In vitro interaction between ecteinascidin 743 (ET-743) and radiation, in relation to its cell cycle effects.

Ecteinascidin 743 (ET-743) is a new marine-derived agent with promising activity against a number of solid tumours. In four human tumour cell lines, the interaction between ET-743 and radiation was investigated in relation to the effects of ET-743 on the cell cycle, in vitro. Cell survival was measured based on quantitative staining of cellular protein by sulforhodamine B. A 24 h treatment with ET-743 before radiation resulted in a moderate increase in radiosensitivity in three out of four cell lines. Dose enhancement factors > or =1.8 were observed for concentrations resulting in 52, 46 and 30% cell kill in ECV304, H292 and CAL-27, respectively, whereas in A549 no radiosensitisation was observed (no significant increase in radiosensitivity). According to the combination index analysis, synergism was observed only in ECV304 and CAL-27 cells. A 24 h incubation with ET-743 resulted in a concentration-dependent G2/M block, which might explain the moderate radiosensitising effects in ECV304 and H292. The lack of radiosensitisation in A549 might be due to the S phase delay preceding the G2/M block at the moment of radiation, which only occurred in this cell line. In conclusion, ET-743 has moderate cell line-dependent radiosensitising properties; however, only when cytotoxic concentrations of ET-743 are used. In one of the four cell lines tested, no radiosensitisation was observed.

The radiosensitising effect of gemcitabine and the influence of the rescue agent amifostine in vitro.

In this study, the radiosensitising effect of different concentrations of gemcitabine and the combination of gemcitabine/radiotherapy with the rescue agent amifostine was investigated in different human tumour cell lines. The cells were treated with gemcitabine (0-8 nM) for 24 h prior to radiation (0-8 Gy). Amifostine (ami) and alkaline phosphatase (AP) were added 30 min before radiation. Cell survival was determined 7 or 8 days after radiation treatment by the sulforhodamine B (SRB) test. For ECV304 cells, the dose enhancement factor (DEF) varied from 1.39 to 2.98 after treatment with 1-6 nM gemcitabine. FaDu, H292, A549 and CAL-27 seemed to be less sensitive, with DEFs ranging from 1.02 to 2.67. These cells were also less sensitive to the cytotoxic effects of single-agent gemcitabine. Amifostine with AP clearly showed a protective effect in combination with gemcitabine/radiotherapy. In H292 cells, the protection factor (PF) of amifostine after treatment with gemcitabine and radiotherapy varied from 1.64 to 1.86. In ECV304 cells, the PF varied from 2.20 to 2.29. In conclusion, a clear concentration- and cell line-dependent radiosensitising effect of gemcitabine was observed in all cell lines. Amifostine with AP showed protection against the radiosensitising effect of gemcitabine. If the protection in vivo indeed occurs selectively in normal tissues, then amifostine could prevent or strongly minimise the increased toxicity resulting from the radiosensitising effect of the combination of gemcitabine and radiotherapy, without influencing the antitumour effect.

[Interactions of carboplatin, cisplatin, and ionizing radiation on a human cell line of ovarian cancer]. / Interactions entre le carboplatine, le cisplatine et les rayonnements ionisants dans une lignée cellulaire humaine de cancer ovarien.

AIM OF THE STUDY: Cisplatin (CDDP) and radiotherapy are frequently used concomitantly in the treatment of various malignant conditions. Because of its toxicity, cisplatin tends to be replaced by carboplatin (CBDCA) in several indications. Available data regarding the combined effects of cisplatin and carboplatin with ionising radiation are contradictory. MATERIALS AND METHODS: Various concentrations of cisplatin and carboplatin and various timing of association with radiation have been tested in vitro in a human ovarian cancer cell line. The parental cell line (AOvC-0) and a cisplatin-resistant stable subline (AOvC-CDDP/0) (De Pooter et al., Canc Res, 1991) were exposed to carboplatin (2.5, 5 and 10 M) and to CDDP (1, 2.5 and 5 M), 16 h and 4 h before and 4 h and 16 h after irradiation, respectively. Cell survival was evaluated by a classical clonogenic assay. RESULTS: Exposure of AOvC-0 to 5 M CBDCA and of AOvC-CDDP/0 to 10 M CBDCA, before or shortly after radiation exposure, increased cell lethality in a clear supra-additive way, with the highest DEF in the shoulder region of the survival curve and at radiation doses relevant to clinical radiotherapy. In the sensitive cell line, 5 M carboplatin resulted in an additional lethality equivalent to 4.5 Gy; in the resistant cells, 10 M carboplatin was equivalent to 3.6 Gy. Replacing carboplatin by cisplatin in an identical set-up demonstrated exclusively simple additivity (DEF = 1). CONCLUSION: These data suggest that carboplatin and cisplatin delivered at equitoxic doses interact with radiation in a different way and that, in the present set-up, only carboplatin enhanced the effects of radiation. Carboplatin might consequently be a better candidate than cisplatin in some concomitant combinations with radiotherapy.

Expression of bcl-2 in invasive and in situ carcinoma of the uterine cervix.

OBJECTIVE: The oncoprotein bcl-2 inhibits apoptosis. The purpose of this study was to assess the expression of bcl-2 in human cervical carcinoma and to correlate this with clinicopathologic parameters. STUDY DESIGN: Immunohistochemical staining for bcl-2 protein (MoAB clone 124) was performed on operative tissue specimens from 22 patients with carcinoma in situ of the cervix and from 137 patients with invasive cervical carcinoma (International Federation of Gynecology and Obstetrics stages I to IV). The immunoreactivity of bcl-2 was scored as positive (> or = 5% staining cells) or negative (< 5% staining cells). RESULTS: Eighty-two percent of in situ carcinomas and 61% of invasive cervical carcinomas were bcl-2 positive. Expression of bcl-2 was correlated to tumor stage (p < 0.001) and to presence of vascular (p < 0.005) or lymphatic tumor (p < 0.023) permeation. In univariate analysis there was a strong relationship between bcl-2 expression and overall survival (p < 0.001). In multivariate analysis bcl-2 expression (p < 0.001), International Federation of Gynecology and Obstetrics stage (p = 0.011), and presence of lymphatic permeation (p = 0.014) proved to be independent prognostic factors. CONCLUSIONS: Expression of bcl-2 is lost during tumor progression and is a strong prognostic parameter, suggesting that the regulation of apoptosis plays an important role in the behavior of cervical carcinomas. Better understanding of the mechanisms involved may lead to improved medical treatment strategies.

Elevated levels of the angiogenic cytokines basic fibroblast growth factor and vascular endothelial growth factor in sera of cancer patients.

The concentration of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) was determined in the serum of 90 untreated and 42 treated metastatic cancer patients, including patients with colorectal, breast, ovarian and renal carcinomas, with an enzyme-linked immunosorbent assay (ELISA). Levels higher than the 95th percentile of the concentrations of a control group, i.e. 7.5 pg ml(-1) for bFGF and 500 pg ml(-1) for VEGF, were identified as 'elevated'. One measurement during follow-up was included into the analysis per patient. For 19 treated patients, consecutive serum samples were analysed. Fifty-seven per cent of all untreated patients had elevated serum levels of one or both angiogenic factors. The fraction of patients with elevated serum levels of bFGF and/or VEGF was similar in the different tumour types. Agreement of bFGF levels and VEGF levels, classified in relation to their respective cut-off values, was present in 67% of all patients. Fifty-eight per cent of the patients with progressive disease during treatment compared with 15% of the patients showing response to treatment (chi-squared test P < 0.05) had elevated bFGF and/or VEGF serum levels. When consecutive serum samples were analysed, two-thirds of the patients showing progressive disease had increasing serum levels of the angiogenic factors compared with less than one-tenth of the patients showing response (chi-squared test P < 0.05). The lack of association between the serum bFGF and VEGF levels and the tumour type may suggest an aspecific host reaction responsible for solid tumour-related angiogenesis. The main determinants of the serum bFGF and VEGF concentration are the progression kinetics of the metastatic carcinomas.

Prognostic value of bcl-2 expression in patients with operable carcinoma of the uterine cervix.

AIM: To evaluate the patterns of bcl-2 expression in early stage cervical carcinoma; to compare bcl-2 expression with clinicopathological findings; and to assess its prognostic value. METHODS: Wertheim radical hysterectomy specimens from 76 patients (FIGO stages Ia-IIb) with untreated nonmetastatic invasive cervical carcinoma were studied. Expression of bcl-2 was detected immunohistochemically using a monoclonal antibody. A tumour was regarded as positive when more than 5% of the neoplastic cells exhibited bcl-2 immunoreactivity. RESULTS: Forty eight (63%) cervical carcinomas were scored as bcl-2 positive and 28 (37%) as bcl-2 negative. Most tumours showed heterogeneous cytoplasmic staining. Bc1-2 immunoreactivity did not correlate with tumour histology, tumour stage, presence of lymph node metastases, or involvement of the lymphovascular space. The five year survival rate for patients with bc1-2 negative tumours was 34% and was 71% for patients with bc1-2 positive tumours. On multiple regression analysis (Cox proportional hazards model), bc1-2 expression and vascular permeation were independent predictors of overall survival. CONCLUSIONS: Bcl-2 expression seems to be associated with less aggressive behaviour in early stage cervical carcinoma. The transition to bcl-2 independence may play an important role in tumour progression.

Serum basic fibroblast growth factor and vascular endothelial growth factor and tumour growth kinetics in advanced colorectal cancer.

BACKGROUND: The development of new microvessels in the surrounding stroma is a prerequisite for tumour progression. Basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) are angiogenic factors expressed in a broad range of human tumours. We have measured the concentrations of both cytokines in the serum of patients with advanced colorectal cancer. We questioned whether these levels are related to the number of tumour sites, the volume of liver and/or lung involvement and the growth kinetics. PATIENTS AND METHODS: 44 untreated colorectal adenocarcinoma patients who had developed metastatic and/or recurrent disease were evaluated. Serum levels of bFGF and VEGF were repeatedly measured using ELISA. The extent of target organ involvement and the kinetics of tumour volume growth were determined on consecutive computer tomography (CT) images. RESULTS: Patients with a tumour volume doubling time of less than 6 months showed a higher bFGF and VEGF serum level than others, independent of the number of sites involved and the extent of the metastatic disease. CONCLUSIONS: The data suggest a predictive value of serum bFGF and VEGF levels for the progression of disease in patients with untreated metastatic colorectal cancer. The results corroborate the importance of angiogenesis in the process of tumour growth. The serum levels might prove a useful tool in the quantification of angiogenesis and might be of valuable information in the decision process of initiating palliative chemotherapy. It will be of considerable importance to investigate whether the serum bFGF and VEGF levels have a predictive value on the probability of response to cytotoxic therapy.

Correlation of the response to cisplatin of human ovarian cancer cell lines, originating from one tumor but with different sensitivity, with the recovery of DNA adducts.

Cis-Diamminedichloroplatinum(II) (CDDP) is used in the treatment of various cancers, with or without ionizing radiation. During treatment, resistance may develop, and cross-resistance can also occur. DNA is the main target for CDDP and ionizing radiation, and we therefore evaluated the correlation between the amount of CDDP-DNA adducts and the cytotoxic activity of CDDP in human ovarian cancer cell lines with different platinum sensitivities. DNA-adduct levels were investigated 18 hr after CDDP exposure in three cell lines originating from the same human ovarian cancer. The least sensitive cells appeared to have the largest amounts of CDDP-DNA adducts, while the most sensitive had higher adduct levels than the parental cells. The proportion of the four adducts measured (i.e., Pt-G, Pt-AG, Pt-GG, and G-Pt-G) was comparable in all cell lines, with a preference for Pt-GG adduct formation (> 50% of the adducts). Intracellular CDDP concentrations were higher in sensitive than in resistant cells, in contrast to the degree of CDDP adduct formation. Data obtained following continuous exposure of CDDP-resistant cells to CDDP suggest that DNA repair is partly responsible for resistance to CDDP. We conclude that the amount of CDDP-DNA adduct formation in cancer cells is not a predictor of CDDP cytotoxicity.

[In vitro effects of piracetam on the radiosensitivity of hypoxic cells (adaptation of MTT assay to hypoxic conditions)]. / Effets in vitro du piracetam sur la radiosensibilité des cellules hypoxiques (adaptation du test au MTT aux conditions d'hypoxie).

This paper describes the adaptation of the MTT assay to hypoxic conditions in order to test the in vitro effect of piracetam on hypoxic cells and particularly on the radiosensitivity of hypoxic cells since this drug has shown clinical effect on acute and chronic hypoxia. The V79 cell line was selected by reference to preliminary hypoxic experiments using clonogenic assay and euoxic experiments using clonogenic and MTT assays. Cell growth and survival in our hypoxic conditions were assessed using MTT assay with an enclosure and special 48-well plates both made of glass. Growth curves on glass versus reference polystyrene plates were comparable and confirm the validity of using special glass plates. Growth curves on glass plates after 1-hour exposure to nitrogen versus air were comparable, so there is no bias effect due to gas composition. Survival curves using MTT versus reference clonogenic assay were comparable after radiation exposure in eu- and hypoxic conditions, and confirm the validity of our original technique for creating hypoxia. The Oxygen Enhancement Ratio was of about 3 for 1-hour hypoxic exposure. Piracetam gave no cytotoxic effect up to 10 mM of piracetam. Growth curves after continuous drug exposure and 1-hour euoxic versus hypoxic exposure gave no cytotoxic effect up to 10 mM of piracetam. Survival curves after continuous drug exposure to 10 mM of piracetam gave no significant effect on the radiosensitivity of hypoxic V79 cells using MTT or clonogenic assay. However, this does not preclude a potential in vivo effect of piracetam on the radiosensitivity owing to its action on microcirculation and its rheologic properties. The adaptation of the MTT assay to hypoxic irradiation conditions yields the easy screening of radiosensitizing drugs: shorter incubation, semi-automatic method and simultaneous analysis with different serial concentrations thanks to the special 48-well glass plates.

Resistance patterns between cis-diamminedichloroplatinum(II) and ionizing radiation.

Cross-resistance between cis-diamminedichloroplatinum(II) (CDDP) and radiation resistance has been suggested from clinical and experimental data (C. T. Coughlin and R. C. Richmond, Semin. Oncol., 16: 31-43, 1989). To determine whether cross-resistance patterns between both cytotoxic approaches exist, resistance against CDDP and ionizing radiation was induced separately in human ovarian cancer cells in a cross-over design. Subsequently sensitivity changes were determined for both treatment modalities. CDDP resistance was induced previously (P. J. Kuppen et al., Cancer Res., 48: 3355-3359, 1988), and resistant cells were grown at three different levels of CDDP:0 ng/ml; 250 ng/ml; and 500 ng/ml. Resistance with resistance factor (RF) 3.4 to 5.1 proved to be stable, since withdrawal of CDDP pressure for at least 6 mo did not alter resistance patterns. CDDP-resistant cells also demonstrated stable resistance against ionizing radiation, with RF ranging from 1.7 to 2.0. The resistance patterns could not be explained by differences in growth kinetics and DNA content. Resistance to ionizing radiation was induced in the same human ovarian cancer cells as used for CDDP resistance studies. Exposure with 1.5 Gy of intermittent irradiation during 6 mo, at time intervals of 48 h, resulted in cells which were able to grow under chronic ionizing radiation pressure. RF was 2.0; the resistance was lost after 6 mo of culturing without ionizing radiation pressure. With intermittent radiation doses of 0.5 and 1.0 Gy, no significant resistance could be induced. Cells intermittently exposed to 0.5, 1.0, and 1.5 Gy during 6 mo demonstrated increased sensitivity to CDDP, with 0.22 less than RF less than 0.43. Increased sensitivity was associated with proportionally increased formation of the platinum-DNA adducts. Differences in sensitivity for both ionizing radiation and CDDP were lost after 6 mo of culturing without radiation pressure; therefore, resistance toward ionizing radiation and, likewise, the increased sensitivity to CDDP, were judged to be unstable. In conclusion, data of the present study demonstrated that development of stable resistance to CDDP is associated with development of stable resistance to ionizing radiation in human ovarian cancer. Contrastingly, increased sensitivity to CDDP was found when resistance against irradiation was induced in the same cells.