Drug resistance features and S-phase fraction as possible determinants for drug response in a panel of human ovarian cancer xenografts

Expression of resistance gene and prognosis of chemotherapy in primary epithelial ovarian cancer

The sensitivity of tumor cells to chemotherapy drugs may become attenuated accounts for various reasons. Reduced drug sensitivity may cause the failure of chemotherapy and affect the prognosis of patients with cancer. This study investigates the relationship between the expression levels of lung resistance protein (LRP) and placental glutathione S-transferase-P1 (GSTP1), the resistance of primary epithelial ovarian cancer (PEOC) to chemotherapy, and the prognosis of patients with platinum drug-resistant PEOC.Quantitative PCR (QT-PCR) was used to detect the mRNA level of the resistance genes LRP, GSTP1 in all tissue and cell lines.The expression levels of resistance gene (LRP, GSTP1) in PEOC were the highest, followed by borderline adenoma tissues, and the lowest levels found in benign tumor tissues, the difference of genes expression between different tissues was statistically significant; the difference between the expression rates and relative expression level of drug resistance genes was statistically significant in platinum sensitive group compare with the platinum resistant group. The difference between resistant gene negative-expression and positive-expression of chemotherapy efficiency, disease free survival time, and recurrence time were statistically significant. The resistant genes expression in the PEOC patients of the negative-group survival curves was higher than that in the positive group. With ascites non-cellular component (ANCC) stimulated SKOV3 cells, the cell proliferation inhibition rate (CPIR) increased, and with ANCC stimulated SKOV3/DDP, the expression of LRP and GSTP1 also increased.ANCC may promote the expression of drug resistance genes, and the expression of genes may predict the poorly prognosis of epithelial ovarian cancer.

DNA ploidy and S-phase fraction analysis in peritoneal carcinomatosis from ovarian cancer: correlation with clinical pathological factors and response to chemotherapy

Objective

We investigated the correlation between ploidy or S-phase fraction (SPF) and the clinical pathological characteristics of patients with peritoneal carcinomatosis from ovarian cancer. We also assessed their relation with the in vivo and in vitro response to several chemotherapeutic agents.

Patients and methods

Fifty-three patients with peritoneal carcinomatosis from ovarian cancer were enrolled. Frozen tumor tissue was dissociated by a detergent–trypsin method, and the resulting cell suspension was stained with RNase A and propidium iodide. Samples were then analyzed for ploidy and SPF by flow cytometry. Fresh tumor tissue was dissociated by enzymatic digestion, and cells were exposed to different concentrations of cisplatin, adriamycin, carboplatin, gemcitabine and taxol for 72 hours. In vitro drug sensitivity was then measured using the sulforhodamine B assay.

Results

No significant correlation was found between ploidy or SPF and patient characteristics, even though primary carcinomas were mainly hyperdiploid and more proliferative than recurrent tumors. SPF differed significantly among ploidy categories (P=0.01), and high SPF was associated with short-term survival (P=0.48). Patients with multiploid tumors were the most resistant to platinum-based chemotherapy, whereas those with hyperdiploid tumors were the most responsive. In vitro multiploid tumors were the least sensitive, while hypodiploid samples showed the highest sensitivity to the tested drugs. Sensitivity to adriamycin was significantly correlated with ploidy (P=0.03), whereas sensitivity to taxol was correlated with SPF (P=0.04).

Conclusion

Our results indicate that ploidy and SPF could facilitate the choice of therapy for patients with peritoneal carcinomatosis.

Prognostic significance of S-phase fractions in peritumoral invading zone analyzed by laser scanning cytometry in patients with high-grade glioma: A preliminary study

The predominant characteristic of malignant glioma is the presence of invading tumor cells in the peritumoral zone. Distinguishing between tumor cells and normal cells in a peritumoral lesion is challenging. Therefore, the aim of the present study was to investigate the cell-cycle phase measurements of fixed paraffin-embedded specimens from the peritumoral invading zone of high-grade gliomas using laser scanning cytometry. A total of 12 high-grade gliomas (2 anaplastic astrocytomas and 10 glioblastomas) were studied. The tumor core and peritumoral invading zone of each tumor specimen were investigated. Tissue sections (50 µm) from the paraffin blocks were deparaffinized, rehydrated and enzymatically disintegrated, and the cells in suspension were stained with propidium iodide and placed on microscope slides. A slight trend for an increased S-phase fraction in the peritumoral invading zone compared with the tumor core was observed (P=0.24). Additionally, there was a trend for a decrease in the overall survival time of patients with increasing peritumoral invading zone S-phase fraction (P=0.12). These data suggest that laser scanning cytometry is a powerful and clinically relevant tool for the objective analysis of the cell cycle in malignant gliomas.

GSTP1 arrests bladder cancer T24 cells in G0/G1 phase and up-regulates p21 expression

OBJECTIVE

GSTP1 over-expression was introduced into human bladder cancer T24 cells via the lentivirus system. The influence of GSTP1 on the proliferation and cell cycle of T24 cells as well as the potential mechanisms was investigated.

METHODS

The lentiviral vector GSTP1-pWPXL was constructed and transfected into T24 cells in the presence of Lipofectamine 2000. CCK8 assay and colony formation test were performed to explore the impact of GSTP1 on the proliferation of T24 cells. Ollowing PI staining, flow cytometry was done to detect the proportion of T24 cells in different phases. Western blot assay was conducted to detect the protein p21 expression.

RESULTS

When compared with control group, T24 cells with GSTP1 over-expression showed significant reduction in cell proliferation (P < 0.01) and they were arrested in G0/G1 phase. Western blot assay indicated that the p21 protein expression in T24 cells with GSTP1 over-expression was significantly higher than that in control group.

CONCLUSION

GSTP1 may inhibit the proliferation of T24 cells and arrest these cells in G0/G1 phase, which may be ascribed to the up-regulated expression of p21.

The inhibitory effects of extracellular ATP on the growth of nasopharyngeal carcinoma cells via P2Y2 receptor and osteopontin

Background

Nasopharyngeal carcinoma (NPC) is a common malignant tumor observed in the populations of southern China and Southeast Asia. However, little is known about the effects of purinergic signal on the behavior of NPC cells. This study analyzed the effects of ATP on the growth and migration of NPC cells, and further investigated the potential mechanisms during the effects.

Methods

Cell viability was estimated by MTT assay. Transwell assay was utilized to assess the motility of NPC cells. Cell cycle and apoptosis were detected by flow cytometry analysis. Changes in OPN, P2Y2 and p65 expression were assessed by western blotting analysis or immunofluorescence. The effects of ATP and P2Y2 on promoter activity of OPN were analyzed by luciferase activity assay. The binding of p65 to the promoter region of OPN was examined by ChIP assay.

Results

An MTT assay indicated that ATP inhibited the proliferation of NPC cells in time- and dose-dependent manners, and a Transwell assay showed that extracellular ATP inhibited the motility of NPC cells. We further investigated the potential mechanisms involved in the inhibitory effect of extracellular ATP on the growth of NPC cells and found that extracellular ATP could reduce Bcl-2 and p-AKT levels while elevating Bax and cleaved caspase-3 levels in NPC cells. Decreased levels of p65 and osteopontin were also detected in the ATP-treated NPC cells. We demonstrated that extracellular ATP inhibited the growth of NPC cells via p65 and osteopontin and verified that P2Y2 overexpression elevated the inhibitory effect of extracellular ATP on the proliferation of NPC cells. Moreover, a dual luciferase reporter assay showed that the level of osteopontin transcription was inhibited by extracellular ATP and P2Y2. ATP decreased the binding of p65 to potential sites in the OPN promoter region in NPC cells.

Conclusion

This study indicated that extracellular ATP inhibited the growth of NPC cells via P2Y2, p65 and OPN. ATP could be a promising agent serving as an adjuvant in the treatment of NPC.

Mechanism of cellular accumulation of an iridium(III) pentamethylcyclopentadienyl anticancer complex containing a C,N-chelating ligand

The effect of replacement of the N,N-chelating ligand 1,10-phenanthroline (phen) in the Ir(III) pentamethylcyclopentadienyl (Cp*) complex [(η(5)-Cp*)(Ir)(phen)Cl](+) (2) with the C,N-chelating ligand 7,8-benzoquinoline (bq) to give [(η(5)-Cp*)(Ir)(bq)Cl] (1) on the cytotoxicity of these Cp*Ir(III) complexes toward cancer cell lines was investigated. Complex 2 is inactive, similar to other Cp*Ir(III) complexes containing the N,N-chelating ligands. In contrast, a single atom change (C(-) for N) in the chelating N,N ligand resulted in potency in human ovarian carcinoma cisplatin-sensitive A2780 cells, and, strikingly, 1 is active in the cisplatin-resistant human breast cancer MCF-7 and A2780/cisR cells. Replacement of the N,N-chelating ligand with the C,N-chelating ligand gives rise to increased hydrophobicity, leading to higher cellular accumulation, higher DNA-bound iridium in cells and higher cytotoxicity. The pathways involved in cellular accumulation of 1 have been further explored and compared with conventional cisplatin. The results show that both energy-independent passive diffusion and energy-dependent transport play a role in accumulation of 1. Further results were consistent with involvement of p-glycoprotein, multidrug resistance-associated protein 1 and glutathione metabolism in the efflux of 1. In contrast, the internalization of 1 mediated by the endocytotic uptake pathway(s) seems less likely. Understanding the factors which contribute to the mechanism of cellular accumulation of this Ir(III) complex can now lead to the design of structurally similar metal complexes for antitumor chemotherapy.

Suramin inhibits the growth of nasopharyngeal carcinoma cells via the downregulation of osteopontin

Radiotherapy is the principal therapy for nasopharyngeal carcinoma (NPC) at early stages. A number of chemotherapeutic methods have been used to inhibit the progression of NPC at elevated stages. Suramin has been reported to inhibit the growth of certain tumor cells via various pathways. In the present study, we aimed to analyze the effects of suramin on the proliferation of NPC cells (CNE-2). Suramin was proved to demonstrate NPC cell growth-inhibiting effects both in a dose- and time-dependent manner. To determine the potential mechanisms of these effects, western blotting and flow cytometric analysis were performed. Suramin was found to have the potential to induce cell cycle arrest in S-phase CNE-2 cells. Additionally, we found that the OPN level may decrease in suramin-treated CNE-2 cells. The changes of certain apoptosis- and p-AKT-associated proteins possibly regulating the OPN expression were measured by western blotting. In conclusion, suramin may function as a potential agent for the adjunctive therapy of NPC.

Enhanced S100 calcium-binding protein P expression sensitizes human bladder cancer cells to cisplatin

OBJECTIVE

• To investigate the role of S100 calcium-binding protein P (S100P) in the gain of cis-diamminedichloroplatinum (II) (cisplatin) resistance in bladder cancer, having previously found, with cDNA microarrays using two pairs of parental (T24, KK47) and their cisplatin-resistant bladder cancer cell lines (T24/DDP10, KK47/DDP20), that S100P mRNA expression was significantly reduced in cisplatin-resistant cells.

MATERIALS AND METHODS

• S100P mRNA and protein expression levels were investigated by northern and western blot analyses, respectively. • Intracellular S100P localization was examined by immunocytochemistry and immunohistochemistry. • S100P over-expression, obtained by transfection with S100P expression plasmid, was used to investigate whether or not S100P affected cellular resistance to cisplatin.

RESULTS

• S100P mRNA showed increased expression by cisplatin stimulation in parental cell lines. • On the other hand, S100P mRNA and protein expression levels were markedly reduced in cisplatin-resistant cells. • The over-expression of S100P in resistant cells resulted in an increased sensitivity to cisplatin.

CONCLUSIONS

• In bladder cancer cells, S100P was expressed and localized mainly in the nucleus. • S100P expression was also involved in cisplatin sensitivity. • S100P might thus represent a molecular marker predicting cisplatin sensitivity and a molecular therapeutic target for cisplatin-based chemotherapy.

Radiolabeled 5-iodo-3'-O-(17beta-succinyl-5alpha-androstan-3-one)-2'-deoxyuridine and its 5'-monophosphate for imaging and therapy of androgen receptor-positive cancers: synthesis and biological evaluation

High levels of androgen receptor (AR) are often indicative of recurrent, advanced, or metastatic cancers. These conditions are also characterized by a high proliferative fraction. 5-Radioiodo-3'-O-(17beta-succinyl-5alpha-androstan-3-one)-2'-deoxyuridine 8 and 5-radioiodo-3'-O-(17beta-succinyl-5alpha-androstan-3-one)-2'-deoxyuridin-5'-yl monophosphate 13 target AR. They are also degraded intracellularly to 5-radioiodo-2'-deoxyuridine 1 and its monophosphate 20, respectively, which can participate in the DNA synthesis. Both drugs were prepared at the no-carrier-added level. Precursors and methods are readily adaptable to radiolabeling with various radiohalides suitable for SPECT and PET imaging, as well as endoradiotherapy. In vitro and in vivo studies confirm the AR-dependent interactions. Both drugs bind to sex hormone binding globulin. This binding significantly improves their stability in serum. Biodistribution and imaging studies show preferential uptake and retention of 8 and 13 in ip xenografts of human ovarian adenocarcinoma cells NIH:OVCAR-3, which overexpress AR. When these drugs are administered at therapeutic dose levels, a significant tumor growth arrest is observed.

Integrated genome-wide DNA copy number and expression analysis identifies distinct mechanisms of primary chemoresistance in ovarian carcinomas

PURPOSE

A significant number of women with serous ovarian cancer are intrinsically refractory to platinum-based treatment. We analyzed somatic DNA copy number variation and gene expression data to identify key mechanisms associated with primary resistance in advanced-stage serous cancers.

EXPERIMENTAL DESIGN

Genome-wide copy number variation was measured in 118 ovarian tumors using high-resolution oligonucleotide microarrays. A well-defined subset of 85 advanced-stage serous tumors was then used to relate copy number variation to primary resistance to treatment. The discovery-based approach was complemented by quantitative-PCR copy number analysis of 12 candidate genes as independent validation of previously reported associations with clinical outcome. Likely copy number variation targets and tumor molecular subtypes were further characterized by gene expression profiling.

RESULTS

Amplification of 19q12, containing cyclin E (CCNE1), and 20q11.22-q13.12, mapping immediately adjacent to the steroid receptor coactivator NCOA3, was significantly associated with poor response to primary treatment. Other genes previously associated with copy number variation and clinical outcome in ovarian cancer were not associated with primary treatment resistance. Chemoresistant tumors with high CCNE1 copy number and protein expression were associated with increased cellular proliferation but so too was a subset of treatment-responsive patients, suggesting a cell-cycle independent role for CCNE1 in modulating chemoresponse. Patients with a poor clinical outcome without CCNE1 amplification overexpressed genes involved in extracellular matrix deposition.

CONCLUSIONS

We have identified two distinct mechanisms of primary treatment failure in serous ovarian cancer, involving CCNE1 amplification and enhanced extracellular matrix deposition. CCNE1 copy number is validated as a dominant marker of patient outcome in ovarian cancer.

Integrated genome-wide DNA copy number and expression analysis identifies distinct mechanisms of primary chemoresistance in ovarian carcinomas

PURPOSE

A significant number of women with serous ovarian cancer are intrinsically refractory to platinum-based treatment. We analyzed somatic DNA copy number variation and gene expression data to identify key mechanisms associated with primary resistance in advanced-stage serous cancers.

EXPERIMENTAL DESIGN

Genome-wide copy number variation was measured in 118 ovarian tumors using high-resolution oligonucleotide microarrays. A well-defined subset of 85 advanced-stage serous tumors was then used to relate copy number variation to primary resistance to treatment. The discovery-based approach was complemented by quantitative-PCR copy number analysis of 12 candidate genes as independent validation of previously reported associations with clinical outcome. Likely copy number variation targets and tumor molecular subtypes were further characterized by gene expression profiling.

RESULTS

Amplification of 19q12, containing cyclin E (CCNE1), and 20q11.22-q13.12, mapping immediately adjacent to the steroid receptor coactivator NCOA3, was significantly associated with poor response to primary treatment. Other genes previously associated with copy number variation and clinical outcome in ovarian cancer were not associated with primary treatment resistance. Chemoresistant tumors with high CCNE1 copy number and protein expression were associated with increased cellular proliferation but so too was a subset of treatment-responsive patients, suggesting a cell-cycle independent role for CCNE1 in modulating chemoresponse. Patients with a poor clinical outcome without CCNE1 amplification overexpressed genes involved in extracellular matrix deposition.

CONCLUSIONS

We have identified two distinct mechanisms of primary treatment failure in serous ovarian cancer, involving CCNE1 amplification and enhanced extracellular matrix deposition. CCNE1 copy number is validated as a dominant marker of patient outcome in ovarian cancer.

Development and characterization of multidrug resistant human hepatocarcinoma cell line in nude mice

AIM: To establish a multidrug resistant (MDR) cell sub-line from the human hepatocarcinoma cell line (HepG2) in nude mice.

METHODS: HepG2 cell cultures were incubated with increasing concentrations of adriamycin (ADM) to develop an ADM-resistant cell subline (HepG2/ADM) with cross-resistance to other chemotherapeutic agents. Twenty male athymic BALB/c-nu/nu mice were randomized into HepG2/nude and HepG2/ADM/nude groups (10 in each group). A cell suspension (either HepG2 or HepG2/ADM) was injected subcutaneously into mice in each group. Tumor growth was recorded, and animals were sacrificed 4-5 wk after cell implantation. Tumors were prepared for histology, and viable tumor was dispersed into a single-cell suspension. The IC₅₀ values for a number of chemotherapeutic agents were determined by 2, 3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt (MTT) assay. Rhodamine-123 retention/efflux and the level of resistance-associated proteins were determined by flow cytometry. The mRNA expression of mdr1, mrp and lrp genes was detected using reverse transcriptase polymerase chain reaction (RT-PCR) in HepG2/nude and HepG2/ADM/nude groups.

RESULTS: The appearances of HepG2/nude cells were slightly different from those of HepG2/ADM/nude cells. Similar tumor growth curves were determined in both groups. A cross-resistance to ADM, vincristine, cisplatin and 5-fluorouracil was seen in HepG2/ADM/nude group. The levels of P-glycoprotein and multidrug resistance-associated proteins were significantly increased. The mRNA expression levels of mdr1, mrp and lrp were higher in HepG2/ADM/nude cells.

CONCLUSION: ADM-resistant HepG2 subline in nude mice has a cross resistance to chemotherapeutic drugs. It may be used as an in vivo model to investigate the mechanisms of MDR, and explore the targeted approaches to overcoming MDR.

Altered expression pattern of topoisomerase IIalpha in ovarian tumor epithelial and stromal cells after platinum-based chemotherapy

OBJECTIVE

The aim of this study was to evaluate the expression of topoisomerase IIalpha (TOP2A) in epithelial and stromal cells of ovarian cancer.

METHODS

TOP2A expression was analyzed prospectively in normal and tumor epithelial and adjacent stromal cells using quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) after laser microdissection (n = 38), RNA in situ hybridization (n = 13), and immunohistochemistry (n = 69).

RESULTS

TOP2A mRNA was detected by RNA in situ hybridization in all ovarian cancer samples, with stronger hybridization signals in tumor epithelial cells compared to adjacent stromal cells. The same expression pattern was found by immunohistochemistry (P = .0001). Very interestingly, specific change was found in recurrent ovarian cancer after platinum-based chemotherapy: TOP2A expression decreased in tumor epithelial cells of recurrent ovarian cancer compared to primary ovarian cancer (P = .056), whereas it increased in tumor-adjacent stromal cells in carboplatin-treated recurrent tumors compared to primary ovarian cancer (P = .023).

CONCLUSION

TOP2A mRNA and protein expression in ovarian cancer exhibits specific patterns in tumor epithelial and adjacent stromal cells, which are differentially modulated after platinum-based chemotherapy. These data support the recently discovered importance of the stromal compartment in tumor progression and suggest that tumor stromal cells might be relevant to the development of chemotherapy resistance in ovarian cancer.

Expression of P-glycoprotein, glutathione S-transferase-π, topoisomerase Ⅱ and lung resistance protein in cardiac carcinoma and their clinical significances

AIM: To investigate the expression of multidrug resistant proteins and their clinical significances in cardiac carcinoma tissues.

METHODS: The expression of P-glycoprotein (P-gp), glutathione S-transferase-p (GST-π), topoisomerase Ⅱ (Topo-Ⅱ) and lung resistance protein (LRP) in 69 patients with cardiac carcinoma were determined by SP immunohistochemistry,and the results were studied in correlation with clinicopathological data.

RESULTS: The positive rates of P-gp, GST-π, Topo-Ⅱ and LRP expression in cardiac carcinoma (49.2%, 75.4%, 68.1% and 58%, respectively) were all higher than those in the normal tissues (0, 30%, 20% and 0, respectively, all P < 0.01). The expression of P-gp was correlated with clinical staging (Ⅰ, Ⅱ vs Ⅲ, Ⅳ: 28.6% vs 58.3%, P < 0.05) and lymphatic metastasis (metastasis vs non-metastasis: 67.5% vs 24.1%, P < 0.01). A significant correlation was found between GST-π and differentiated degree (40%, 75.8% and 88.5% for high, moderate, and low differentiation, respectively, P < 0.05), clinical staging (Ⅰ, Ⅱ vs Ⅲ, Ⅳ: 57.1% vs 83.2%, P < 0.05) and lymphatic metastasis (metastasis vs non-metastasis: 87.5% vs 58.6%, P< 0.05). The level of Topo-Ⅱexpression was associated with differentiated degree (33.3%, 69.7%, and 80.7%, for high, moderate, and low differentiation, respectively, P < 0.01), but not with the clinical staging (P > 0.05) and lymphatic metastasis (P > 0.05). LRP expression was in correlation with the clinical staging (Ⅰ, Ⅱ vs Ⅲ, Ⅳ: 38% vs 66.6%, P < 0.05), and lymphatic metastasis (metastasis vs non-metastasis: 70.0% vs 41.4%, P < 0.05).

CONCLUSION: Primary multidrug resistance coexists in cardiac carcinoma. Combined determination of P-gp, GST-π, Topo-Ⅱand LRP is useful for predicting the chemosensitivities and optimizing the chemotherapy strategies.

Inhibitory effects of extracellular adenosine triphosphate on growth of esophageal carcinoma cells

AIM: To study the growth inhibitory effects of ATP on TE-13 human squamous esophageal carcinoma cells in vitro.

METHODS: MTT assay was used to determine the inhibition of proliferation of ATP or adenosine (ADO) on TE-13 cell line. The morphological changes of TE-13 cells induced by ATP or ADO were observed under fluorescence light microscope by acridine orange (AO)/ethidium bromide (EB) double stained cells. The internucleosomal fragmentation of genomic DNA was detected by agarose gel electrophoresis. The apoptotic rate and cell cycle after treatment with ATP or ADO were determined by flow cytometry.

RESULTS: ATP and ADO produced inhibitory effects on TE-13 cells at the concentration between 0.01 and 1.0 mmol/L. The IC50 of TE-13 cells exposed to ATP or ADO for 48 and 72 h was 0.71 or 1.05, and 0.21 or 0.19 mmol/L, respectively. The distribution of cell cycle phase and proliferation index (PI) value of TE-13 cells changed, when being exposed to ATP or ADO at the concentrations of 0.01, 0.1, and 1 mmol/L for 48 h. ATP and ADO inhibited the cell proliferation by changing the distribution of cell cycle phase via either G0/G1 phase (ATP or ADO, 1 mmol/L) or S phase (ATP, 0.1 mmol/L) arrest. Under light microscope, the tumor cells exposed to 0.3 mmol/L ATP or ADO displayed morphological changes of apoptosis. A ladder-like pattern of DNA fragmentation was obtained from TE-13 cells treated with 0.1-1 mmol/L ATP or ADO in agarose gel electrophoresis. ATP and ADO induced apoptosis of TE-13 cells in a dose-dependent manner at the concentration between 0.03 and 1 mmol/L. The maximum apoptotic rate of TE-13 cells exposed to ATP or ADO for 48 h was 16.63% or 16.9%, respectively.

CONCLUSION: ATP and ADO inhibit cell proliferation, arrest cell cycle, and induce apoptosis of TE-13 cell line.

Synergistic antitumor activity of capecitabine in combination with irinotecan

5-Fluorouracil (5-FU) and capecitabine alone and in combination with irinotecan/oxaliplatin are clinically active in the treatment of colorectal and other solid tumors. Studies of the antitumor activity and toxicity of capecitabine or irinotecan alone and in combination with each other, were compared with 5-FU and raltitrexed in human tumor xenografts of colorectal and squamous cell carcinoma of the head and neck using clinically relevant schedules. Antitumor activity and toxicity were evaluated in nude mice bearing human colon carcinomas of HCT-8 and HT-29 and in head and neck squamous cell carcinomas of A253 and FaDu xenografts using the maximum tolerable dose of single-agent capecitabine, 5-FU, or raltitrexed, or each of the drugs in combination with irinotecan. Mice were treated with capecitabine and irinotecan alone or in combination using 2 different schedules: (1) capecitabine orally once a day for 7 days and a single dose of irinotecan (50 mg/kg intravenously [I.V.]), with each drug alone or in combination, and (2) capecitabine orally 5 days a week for 3 weeks and irinotecan 50 mg/kg (I.V. injection) once a week for 3 weeks, with each drug alone or in combination. For comparative purposes, the antitumor activity of single-agent capecitabine, 5-FU, or raltitrexed, or each drug in combination with irinotecan was carried out at its maximum tolerated dose (MTD) using a 3-week schedule. Results indicated that HT-29 and A253 xenografts were de novo resistant (no cure) to capecitabine and irinotecan alone at the MTD, whereas HCT-8 and FaDu xenografts were relatively more sensitive, yielding 10%-20% cures. The combination of irinotecan/capecitabine was much more active than either drug alone against all 4 tumor models. The cure rates were increased from 0 to 20% in A253 and HT-29 xenografts and from 10%-20% to 80%-100% in HCT-8 and FaDu tumor xenografts, respectively. Irinotecan/capecitabine had clear advantage over irinotecan/5-FU and irinotecan/raltitrexed in efficacy and selectivity in that they were more active and less toxic. The extent of synergy with irinotecan/capecitabine appears to be tumor-dependent and independent of the status of p53 expression. The potential impact of the preclinical results on clinical practice for the use of these drugs in combination needs clinical validation.

Reduced growth, increased vascular area, and reduced response to cisplatin in CD13-overexpressing human ovarian cancer xenografts

PURPOSE

Expression of aminopeptidase N/CD13 can be detected in several solid tumor types. Thus far, the role of CD13 in ovarian cancer has not been studied. We have investigated the expression pattern and biological function of CD13 in ovarian cancer.

EXPERIMENTAL DESIGN

First, we studied the expression of CD13 in ovarian cancer tissue of 15 patients representing three different histological types (5 patients each) by immunohistochemistry. We then stably transfected the IGROV-1 human ovarian cancer cell line with a CD13 expression vector and examined the biological effect of CD13 in vitro and in vivo.

RESULTS

The expression of CD13 in ovarian cancer was associated with the histological subtype: CD13 expression in tumor cells was observed in 80-100% of the patients with a serous or mucinous carcinoma and in only 20% of the clear cell carcinoma patients. In all patients' tumor samples, CD13-positive blood vessels were present. CD13 overexpression in IGROV-1 cells did not affect in vitro cell growth and sensitivity to doxorubicin, cisplatin, or gemcitabine. CD13 overexpression reduced invasion in Matrigel, which appeared to be independent of the aminopeptidase activity of CD13. Furthermore, the growth rate of IGROV-1/CD13 xenografts was reduced. The area of the vessel lumens was enlarged in a small percentage of vessels in the CD13-overexpressing xenografts. In addition, the CD13-overexpressing tumors were less sensitive to cisplatin.

CONCLUSIONS

CD13 is expressed in tumor as well as endothelial cells in human ovarian cancer. Our results suggest that CD13 overexpression affects ovarian cancer growth, vascular architecture, and response to chemotherapy. Further elucidation of the mechanism of the observed effects of CD13 is warranted to better understand its role in the pathophysiology of ovarian cancer.

Therapeutic synergy between irinotecan and 5-fluorouracil against human tumor xenografts

PURPOSE

Although the combination of irinotecan and 5-Fluorouracil is clinically active, it is associated with significant toxicity and resistance. Studies were carried out to define the optimal dosage, sequence, and timing for the combination in mice bearing xenografted human tumors.

EXPERIMENTAL DESIGN

The maximum tolerated dose of irinotecan and 5-Fluorouracil in combination was determined in nude mice. Therapeutic efficacy against established human colon carcinoma xenografts, HCT-8 and HT-29, and human head and neck squamous cell carcinoma xenografts, FaDu and A253, was determined using the rugs individually, simultaneously, and in sequence with various intervals in between. Treatments were i.v. weekly x 4. Immunohistochemical and reverse transcription-PCR measurements of relevant drug-metabolizing enzymes, apoptosis-related proteins, cell cycle distribution, cyclin A, and S phase fraction expression were carried out and compared with the therapeutic outcome.

RESULTS

The maximum tolerated dose of irinotecan resulted in cure rates of 30% or less in all xenografts. No cures were achieved with FUra alone. Concurrent administration of irinotecan and FUra, or of FUra 24 h before irinotecan, resulted in cure rates of <20%, except for FaDu (60%). Administration of irinotecan 24 h before FUra resulted in the highest cure rates, 80% in HCT-8, 0% in HT-29, 100% in FaDu, and 10% in A253.

CONCLUSIONS

The optimal therapeutic synergy was achieved when irinotecan was administered 24 h before 5-Flurouracil. Sensitivity to this combination was associated with poor differentiation status, higher cyclin A index, recruitment of cells into S phase, and induction of Bax expression and apoptosis.

Cyclin E deregulation alters the biologic properties of ovarian cancer cells

We have previously shown that the low molecular weight (LMW) forms (trunk 1 and trunk 2) of cyclin E are biochemically hyperactive and induce G1/S progression in normal epithelial cells. Here we investigate the biologic consequences of LMW cyclin E expression in ovarian cancer cells. Using a panel of ovarian carcinoma tumors we find that cyclin E overexpression is invariably due to the presence of LMW forms and that expression of these forms appears to correlate with more advanced grade and stage of disease. Despite similar expression of p21 and p27, cyclin E overexpressing tumors have higher kinase function. Using an isogenic ovarian cancer model, we find that clones that overexpress the trunk 1 (T1) protein have a 10-fold increase in cyclin E kinase function, a 20% increase in S-phase fraction, a 10-15% decrease in doubling time and a 20% increase in colony formation compared to parental cells that express only the FL cyclin E protein. T1 clones were resistant to G1 arrest but more sensitive to cisplatin. Therefore, in ovarian tumors, the presence of LMW cyclin E forms confers altered biologic properties. Our data provides a potential mechanism for the poor prognosis of patients with LMW cyclin E expressing tumors.

Genetic alterations in ovarian cancer cells that might account for sensitivity to chemotherapy in patients

The cellular response to anticancer agent treatments is determined by many factors that could be altered in tumor cells. The induction of apoptosis of cancer cells is thought to be important for the overall response of these cells. Despite the introduction of new and potent anticancer agents, the survival rate for patients with ovarian cancer remains poor. In general ovarian cancer cells present a poor propensity to undergo apoptosis, which could be one of the reasons for this relatively poor response observed in the clinic. Induction of apoptosis is the result of activation and repression of pro- and antiapoptotic genes, which are regulated by complex mechanisms. Many cancer cells activate a "survival" program to escape disruption and allow propagation. In this review we have analyzed the role of genetic alterations observed in ovarian cancer cells in determining cellular response to drug treatment.

Mechanisms of cisplatin resistance in clear cell carcinoma of the ovary

Resistance of clear cell carcinoma (CCC) of the ovary to platinum-based chemotherapy is associated with a poor prognosis. However, the mechanism underlying the resistance of CCC to platinum has not yet been understood. We conducted the present study to clarify the mechanism of cisplatin (CDDP) resistance in CCC cells. Eleven CCC and 5 serous adenocarcinoma (SAC) cell lines were used in this study. The IC(50) to CDDP ranged from 1.3 to 18.0 microM for CCC cells and from 2.2 to 13.0 microM for SAC cells. There was no correlation between multidrug resistance-associated protein expression and the sensitivity to CDDP in CCC cells. In contrast, the doubling time for CCC cells was significantly longer than that for SAC cells (61.4 vs. 29.8 h). A significant reverse correlation between the S-phase fraction and the response to CDDP was observed (r = 0.647, p < 0.05). The present study suggests that the resistance of CCC to CDDP may be caused by low cell proliferation.

Extracellular nucleotides inhibit growth of human oesophageal cancer cells via P2Y(2)-receptors

Extracellular ATP is known to inhibit growth of various tumours by activating specific purinergic receptors (P2-receptors). Since the therapy of advanced oesophageal cancer is unsatisfying, new therapeutic approaches are mandatory. Here, we investigated the functional expression and potential antiproliferative effects of P2-purinergic receptors in human oesophageal cancer cells. Prolonged incubation of primary cell cultures of human oesophageal cancers as well as of the squamous oesophageal cancer cell line Kyse-140 with ATP or its stable analogue ATP gamma S dose-dependently inhibited cell proliferation. This was due to both an induction of apoptosis and cell cycle arrest. The expression of P2-receptors was examined by RT-PCR, immunocytochemistry, and [Ca(2+)](i)-imaging. Application of various extracellular nucleotides dose-dependently increased [Ca(2+)](i). The rank order of potency was ATP=UTP>ATP gamma S>ADP=UDP. 2-methylthio-ATP and alpha,beta-methylene-ATP had no effects on [Ca(2+)](i). Complete cross-desensitization between ATP and UTP was observed. Moreover, the phospholipase C inhibitor U73122 dose-dependently reduced the ATP triggered [Ca(2+)](i) signal. The pharmacological features strongly suggest the functional expression of G-protein coupled P2Y(2)-receptors in oesophageal squamous cancer cells. P2Y(2)-receptors are involved in the antiproliferative actions of extracellular nucleotides. Thus, P2Y(2)-receptors are promising target proteins for innovative approaches in oesophageal cancer therapy.

Induction of MRP5 and SMRP mRNA by adriamycin exposure and its overexpression in human lung cancer cells resistant to adriamycin

Acquired anticancer drug resistance in cancer cells is often a result of an increase in levels of the ATP binding cassette (ABC) transporters that export anticancer drugs from cancer cells, suggesting that anticancer drugs may induce genes that mediate drug resistance in cancer cells. In this study, the induction of anticancer drug transporter gene expression by Adriamycin was examined in human lung cancer cell lines. Increased expression of MDR1, MRP5 and SMRP mRNA was observed 48 hr after the initiation of Adriamycin exposure in human lung cancer PC-14 cells and cisplatin-resistant PC-14/CDDP cells, in a dose-dependent manner as measured by TaqMan real-time RT-PCR. The levels of MRP-1, MRP2 and LRP mRNA were not altered by Adriamycin exposure. The biologic functions of the MRP5 and SMRP genes have not been fully clarified. To elucidate the relationship between Adriamycin resistance and MRP5 and SMRP, mRNA levels of MRP5 and SMRP in Adriamycin-resistant cell lines were compared with the parental cells. Increased expression of MRP5 and SMRP mRNA was observed in all 3 cell lines (SBC-3/ADM, AdR MCF7 and K562/ADM) by Northern blot analysis and RNase protection assay. These results suggest that subacute exposure of lung cancer cells to Adriamycin induced MRP5 and SMRP and that long-term exposure with Adriamycin selected the MRP5- and SMRP-overexpressing lung cancer cells. MRP5 and SMRP is a candidate molecule for acquired Adriamycin resistance in addition to MDR1.