VEGF-C, and TPA on paraffin-embedded tissue blocks of the biopsy samples. Clinical results were validated in a pressurized cell culture system. Interstitial fluid pressures in the tumors (mean 33.5 +/- SD 17.2 mmHg) were significantly higher (p = 0.00001) than that in normal tissue (2.9 +/- 5.7 mmHg). Pressure readings were significantly higher in low vascularity tumors compared to high vascularity tumors (p < 0.001). In the OS cell lines, growth in a pressurized environment was associated with VEGF-A downregulation, VEGF-C upregulation, and TPA upregulation. The reverse was seen in the OB cell line. Growth in the HUVEC cell line was not significantly inhibited in a pressurized environment. Immunohistochemical assessment for VEGF-A (p = 0.01), VEGF-C (p = 0.008), and TPA (p = 0.0001) translation were consistent with the findings on PCR. Our data suggests that some molecules in angiogenesis are regulated by changes in IFP.

Over-expression of parathyroid hormone Type 1 receptor confers an aggressive phenotype in osteosarcoma.

Osteosarcoma is the most common primary bone malignancy in children and is associated with rapid bone growth. Parathyroid hormone-related peptide (PTHrP) signaling via parathyroid hormone Type 1 receptor (PTHR1) is important for skeletal development and is involved in bone metastases in other tumors. The aim of this study was to investigate the status of PTHrP/PTHR1 and its possible role in osteosarcoma. In a preliminary screening, a higher level of PTHR1 mRNA, but not PTHrP, was found in 4 osteosarcoma xenografts as compared with 4 standard cell lines, or 5 patient derived cell lines (p < 0.05) using quantitative RT-PCR. It was therefore extended to 55 patient specimens, in which a significantly higher level of PTHR1 mRNA was detected in metastatic or relapsed samples than those from primary sites (p < 0.01). Cell behavior caused by PTHR1 overexpression was further studied in vitro using PTHR1 transfected HOS cell line as a model. Over-expression of PHTR1 resulted in increased proliferation, motility and Matrigel invasion without addition of exogenous PTHrP suggesting an autocrine effect. Importantly, the aggressiveness in PTHR1-expressing cells was completely reversed by RNAi mediated gene knockdown. In addition, PTHR1 over-expression led to delayed osteoblastic differentiation and upregulation of genes involved in extracellular matrix production, such as TGF-beta1 and connective tissue growth factor. When cocultured with bone marrow derived monocytes, PTHR1 transfected HOS cells induced a greater number of osteoclasts. This study suggests that PTHR1 over-expression may promote osteosarcoma progression by conferring a more aggressive phenotype, and forming a more favorable microenvironment.

FCGR2A polymorphism is correlated with clinical outcome after immunotherapy of neuroblastoma with anti-GD2 antibody and granulocyte macrophage colony-stimulating factor.

PURPOSE: Anti-GD2 murine IgG3 antibody 3F8 kills neuroblastoma cells by antibody-dependent cell-mediated cytotoxicity (ADCC). Granulocyte macrophage colony-stimulating factor (GM-CSF) enhances phagocyte-mediated ADCC. The differential affinity of the human FCGR polymorphic alleles for 3F8 may influence the effectiveness of antibody immunotherapy. PATIENTS AND METHODS: The entire cohort of high risk neuroblastoma patients (N = 136) treated on protocol using 3F8 and GM-CSF were the subjects of this analysis. Tumor response was measured by standard clinical tools plus sensitive molecular monitoring using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Polymorphic alleles of FCGR2A and FCGR3A were determined by PCR plus direct sequencing using genomic DNA samples obtained from marrow or blood of patients. RESULTS: FCGR2A (R/R) genotype correlated with progression-free survival for the entire cohort (P = .049) and for the subset of patients with no history of prior relapse (P = .023). FCGR2A (R/R) also correlated with marrow remission 2.5 months after treatment initiation: by histology (P = .021 and P = .036, for the entire cohort and the subset, respectively) and by qRT-PCR (P = .052 and P = .033, respectively). CONCLUSION: The favorable outcome associated with FCGR2A (R/R) genotype is consistent with the proposed role of FCGR2A and phagocyte-mediated ADCC in 3F8 plus GM-CSF immunotherapy.