In vitro short-term chemosensitivity test in head and neck tumors

A new method to test the sensitivity of human tumor cells has been developed. A suspension of mechanically dissociated tumor cells is kept in continuous incubation for 24h, in cultures with antineoplastic agents. Drug induced cell cycle perturbations are monitored by flow cytometric computer analysis and DNA distributions of the cells stained with propidium iodide are expressed in percentage. The test is used in 15 head and neck human solid tumors. The drugs tested were: VCR, EpiDx, CDDP, MTX, 5-FU, CPM, BLM. The results obtained reveal that tumor sensitivity varies independently from the stage and malignity grading. Therapeutic combinations are assigned by selecting the drugs on the basis of the individual in vitro response.     

Effect of histone deacetylase inhibitor LAQ824 on antineoplastic action of 5-Aza-2′-deoxycytidine (decitabine) on human breast carcinoma cells

Purpose: Epigenetic silencing of tumor suppressor genes (TSGs) by aberrant DNA methylation and chromatin deacetylation provides interesting targets for chemotherapeutic intervention by inhibitors of these events. 5-Aza-2′-deoxycytidine (decitabine, 5AZA-CdR) is a potent demethylating agent, which can reactivate TSGs silenced by aberrant DNA methylation. LAQ824 (LAQ) is a novel inhibitor of histone deacetylase (HDAC) that shows antineoplastic activity and can activate genes that produce cell cycle arrest. Both 5AZA-CdR and LAQ as single agents are currently under clinical investigation in patients with cancer. Previous reports indicate that the “cross-talk” between inhibitors of DNA methylation and HDAC can result in a synergistic activation of silent TSGs. These observations suggest that combination of these inhibitors may be an effective form of epigenetic therapy for breast cancer. The objective of our study was to determine if the combination of 5AZA-CdR and LAQ would show additive or synergistic antineoplastic activity on human MDA-MB-231 and MCF-7 breast carcinoma cells. The antineoplastic activity of these agents was evaluated by clonogenic assay and inhibition of DNA synthesis. Results: The combination produced greater antineoplastic activity for the MDA-MB-231 tumor cells than either agent alone. For the MCF-7 tumor cells, there were signs of antagonism between 5AZA-CdR and LAQ when administered simultaneously. When a sequential schedule (first 5AZA-CdR followed by LAQ) was used, there were no signs of antagonism of the antineoplastic action for the MCF-7 tumor cells. The mechanism of this interaction is probably due to the reduction of progression of MCF-7 tumor cells into S phase by LAQ. This would interfere with the antineoplastic action of 5AZA-CdR, since it is an S phase specific agent. Conclusions: These studies demonstrated the importance of the schedule of administration of 5AZA-CdR and LAQ and may have application for future clinical trials on the treatment of breast cancer with these agents.     

Current management of glioblastoma multiforme

Glioblastoma multiforme is the most common primary brain tumor in adults. Despite major research efforts and progress in neuroimaging, neurosurgery, and radiation and medical oncology, the overall survival of patients with this disease has changed little over the past 30 years. Surgery and radiation therapy remain critical components in the care of patients with glioblastoma multiforme. Treatment with chemotherapy has been hampered by the apparent resistance of these tumor cells to available agents and challenges in delivering agents to the tumor cells. The blood-brain barrier can restrict entry of some agents and the effect of antiepileptic drugs inducing hepatic P450 can significantly affect the pharmacology of a wide range of antineoplastic agents. As a result, new agents and novel approaches are required. Translational research efforts should: (1) pursue a broad research agenda until productive avenues are identified; (2) quantify the delivery of novel agents to the malignant brain tumor cells; (3) determine the maximum tolerated dose (MTD) and preliminary efficacy data on novel agents before initiating combination therapies; (4) optimize trial designs; and (5) improve psychosocial and supportive care for patients with this devastating illness.     

MTT法应用于肝癌化学免疫治疗敏感性研究

目的 探讨MTT法应用于肝癌细胞化疗敏感性检测及化疗与免疫治疗的合理应用。方法 应用MTT法检测肝癌细胞的化疗敏感性和化疗对肿瘤浸润淋巴细胞（TIL）的毒性。结果 肝癌细胞和TIL细胞数增多与生成的甲Xun（formazan)的光密度（OD）值呈线性正相关。TIL在体外对自体肝癌细胞显示高活性的细胞毒作用。肝癌细胞对化疗药物的敏感性存在较大的个体差异。化疗药物对TIL的毒性作用大于对肝癌细胞的杀伤作用。结论 以MTT法作肝癌细胞化疗敏感性检测,既可指导临床选用肿瘤敏感性化疗药物,又可避免盲目选用肿瘤非敏感性化疗药物对机体抗肿瘤免疫的毒性;TIL过继免疫治疗与化疗不宜同时应用。     

Different effect of paclitaxel on primary tumor mass, tumor cell contents, and metastases for four experimental human prostate tumors expressing luciferase.

PURPOSE: Primary tumor growth is usually assessed by measuring tumor mass or volume, under the assumption that such variables correlate with the contents of tumor cells. However, tumors are complex interacting mixtures of tumor cells and host components. The different sensitivity of such components to cytostatic agents should be taken into consideration when evaluating the effectiveness of antineoplastic agents. We evaluate the effect of the antineoplastic agent paclitaxel on primary tumors expressing luciferase and their metastases using a sensitive luminescence-based procedure to directly asses the number tumor cells, in comparison with traditionally used tumor mass measurement. EXPERIMENTAL DESIGN: Nude mice bearing human prostate tumors expressing the luciferase gene, LNCaP.Sluc, DU 145.Sluc, and PC-3.Sluc, i.m. inoculated, and PC-3M.Sluc, orthotopically inoculated, were subjected to a 10-day treatment with either 10 mg/kg/d paclitaxel or saline solution. At the end of the treatment period, primary tumors as well as metastasis target organs were harvested, weighed, and homogenized. The presence of tumor cells in the tissue homogenates was evaluated using a luminometer, following the addition of luciferin. Tumor cell equivalent is defined as the amount of light produced by a single tumor cell in culture. RESULTS: Paclitaxel had a different effect on the primary tumor mass and the contents of tumor cells for each tumor type. Whereas LNCaP.Sluc, PC-3.Sluc, and PC-3M.Sluc primary tumor masses were significantly reduced by the action of paclitaxel, their contents in tumor cell equivalents were not significantly affected. In contrast, paclitaxel only reduced significantly the number of tumor cell equivalents in DU 145 primary tumors. In the lymph nodes, paclitaxel reduced the number of DU 145.Sluc metastases significantly, by a factor of 10(3), but had no significant effect on the rest of tumor cells. However, in lungs and muscle, paclitaxel treatment reduced significantly the number of metastatic PC-3.Sluc and PC-3M.Sluc tumor cell equivalents. In the bones, no tumor cell type was significantly affected by paclitaxel. CONCLUSIONS: Some components of tumor stroma seem to be more sensitive to antineoplastic agents than the tumor cells themselves and may also contribute to modulate the response to therapy. Our results caution against the use of a single general variable, such as tumor mass, to evaluate the effectiveness of antineoplastic agents and emphasize the effect of the tumor cell environment in their sensitivity to treatment.     

Regional treatment strategies for in-transit melanoma metastasis

For in-transit melanoma confined to the extremities, regional chemotherapy in the form of hyperthermic isolated limb perfusion and isolated limb infusion are effective treatment modalities carrying superior response rates to current standard systemic therapy. Despite high response rates, most patients will eventually recur, supporting the role for novel research aimed at improving durable responses and minimizing toxicity. Although the standard cytotoxic agent for regional chemotherapy is melphalan, alternative agents such as temozolomide are currently being tested, with promising preliminary results. Current strategies for improving chemosensitivity to regional chemotherapy are aimed at overcoming classic resistance mechanisms such as drug metabolism and DNA repair, increasing drug delivery, inhibiting tumor-specific angiogenesis, and decreasing the apoptotic threshold of melanoma cells. Concurrent with development and testing of these agents, genomic profiling and biomolecular analysis of acquired tumor tissue may define patterns of tumor resistance and sensitivity from which personalized treatment may be tailored to optimize efficacy. In this article rational strategies for treatment of in-transit melanoma are outlined, with special emphasis on current translational and clinical research efforts.     

Antineoplastic effects and mechanism of action of IFN-alpha on brain tumors with use of fluorescent isothiocyanate-labelled IFN

The antineoplastic effects and mechanism of IFN-alpha with a newly designed fluorescent isothiocyanate-labelled IFN-alpha were studied on three established glioma-cell lines and cultured cells of clinical brain tumors. Viability, cell cycle and cells showing positive reaction with fluorescent isothiocyanate-labelled IFN were analyzed by flow cytometry. U373MG glioma cells in contact with 10(4) IU/ml of IFN for 24 hours had a dose dependency, decreased viability, S-phase block in the cell cycle and high rate of positive reaction with fluorescent isothiocyanate-labelled IFN. Two surgical cases, except for one case, showed similar results and other cell lines or meningiomas were not affected by IFN. As the antineoplastic effects of IFN-alpha correlated with the rate of occurrence of positive cells with fluorescent isothiocyanate-labelled IFN, sensitive tumor cells may have a respective specific receptor for IFN-alpha, and, therefore, fluorescent isothiocyanate-labelled IFN-alpha might be of clinical value with regard to the problem of the receptor as well as sensitivity test.     

Probenecid is a chemosensitizer in cancer cell lines

Resistance and toxicity are the major barriers to successful cancer chemotherapies. Developing molecules that reduce drug resistance and improve antineoplastic effects is of great interest for cancer research; ideally, these substances should not affect the pharmacodynamics of the chemotherapeutic agent while providing a synergistic antineoplastic effect. In this study, we tested in vitro co-administration of the antineoplastic agents cisplatin or paclitaxel with probenecid, an anion channel inhibitor, in a panel of cancer cell lines to determine the cytotoxicity and synergistic effects of these drug combinations. In addition, we measured the clonogenicity and apoptotic index in these cells. We observed a synergistic interaction between probenecid and the chemotherapeutic agents, and increasing doses of probenecid resulted in a significant decrease in the effective doses of the chemotherapeutic agents. For the antineoplastic agent and probenecid combinations, we found increased cell death, reduced colony formation, and a higher number of apoptotic cells, compared with treatment of cisplatin or paclitaxel alone. Further research is necessary to elucidate the molecular mechanisms by which the synergistic effect occurs. If these synergistic effects can be reproduced in vivo, the co-administration of probenecid with different chemotherapeutic agents may provide a valid treatment in patients with chemotherapy resistance.     

Parameters affecting the ex vivo cytotoxic drug sensitivity of human hematopoietic cells

The drug sensitivity of normal cells provides a baseline for determining the therapeutic index, and therefore the effectiveness, of cytotoxic drugs, yet little is known about the factors that affect normal cell chemosensitivity. Some parameters are known to have a profound effect on tumor cell sensitivity. The purpose of this study was to determine how cytotoxic drug sensitivity of hematopoietic cells isolated from cancer patients was affected by various parameters. These included previous chemotherapy (yes or no), sex, age, tumor type (leukemias or solid tumors), sample source (blood, bone marrow, serous effusions, or tumor biopsies) and predominant cell lineage (lymphoid, myeloid, macrophage, or mixed). Mononuclear cells isolated from blood, bone marrow, serous effusions, and tumor biopsies were incubated for four days with a median of 16 drugs. The differential staining cytotoxicity assay, an ex vivo apoptotic drug sensitivity test in which cell survival is determined morphologically, was used to assess normal hematopoietic and tumor cell response to cytotoxic drugs. One hundred forty-six specimens yielded hematopoietic cell chemosensitivity results with 3-36 drugs. Compared with tumor cells, there was far less interpatient variation in chemosensitivity of hematopoietic cells. Mean hematopoietic cell drug sensitivity showed little variation due to previous chemotherapy, sex, age, tumor type, and sample source or cell lineage. We therefore concluded that cytotoxic drug sensitivity of hematopoietic cells from a variety of sources could be used for assessment of therapeutic index. Drug therapeutic index results are a valuable tool in identifying novel cytotoxic agents and individually tailored chemotherapy regimens.     

A radiometric method for evaluation of chemotherapy sensitivity: results of screening a panel of human breast cancer cell lines

We have used a radiometric method to screen for chemotherapy sensitivity among a panel of human breast cancer cell lines. This method utilizes the inhibition of conversion of [14C]glucose to 14CO2 as an index of cytotoxicity. Nine different breast cancer cell lines were exposed for 1 h to 4 different concentrations of several antineoplastic agents with and without documented clinical activity against breast cancer. Cytotoxic effects were analyzed as a function of the ratio of the concentration required to inhibit cell growth to 50% of control to 1/10 of the known peak plasma concentration in humans for each particular drug. The drug-induced inhibition of 14C production by breast cancer tumor cells correlated strongly with the drug-induced antiproliferative effect (P less than 0.002) and with the inhibition of colony formation in a soft agar cloning assay (P less than 0.05). The HS578T cell line and one of the MCF7 cell lines exhibited a chemosensitivity pattern consistent with the clinical responsiveness of human breast cancer to the agents tested. Most of the other cell lines exhibited resistance to clinically active agents, especially the cell lines obtained from patients exposed to prior chemotherapy. These results suggest that this radiometric method measures a drug-induced metabolic effect that correlates with the antiproliferative activity of antineoplastic agents on breast cancer cells. The HS578T and the MCF7-KO cell lines, tested in this system, could be a useful screen for new anticancer compounds with activity against human breast cancer.     

细胞周期检测点的流式细胞术分析

背景与目的:真核细胞的细胞周期运行遵循着严格的时相次序,这种精密的延缓和强制的次序,由细胞监控机制——检测点来完成,检测点功能的丧失会导致肿瘤的发生。传统的细胞周期检测点分析多数基于群体细胞DNA直方图的流式细胞术。本研究以晚G1期检测点为模式,建立一种新的细胞周期检测点分析方法——Cyclins/DNA双参数流式细胞术,并评价应用该方法进行细胞周期检测点分析的可行性和优越性。方法:将紫外线照射诱导后的人类急性淋巴细胞型白血病细胞株(MOLT-4)于不同时间点收获固定,分两组进行流式细胞仪检测:一组用DNA直方图法,Modifit软件分析计算G0/G1期细胞总数;另一组应用CyclinE/DNA双参数流式细胞术对G1晚期细胞CyclinE的荧光强度、阈值及G0/G1各亚期细胞数量进行定量分析,并比较两组实验结果。结果:用DNA直方图法观察到紫外线照射后0～4hG0/G1期细胞总数基本不变(5300～5500),6h后开始上升(6241,12.6%)。而用CyclinE/DNA双参数法观察到:(1)G1晚期细胞的CyclinE荧光强度于照射后短时间内便开始变化,1h上升为341.2(对照295.1,15.6%),6h上升为577.6(95.7%),此时CyclinE阈值上升到5.4(0h为2.0);(2)G0/G1各亚期细胞数目变化趋势不明显:G1晚期细胞数6h时略为减少(此时凋亡率为5.61%),G1早期细胞数缓慢上升。结论:CyclinE/DNA双参数流式细胞术将CyclinE的荧光强度及表达阈值定量化,对于细胞晚G1期检测点的检测比传统的DNA直方图法更为敏感和精确。     

Gestational trophoblastic neoplasia

Gestational trophoblastic neoplasia (GTN) is one of the most curable malignancies because of the intrinsic sensitivity of the tumor to certain antineoplastic agents, effective sensitive assays for human chorionic gonadotropin (hCG), and identification of high‐risk factors that permit individualized treatment. Chemotherapy is the main modality of treatment in patients with GTN. The cure rate in patients with low‐risk GTN is 100%, and is estimated to exceed 80% in patients with high‐risk GTN. Management of GTN is based on staging (anatomical involvement staging) and scoring. Patients with persistent GTN and stage I or score ≤ 6 (low risk) should be managed with single agent chemotherapy (methotraxate or actinomycin), but patients with stage IV or score ≥ 7 (high risk) need combination chemotherapy. Gestational trophoblastic neoplasia is radiosensitive, because radiation has hemostatic and tumorocidal effect on GTN. Therefore, radiotherapy can be used in treatment of some patients with brain hepatic metastasis or in patients where chemotherapy is not possible due to medical problems. Surgery can be used in patients who are resistant to chemotherapy or in hemorrhagic cases. Surgical resection of the tumor is the main form of therapy for placental site trophoblastic tumor. This surgery consists of a hysterectomy for the majority of patients as the disease is confined to the uterus.     

Use of proteasome inhibition in the treatment of lung cancer

The proteasome plays a critical role in the degradation of proteins involved in the regulation of cell cycle, apoptosis, and angiogenesis. Bortezomib is the first in a new class of antineoplastic agents known as proteasome inhibitors to become available for clinical use. Bortezomib targets pathways relevant to tumor progression and therapy resistance and can directly modulate expression of cyclins, p27kip1, p53, nuclear factor-kB, Bcl-2, and Bax. In in vitro and in vivo, growth inhibition and apoptosis have been observed in tumor cells following exposure to bortezomib. Currently, bortezomib is approved for the treatment of patients with relapsed and/or refractory multiple myeloma who have received > or =2 therapies and progressed on their most recent therapy. Efforts are now being directed toward exploring the use of bortezomib in the treatment of advanced non-small-cell lung cancer (NSCLC). Clinical trials using bortezomib as monotherapy or in combinations, such as with taxanes, gemcitabine and platinums, and novel agents are under way, and preliminary results have demonstrated activity with bortezomib as a single agent and in combination with chemotherapy in advanced NSCLC. In addition, pharmacogenomics and biomarker analysis are being used in an attempt to identify tumor types likely to respond to treatment with bortezomib.     

Check samples for laboratory self-assessment in DNA flow cytometry. The National Cancer Institute's Flow Cytometry Network experience

The National Cancer Institute's Flow Cytometry Network (NCI-FCN) is attempting to facilitate the transfer of flow cytometry (FCM) of exfoliated bladder cells from the research laboratory to the clinical laboratory. Demonstrating interinstitutional consistency in FCM analysis of replicate specimens simulating clinical barbotage specimens, fixed to allow easy transportation and storage at room temperature was one specific objective. Simulated barbotage specimens were prepared by mixing cultured aneuploid bladder carcinoma cells with normal or mitogen-stimulated peripheral blood mononuclear cells in different ratios. The samples were fixed in 10% formalin for 30 minutes, stored in buffer, and enucleated with pepsin, pH 1.5, before staining with propidium iodide for FCM DNA analysis. Preservation in ethanol or other common DNA cytochemical reagents was found to be unsatisfactory. In contrast, the formalin-fixed samples showed excellent preservation of quantitative DNA fluorescence and coefficient of variation of histogram peaks for over 2 weeks. Exchange of eight fixed specimens among five network laboratories that analyzed them as "unknowns" showed good overall agreement on histogram data and interpretation, although some noteworthy interlaboratory differences were found. This technique could be used for self-assessment surveys of clinical laboratory performance in DNA FCM of bladder barbotage specimens.     

姜黄素诱导人膀胱癌UMUC2细胞株凋亡的作用

目的为寻找有效无毒的膀胱灌注药物用于膀胱肿瘤术后预防肿瘤种植与复发,我们观察了姜黄素对人膀胱癌细胞UMUC2的细胞毒效应及诱导凋亡的体外作用。方法以0~160 μmol/L姜黄素作用于UMUC2细胞1~48 h,应用MTT法、平板克隆实验观察姜黄素的细胞毒效应,荧光染色观察凋亡形态学改变,流式细胞仪进行细胞周期分析及凋亡定量测定,免疫细胞化学染色观察凋亡相关蛋白p53和Survivin的表达。结果所有浓度组姜黄素均对膀胱癌UMUC2细胞有明显的生长抑制作用,160 μmol/L姜黄素作用1 h对全部癌细胞是致命的。荧光染色观察到典型的核凝集、碎裂凋亡形态学改变。流式细胞术定量分析了亚G1峰,后者同时表明姜黄素导致的细胞周期阻滞以G2/M期为主,使S期细胞比例显著减少。免疫细胞化学染色显示姜黄素下调p53、Survivin蛋白的表达。结论姜黄素明显抑制膀胱癌细胞系UMUC2的生长并诱导凋亡,导致细胞G2/M期阻滞,其作用机制与其下调p53、Survivin的表达相关,克隆形成实验证实大剂量姜黄素、短期作用对膀胱癌细胞系UMUC2有致命的细胞毒效应,显示了姜黄素用于膀胱癌患者的化学治疗,尤其是腔内灌注化疗的可能性。     

Differential toxicities of anticancer agents among DNA repair and checkpoint mutants of Saccharomyces cerevisiae

Most cytotoxic anticancer agents damage DNA directly, interfere with DNA metabolism or chromosome segregation, and are particularly toxic in dividing cells. Although a considerable amount of information on the mechanisms of action of these agents is available, the molecular bases for selective tumor cell killing by chemotherapy are largely unknown. Many genetic alterations found in sporadic and hereditary cancers affect functions in DNA repair and cell cycle control and result in sensitivity to DNA damaging agents. We have therefore set out to determine the effects of these cancer mutations on sensitivity or resistance to various chemotherapeutic agents. Because most of the affected genes are well conserved among eukaryotes, we have carried out a comprehensive analysis of a panel of isogenic yeast strains, each defective in a particular DNA repair or cell cycle checkpoint function, for sensitivity to the Food and Drug Administration-approved cytotoxic anticancer agents. Widely different toxicity profiles were observed for 23 agents and X-rays, indicating that the type of DNA repair and cell cycle checkpoint mutations in individual tumors could strongly influence the outcome of a particular chemotherapeutic regimen.     

Promising survival for patients with glioblastoma multiforme treated with individualised chemotherapy based on in vitro drug sensitivity testing

We retrospectively investigated the efficacy and feasibility of individualised chemotherapy based on in vitro drug sensitivity testing (DST) for patients with glioblastoma multiforme. A total of 40 consecutive patients with glioblastoma multiforme (GM) were enrolled into this study between January 1995 and December 2000. The flow cytometric (FCM) detection of apoptosis was used to determine the in vitro sensitivity of tumour cells obtained at surgery to 30 different kinds of anticancer agents. From the results of FCM assay, an in vitro best regimen was prospectively selected. All the patients concurrently received the individualised chemotherapy with the in vitro best regimen and 60 Gy of conventional radiation therapy. Of the 31 assessable patients, eight patients (26%) achieved partial response, and 20 patients (65%) had stable disease. The median survival time was 20.5 months. The individualised chemotherapy based on in vitro DST was associated with favourable survival time for the patients with GM compared with the reported results of conventional therapy regimens. The present result suggests that the currently available anticancer agents could be effective against GM when used in individualised chemotherapy.     

Structure-activity relationships of alkylphosphocholine derivatives: antineoplastic action on brain tumor cell lines in vitro

Erucylphosphocholine (ErPC) is a promising candidate for the treatment of human brain tumors. The aim of the present study was to investigate whether structural modifications of ErPC would improve its antineoplastic activity in vitro. The novel alkylphosphocholine (APC) derivatives docosenyl-( cis-10,11)-phosphocholine, tricosenyl-( cis-12,13)-phosphocholine, heneicosenyl-( cis-12,13)-phosphocholine and erucyl- N, N, N-trimethylpropanolaminophosphate all reduced cell growth and viability of rat and human astrocytoma/glioblastoma (AC/GBM) cell lines (C6, T98G, U87MG, A172) and had improved antineoplastic activity when compared to the prototypical APC hexadecylphosphocholine (HePC). However, the four cell lines differed in their sensitivity to the APC derivatives. A172 cells were most sensitive to their cytostatic action and T98G cells to their cytotoxic action. The LC(50) values for T98G cells after a 72-h exposure to the novel derivatives varied between 25 and 54 microM compared to 45+/-8.1 microM for ErPC. Complete killing of T98G cells was obtained with all derivatives at 90 microM. Structural modifications of the chain length of the alcohol moiety as well as changing the position of the double bond within the alkyl chain improved cytotoxicity of the APC in C6 and A172 cells and to a lesser extent in T98G cells, whereas U87MG cells showed almost similar sensitivities to the novel drugs and ErPC. Increasing the distance between the phosphorus and nitrogen atoms within the polar phosphocholine group did not alter antineoplastic activity but modified physicochemical characteristics, e.g. increased the solubility in water. In a similar manner to ErPC, all derivatives induced growth arrest in the G(2)/M phase of the cell cycle and apoptotic cell death. Importantly, none of the derivatives showed hemolytic activity. As there was no clear superiority of any of the novel derivatives, ErPC remains the leading APC derivative for future clinical trials in brain tumor chemotherapy.     

Combination chemotherapy with aclarubicin and cisplatinum against malignant intracranial tumor--an in vitro study

Augmentation of cytotoxicity against cultured human tumor cell lines (5 gliomas, 2 neuroblastomas, 2 sarcomas) using a combination of Aclarubicin (ACR) and Cisplatinum (CDDP) was analysed in vitro from the viewpoints of cell growth inhibition and alteration of the DNA histogram. Synergistic effects of the combination of the two agents were observed in 7 of the 9 cell lines. In sarcoma cell lines, effects were demonstrated even by a low dose of 0.1 microgram/ml CDDP and 0.01 microgram/ml ACR. Flow cytometry studies of the DNA histogram showed increase of accumulation in the S phase following the G2-M phase and reduction of G1 phase cells in response to the combination. From the present experimental studies in vitro, it is concluded that combination chemotherapy with ACR and CDDP may be effective for sarcoma and ACNU-resistant glioma. The mechanism of the synergistic effect produced by the combination is suggested to be impairment of RNA synthesis by ACR which prevents the repair of DNA damage induced by CDDP.     

Drug distribution in tumors: Mechanisms,role in drug resistance,and methods for modification

Distribution of antineoplastic agents within tumors remains one of the major challenges in cancer chemotherapy because distribution is hampered by several factors related to the drug (its physicochemical characteristics) and to the neoplastic tissue (blood and lymphatic vasculature, cell density, extracellular matrix composition, and interstitium). The inhomogeneous distribution and structure of tumor vasculature lead to large avascular and hypoxic areas with low pH and high interstitial oncotic pressure. In these critical conditions, the gradient of drug concentrations from the vessels to the inner parts of the tumor is not sufficient to promote diffusion of pharmacologic agents. Again, cellular sequestration and binding to extracellular matrix represent further factors that limit drug distribution and reduce tumor sensitivity to chemotherapy. Several strategies have been investigated to circumvent drug resistance. The evaluation of liposomal and nanoparticle formulations and the characterization of newer bioreductive agents and drugs that should normalize tumor vasculature are in progress.