Adenovirus-mediated p53 gene therapy has greater efficacy when combined with chemotherapy against human head and neck, ovarian, prostate, and breast cancer

Purpose: Adenovirus-mediated p53 gene therapy for cancer is currently undergoing phase I/II clinical trials. The drug used in our clinical trials (p53 Ad; ACN53; SCH58500) consists of a replication-deficient, type 5 adenovirus vector expressing human wildtype p53 tumor suppressor under the control of the cytomegalovirus promoter. In preclinical models, p53 Ad has therapeutic efficacy against a wide range of human tumor types containing nonfunctional p53, both in vitro and in vivo. Results from early clinical trials using p53 gene therapy by itself support optimism for the future of this therapeutic approach. However, it is likely that many phase II/III trials will incorporate an arm comparing traditional chemotherapy against chemotherapy combined with p53 gene therapy. Therefore, it is important to study possible interactions between p53 Ad and chemotherapeutic drugs in preclinical models before starting the clinical trials. Methods: Proliferation of tumor cells was quantitated after incubation with various combinations of p53 Ad and chemotherapeutic drugs. Human tumor xenografts in scid mice were dosed with intraperitoneal or intratumoral p53 Ad with or without chemotherapeutic drugs and the tumor burden after therapy monitored. Results: p53 Ad combined with cisplatin, doxorubicin, 5-fluorouracil, methotrexate, or etoposide inhibited cell proliferation more effectively than chemotherapy alone in SCC-9 head and neck, SCC-15 head and neck, SCC-25 head and neck, SK-OV-3 ovarian, DU-145 prostate, MDA-MB-468 breast, and MDA-MB-231 breast tumor cells. No obvious dependence on dosing schedule was observed. Greater anticancer efficacy was also demonstrated in four human tumor xenograft models in vivo. Of particular significance, there was enhanced efficacy using the three drug combination of p53 Ad, cisplatin, and paclitaxel in an ovarian cancer model. Conclusion: These results support the combination of p53 gene therapy with chemotherapy in clinical trials. Received: 5 October 1998 / Accepted: 3 December 1998     

Assessment of p53 gene transfer and biological activities in a clinical study of adenovirus-p53 gene therapy for recurrent ovarian cancer

A cohort study was designed to evaluate the efficiency of gene transfer and whether biological activity from the expressed therapeutic gene resulted after administration of a recombinant adenovirus containing the human wild-type p53 (p53(wt)) gene (rAd-p53 SCH 58500). The cohort study was conducted in five trial subjects with recurrent ovarian cancer. Each trial subject received multiple cycles of rAd-p53 SCH 58500, each cycle comprised of doses of 7.5 x 10(13) particles on each of five consecutive days. Subjects were treated with rAd-p53 SCH 58500 alone during Cycle 1 and in combination with gemcitabine during the subsequent cycles. Both tumor biopsies and peritoneal aspirates were collected and evaluated for gene transfer and evidence of the biological activities of the expressed p53(wt) gene. Using quantitative PCR and RT-PCR, and in situ PCR, gene transfer and expression were documented in tumor biopsies (four of five patients) collected from Cycle 1. Furthermore, upregulation of p21/WAF1, bax and mdm-2, and downregulation of survivin were observed in these same tumor biopsy samples, suggesting that intraperitoneal administration of rAd-p53 SCH 58500 leads to detectable p53 biological activity in target tumor tissue. In addition, gene transfer and its expression were observed in cells obtained from peritoneal aspirates. These fluids were mainly comprised of polymorphonuclear neutrophils, indicating that successful gene transfer can be achieved by multiple cycle intraperitoneal administration of recombinant adenovirus.     

Combination therapy with the farnesyl protein transferase inhibitor SCH66336 and SCH58500 (p53 adenovirus) in preclinical cancer models

SCH66336 is a p.o.-active, farnesyl protein transferase inhibitor. SCH66336 inhibits farnesylation of RAS and other proteins in tumor cells and suppresses tumor growth in human xenograft and transgenic mouse cancer models in vivo. SCH58500 is a replication-deficient, recombinant adenovirus, which expresses the human p53 tumor suppressor. In preclinical models, SCH58500 has therapeutic efficacy against a wide range of human tumor types containing nonfunctional p53 and enhanced activity in combination with many chemotherapeutic drugs. Here we report that combination therapy with SCH66336 and SCH58500 has synergistic or additive antiproliferative effects on a panel of tumor cells lines in vitro. The efficacy of the three-drug combination of SCH66336, SCH58500, and paclitaxel was also examined in vitro. Each two-drug interaction displayed such marked synergy, the addition of a third drug to the statistical model could only yield additivity. Greater combined efficacy for SCH66336 and SCH58500 was also observed in vivo in the DU-145 human prostate and wap-ras/F transgenic mouse cancer models.     

Combination therapy with SCH58500 (p53 adenovirus) and cyclophosphamide in preclinical cancer models

SCH58500 (ACN53) is a replication-deficient, recombinant adenovirus which expresses human p53 tumor suppressor. In preclinical models, SCH58500 has therapeutic efficacy against a wide range of human tumor types containing nonfunctional p53 and it has enhanced activity in combination with many chemotherapeutic drugs. However, the anti-tumor efficacy of SCH58500 combined with the DNA-damaging chemotherapeutic cyclophosphamide has not been previously reported. Cyclophosphamide did not enhance the activity of SCH58500 in three out of four human tumor xenograft models studied. Furthermore, combination therapy with SCH58500 and cyclophosphamide was not any better than single drug treatment in transgenic H-ras mice and in FVB mice bearing syngeneic MidT2-1 tumors. This is in sharp contrast to previous combination studies in these models where SCH58500 had enhanced efficacy when given with the farnesyl protein transferase inhibitor SCH66336, paclitaxel, cisplatin, cisplatin/paclitaxel, or doxorubicin. Further evaluation of this combination is required before it can be recommended for clinical trials in cancer patients.     

Biological activities of a recombinant adenovirus p53 (SCH 58500) administered by hepatic arterial infusion in a Phase 1 colorectal cancer trial

The major focus of intrahepatic arterial (IHA) administration of adenoviruses (Ad) has been on safety. Currently, there is little published data on the biological responses to Ad when administered via this route. As part of a Phase I study, we evaluated biological responses to a replication-defective adenovirus encoding the p53 transgene (SCH 58500) when administered by hepatic arterial infusion to patients with primarily colorectal cancer metastatic to the liver. In analyzing biological responses to the Ad vector, we found that both total and neutralizing Ad antibodies increased weeks after SCH 58500 infusion. The fold increase in antibody titers was not dependent on SCH 58500 dosage. The proinflammatory cytokine interleukin-6 (IL-6) transiently peaked within 6 h of dosing. The cytokine sTNF-R2 showed elevation by 24 h post-treatment, and fold increases were directly related to SCH 58500 doses. Cytokines TNF-alpha, IL-1beta, and sTNF-R1 showed no increased levels over 24 h. Predose antibody levels did not appear to predict transduction, nor did serum Ad neutralizing factor (SNF). Delivery of SCH 58500 to tumor tissue occurred, though we found distribution more predominantly in liver tissues, as opposed to tumors. RT-PCR showed significantly higher expression levels (P<0.0001, ANOVA) for adenovirus type 2 and 5 receptor (CAR) in liver tissues, suggesting a correlation with transduction. Evidence of tumor-specific apoptotic activity was provided by laser scanning cytometry, which determined a coincidence of elevated nuclear p53 protein expression with apoptosis in patient tissue. IHA administration of a replication defective adenovirus is a feasible mode of delivery, allowing for exogenous transfer of the p53 gene into target tissues, with evidence of functional p53. Limited and transient inflammatory responses to the drug occurred, but pre-existing immunity to Ad did not preclude SCH 58500 delivery.     

Successful adenovirus-mediated wild-type p53 gene transfer in patients with bladder cancer by intravesical vector instillation.

PURPOSE: To study safety, feasibility, and biologic activity of adenovirus-mediated p53 gene transfer in patients with bladder cancer. PATIENTS AND METHODS: Twelve patients with histologically confirmed bladder cancer scheduled for cystectomy were treated on day 1 with a single intratumoral injection of SCH 58500 (rAd/p53) at cystoscopy at one dose level (7.5 x 10(11) particles) or a single intravesical instillation of SCH 58500 with a transduction-enhancing agent (Big CHAP) at three dose levels (7.5 x 10(11) to 7.5 x 10(13) particles). Cystectomies were performed in 11 patients on day 3, and transgene expression, vector distribution, and biologic markers of transgene activity were assessed by molecular and immunohistochemical methods in tumors and normal bladder samples. RESULTS: Specific transgene expression was detected in tissues from seven of eight assessable patients treated with intravesical instillation of SCH 58500 but in none of three assessable patients treated with intratumoral injection of SCH 58500. Induction of RNA and protein expression of the p53 target gene p21/WAF1 was demonstrated in samples from patients treated with SCH 58500 instillation at higher dose levels. Distribution studies after intravesical instillation of SCH 58500 revealed both high transduction efficacy and vector penetration throughout the whole urothelium and into submucosal tumor cells. No dose-limiting toxicity was observed, and side effects were local and of transient nature. CONCLUSION: Intravesical instillation of SCH 58500 combined with a transduction-enhancing agent is safe, feasible, and biologically active in patients with bladder cancer. Studies to evaluate the clinical efficacy of this treatment in patients with localized high-risk bladder cancer are warranted.     

Ectopic expression of interferon regulatory factor-1 promotes human breast cancer cell death and results in reduced expression of survivin

The overexpression of the inhibitor of apoptosis protein, survivin, may provide tumor cells with a distinct survival advantage in situ; hence, therapeutic strategies have been designed to inhibit its expression. In this study, we ectopically expressed the interferon regulatory factor (IRF)-1 protein in the breast carcinoma cell lines MDA-MB-468 and SK-BR-3 using a recombinant adenovirus (Ad-IRF-1). By screening microarray analysis of cDNA from the human breast cancer cell line MDA-MB-468 infected with Ad-IRF-1, we observed a 15-fold down-regulation of the survivin gene when compared with uninfected cells. Consequently, we tested survivin expression in Ad-IRF-1-infected MDA-MB-468 and SK-BR-3 breast cancer cell lines. Immunoblotting analyses supported the contention that ectopic expression of the IRF-1 protein results in down-regulation of survivin protein expression that is independent of p53. In addition, Ad-IRF-1 infection of these human breast cancer cell lines induces the expression of p21. We also report that increased apoptosis is observed in tumor cells infected with Ad-IRF-1 compared with Ad-Psi5 mock-infected cells and that cell death is further augmented when the IRF-1-infected cells are cultured with Adriamycin. Moreover, in a xenogeneic mouse model of breast carcinoma, in vivo treatment of tumor-bearing mice with intratumoral Ad-IRF-1 injections results in tumor growth inhibition. In resected tumors from mice that had been treated with Ad-IRF-1, tumor cells that express the IRF-1 transgene have a predominant IRF-1-positive, survivin-negative phenotype. Collectively, these observations suggest that therapies designed to enhance IRF-1 expression within tumor cells may represent novel treatment strategies for breast cancer.     

A phase I/II trial of rAd/p53 (SCH 58500) gene replacement in recurrent ovarian cancer

PURPOSE: To determine the safety, gene transfer, host immune response, and pharmacokinetics of a replication-deficient adenovirus encoding human, recombinant, wild-type p53 (SCH 58500) delivered into the peritoneal cavity (i.p.) alone and sequentially in combination with platinum-based chemotherapy, of patients with recurrent ovarian, primary peritoneal, or fallopian tube cancer containing aberrant or mutant p53. METHODS: SCH 58500 was administered i.p. to three groups of patients with heavily pretreated recurrent disease. Group 1 (n=17) received a single dose of SCH 58500 escalated from 7.5 x 10(10) to 7.5 x 10(12) particles. Group 2 (n=9) received two or three doses of SCH 58500 given alone for one cycle, and then with chemotherapy for two cycles. The SCH 58500 dose was further escalated to 2.5 x 10(13) particles/dose in group 2. A third group (n=15) received a 5-day regimen of SCH 58500 given at 7.5 x 10(13) particles/dose per day i.p. alone for cycle 1 and then with intravenous carboplatin/paclitaxel chemotherapy for cycles 2 and 3. RESULTS: No dose-limiting toxicity resulted from the delivery of 236/287 (82.2%) planned doses of SCH 58500. Fever, hypotension abdominal complaints, nausea, and vomiting were the most common adverse events. Vector-specific transgene expression in tumor was documented by RT-PCR in cells from both ascitic fluid and tissue biopsies. Despite marked increases in serum adenoviral antibody titers, transgene expression was measurable in 17 of 20 samples obtained after two or three cycles of SCH 58500. Vector was detectable in peritoneal fluid by 24 hours and persisted for as long as 7 days whereas none was detected in urine or stool. There was poor correlation between CT scans and CA125 responses. CA125 responses, defined as a greater than 50% decrement in serum CA125 from baseline, were documented in 8 of 16 women who completed three cycles of the multidose regimen. CONCLUSION: CT scans are not a valid measure of response to i.p. SCH 58500 due to extensive adenoviral-induced inflammatory changes. Intraperitoneal SCH 58500 is safe, well tolerated, and combined with platinum-based chemotherapy can be associated with a significant reduction of serum CA125 in heavily pretreated patients with recurrent ovarian, primary peritoneal, or fallopian tube cancer.     

High bad and bcl-xL gene expression and combined bad,bcl-xL,bax and bcl-2 mRNA levels: molecular predictors for survival of stage 2 soft tissue sarcoma patients

The role of the bcl-2 gene family members in promoting or antagonizing apoptosis in malignant tumors, including soft tissue sarcomas (STS), is well known. However, the impact of mRNA expression of bcl-2 family genes on prognosis has not been thoroughly investigated in STS. Samples from 82 STS patients were analyzed for mRNA expression of bad, bax, bcl-xL and bcl-2 by a high-throughput quantitative RT-PCR approach, using validated assays based on TaqMan technology. The mRNA data, related to glyceraldehyde-3-phosphate dehydrogenase expression measured in the same sample, were analysed for their correlation to tumor stage and overall survival of patients. In a Kaplan-Meier analysis none of the mRNA levels investigated differed significantly with regard to their impact on survival (log-rank test). However, after including the tumor stage in the statistical analysis, a borderline significance was observed for bad mRNA expression (p=0.068) indicating a stage-specific impact of mRNA expression on prognosis. Considering STS patients of tumor stage 2, multivariate Cox analysis revealed that bad mRNA values > or = 10 (p=0.0039; RR=9.08), bcl-xL > or = 1.5 (p=0.067; RR=4.59), bax > or = 0.005 (p=0.1; RR=2.84) and bcl-2 < 3 (p=0.42; RR=1.7) were associated with a poor prognosis. Combined high bad/bcl-xL mRNA expression levels revealed a 20-fold increase in the relative risk of tumor-related death (p=0.016) when comparing the poor and good prognosis groups. There was a 14.5-fold and 6.5-fold increase in the risk for the combinations of high bax/bcl-xL mRNA (p=0.018) and bax/bcl-2 mRNA expression (p=0.017), respectively. In conclusion, high bad mRNA levels and combined values of bad/bcl-xL bax/bcl-xL and bax/bcl-2 appear to be independent prognostic factors at least for stage 2 STS patients. In the combinations of mRNA levels there was more than an additive effect pointing to different pathways of prognostic relevance.     

Derivation and initial characterization of a mouse mammary tumor cell line carrying the polyomavirus middle T antigen: utility in the development of novel cancer therapeutics

Here we describe the derivation of novel cell lines from spontaneous mammary tumors that arose in mouse mammary tumor virus-polyomavirus (MMTV-PyV) Middle T (MidT) transgenic mice. Clonal cell lines from four mixed cell populations were tested for adenovirus transducibility and sensitivity to p53 tumor suppressor gene therapy mediated by SCH58500, a replication-deficient adenovirus that expresses human p53. The MidT2-1 cell line was selected for further characterization in vitro and in vivo. This cell line carried the PyV MidT antigen, had wild-type p53 DNA, and was sensitive to suppression of proliferation by MMAC/PTEN tumor suppressor gene therapy. MidT2-1 cells gave rise to highly aggressive tumors in syngeneic FVB mice in both the mammary fat pad and the peritoneal cavity. The histopathology of MidT2-1 tumors closely resembled the histopathology of the primary transgenic tumors. Tumor growth in vivo was inhibited by p53 gene therapy or by MMAC gene therapy. In addition, combination therapy with a number of anticancer agents had synergistic or additive efficacy in vitro. In particular, MMAC gene therapy synergized with SCH58500 or paclitaxel. In the i.p. MidT2-1 tumor model p53 gene therapy enhanced the survival benefits of paclitaxel/cisplatin chemotherapy. Combination therapy has become a mainstay in cancer treatment. In this report, we use a novel transgenic mouse tumor cell line to suggest new combinations that might be explored in clinical cancer care. These include gene therapy using the tumor suppressors MMAC and p53, chemotherapy using farnesyl transferase inhibitors, the microtubule stabilizing taxanes, and the DNA synthesis disruptors gemcitabine and cisplatin. The precise biological mechanisms by which these therapies induce their antitumor effects are not fully elucidated. However, the work presented here suggests that many of these therapeutic approaches have synergistic antitumor activity when used in combination.     

Expression of bcl-2 and bax in chewing tobacco-induced oral cancers and oral lesions from India

Deregulation of oncogenes and tumor suppressor genes involved in apoptosis has been associated with tumor development and progression. To investigate the involvement of apoptosis regulating proteins in oral cancer in Indian patients, primarily associated with chewing tobacco habits, immunohistochemical expression of bcl-2 and bax was examined in 63 oral squamous cell carcinomas, and 31 putative premalignant lesions. Our studies revealed overexpression of tumor specific cytoplasmic bcl-2 in 56% and bax in 43% oral cancers. The oral cancers in the Indian patients are preceded by premalignant oral lesions; hence oral lesions were examined for bcl-2 and bax expression. We observed aberrant expression of bcl-2 in 16% oral lesions comprising leukoplakias and SMF and bax in 55% oral lesions. We have already reported, p53 expression in these oral cancers and lesions. It was noteworthy that 30% oral cancers demonstrated a p53+bcl2+ pattern, and 14% samples exhibited p53+bcl2+bax+ pattern. However, none of the oral lesions showed concurrent deregulation of p53 and bcl-2 or all the three genes. Interestingly 45% oral lesions were p53-bax+ as compared to 18% oral cancers; while 39% oral lesions were bcl2-bax+ as compared to 14% oral cancers, indicating overexpression of bax in oral lesions, in the absence of p53 and bcl-2 proteins. Significant correlation was observed between positive nodal status and bcl2+ (p=0.047) and p53+bcl-2+ (p=0.01) in oral cancers. Kaplan Meier survival analysis showed significantly (p=0.059) higher survival in patients with p53- oral tumors than with p53+ tumors. Our studies thus indicate frequent overexpression of apoptosis regulators bcl-2, bax and p53 proteins in oral cancers, and a subset of oral lesions, representing early events in oral car-cinogenesis. The aberrant bcl-2 expression and loss of p53 function observed, may play an important role in the tumorigenesis of oral cancers by allowing escape from apoptosis and enabling additional genetic alterations to accrue.     

Long term follow-up of patients with recurrent ovarian cancer after Ad p53 gene replacement with SCH 58500

OBJECTIVE: We have previously reported the safety, efficient gene transfer, and favorable CA125 responses of individuals with recurrent ovarian cancer treated by p53 gene replacement with the adenoviral vector SCH 58500. The purpose of the present investigation was to evaluate the long-term follow-up of these heavily pretreated patients subsequent to SCH 58500 dosing. METHODS: Patients (n=36) were treated with either single-dose SCH 58500 in the phase I study or with multiple doses (MD) of SCH 58500 over multiple cycles in combination of platinum-based chemotherapy in the phase I/II portion of the study. Five patients were initially treated in the single-dose group and re-enrolled in the MD group. The MD group was evaluated both without the re-enrolled patients as MD1 (n=19), and as MD2 (n=24), which included them. Patients who were only treated on the single-dose arm were designated as SD (n=12). Most patients received additional chemotherapy at the discretion of their physicians on completion of the trial. The current analysis is a retrospective sequential cohort survival analysis. RESULTS: The first patient was treated in March 1997 and the last patient completed SCH 58500 in September 1998. There was no difference in age at diagnosis, Karnofsky performance status, interval between diagnosis to SCH 58500, prior cycles or regimen of chemotherapy, platinum-free interval, percent platinum refractory patients, pretreatment CA125, or largest tumor volume between groups. Both MD groups had a slightly longer chemotherapy-free interval before SCH 58500 than the SD group. Median survival of individuals who received MD SCH 58500 with chemotherapy was 12-13.0 months, compared to only 5 months for those treated with SD SCH 58500. There are 10 long-term survivors more than 20 months after MD treatment for recurrent disease compared to only 2 long-term survivors after SD SCH 58500. CONCLUSION: The 12- to 13.0-month median survival in a heavily pretreated population with recurrent ovarian cancer compares favorably to the 16-month median survival for individuals treated with paclitaxel at the time of initial recurrence of this disease and is more than double the 5-month survival seen with palliative radiotherapy or paclitaxel failure. These data suggest that further study of SCH58500 is clearly indicated.     

Response and determinants of sensitivity to paclitaxel in human non-small cell lung cancer tumors heterotransplanted in nude mice.

The lack of tumor models that can reliably predict for response to anticancer agents remains a major deficiency in the field of experimental cancer therapy. Although heterotransplants of certain human solid tumors can be successfully grown in nude mice, they have never been appropriately explored for prediction of in vivo chemosensitivity to anticancer agents. We determined the tumor response rate and studied the influence of several biological and molecular tumor parameters on the in vivo sensitivity to paclitaxel in a series of heterotransplanted human non-small cell lung cancer (NSCLC) tumors. One hundred consecutive resected NSCLC tumors were heterotransplanted s.c. in nude mice. The in vivo sensitivity to i.v. paclitaxel (60 mg/kg every 3 weeks) was studied in 34 successfully grown heterotransplants. Treatment started when the tumors reached a size of 5 mm in diameter, and strict standard clinical criteria (>50% shrinkage in tumor weight or cross-sectional surface) were used to define tumor response. Baseline multidrug resistance protein (MRP), Her-2/neu, and epidermal growth factor receptor (EGFR) expression, and pre- and posttherapy bax and bcl-2 expression were determined by Western blot analysis. p53 status was determined by sequencing. The overall take rate was 46% (95% confidence interval, 36-56%) and was significantly higher (P < 0.05) for squamous carcinoma tumors (75%) than for adenocarcinoma tumors (30%) and bronchoalveolar tumors (23%). The heterotransplants were morphologically very similar to the original tumors. The response rate to paclitaxel was 21% (95% confidence interval, 9-38%). Baseline tumor parameters associated with response were no Her-2/neu expression (none of the responding tumors expressed Her-2/neu versus 48% of the nonresponding tumors, P = 0.05) and baseline bcl-2 expression (all responding tumors expressed bcl-2 versus only 43% of the nonresponding tumors, P = 0.02). There was a trend toward a higher response rate in bax-positive tumors, and MRP- and EGFR-negative tumors, but it was not statistically significant. The response was independent of baseline p53 status and baseline mitotic index. Responding tumors had a higher bax/bcl-2 ratio 24 h after therapy, but the difference was only marginally significant (2.8 for responding tumors versus 1.1 for nonresponding tumors, P = 0.07). The extent of mitotic arrest at 24 h after therapy was not associated with response. Human NSCLC heterotransplants are morphologically identical to the original tumors and have a response rate to paclitaxel that is equivalent to that reported in Phase II studies in patients with advanced NSCLC treated with single-agent paclitaxel. NSCLC heterotransplants deserve to be explored to evaluate new agents for lung cancer and to predict clinical response on an individual basis in selected groups of patients.     

Expression of apoptosis-related proteins (p53, p21WAF1, bcl-2, and bax) and sensitivity to chemotherapy in squamous cell carcinoma of the esophagus

Background. Chemotherapy is an important component of the multimodal approach to the treatment of advanced esophageal squamous cell carcinoma. Methods. We investigated the associations between p53, p21 (Waf1), bcl-2, and bax expression and response to chemotherapy (cisplatin + 5-fluorouracil + leucovorin) in 43 patients with advanced esophageal squamous cell carcinoma. The expression of p53, p21 (Waf1), bcl-2, and bax proteins was analyzed immunohistologically in pretreatment biopsy and post-treatment resected specimens. Results. The 23 patients who had objective evidence of either a complete response (CR) or a partial response (PR) to chemotherapy survived for significantly longer than the 20 patients who had no response (NR). The expression of p53, p21 (Waf1), bcl-2, and bax was detected in 26 (61%), 12 (28%), 6 (14%), and 19 (44%) of the pretreatment biopsy specimens, respectively. The response to chemotherapy was not independently associated with the expression of any of these proteins. However, in the 26 patients with p53-expressing tumors, the response rate was 80% in patients whose tumor also expressed p21, whereas it was 19% in those whose tumor did not coexpress p21. No change in p53 expression was observed before and after chemotherapy, except in 1 patient; however, p21 expression appeared to be induced by chemotherapy in 5 patients. Patient survival was also not independently associated with the expression of any of these proteins. However, patients with p53-negative or p21-positive tumors had a better response to chemotherapy and survived for longer than those with p53-positive and p21-negative tumors. Conclusion. p53 and p21 expression in biopsy specimens obtained before chemotherapy could be useful predictors of response and survival in patients with advanced esophageal squamous cell carcinoma. Received: April 14, 1999 / Accepted: November 8, 1999     

紫杉醇对人骨肉瘤细胞凋亡及对bcl-2 、bax基因表达的影响

 目的 了解紫杉醇诱导人骨肉瘤细胞的凋亡效果,以及凋亡与bcl-2和bax表达之间的关系。方法 用不同浓度的紫杉醇作用于骨肉瘤细胞MG63。采用胎盼蓝染色法,于细胞记数板进行活细胞率检测计算。采用光镜和电子显微镜对细胞形态改变进行观测,采用原位缺口末端标记凋亡检测法（TUNEL）和流式细胞术（Annexin-V-FITC＆PI）对细胞凋亡进行检测。采用免疫组织化学法对凋亡调节基因bcl-2和bax表达进行检测。结果 骨肉瘤活细胞率随着紫杉醇作用时间延长和浓度增高而降低。紫杉醇诱导骨肉瘤细胞MG63凋亡表现为典型的凋亡特征,包括：细胞形态学改变,细胞染色质浓聚,染色质新月形变,胞核碎裂等。TUNEL法检测到了细胞DNA片段的断裂。随着细胞凋亡的发生,开始出现G2/M期阻滞。紫杉醇可以降低凋亡相关基因bcl-2的表达和增加bax基因的表达。结论 紫杉醇可以通过时间依赖性和剂量依赖性方式,促使细胞G2/M期阻滞和抑制细胞有丝分裂,从而诱导人骨肉瘤细胞凋亡。这种凋亡可能受到凋亡相关基因bcl-2低表达和bax高表达的调控。     

Proliferation and Apoptosis in Long-term Surviving Low Grade Gliomas in Relation to Radiotherapy

Identification of patients with a low grade glioma with a long-term recurrence-free survival is of clinical value as radiotherapy can be postponed until recurrence. The recurring glioma may increase in malignancy compared to the original tumor, which is possibly related to radiotherapy. We studied proliferation by counting mitotic figures and by MIB-1 labeling, apoptosis by TUNEL and expression of proteins related to cell cycle regulation by immunohistochemical analysis of p53, p21, bcl-2 and bax expression in 48 low grade gliomas. Astrocytomas (A, n = 14) and oligodendrogliomas (O, n = 4) with a recurrence-free survival of more than 9 years after surgery had a significantly lower p53 index compared to A (n = 18) and O (n = 12) with a histopathologically documented recurrence. Additionally, the recurrence-free A had a higher p21 index. No significant differences were observed in MIB-LI, TUNEL-LI, bcl-2 and bax expression. Initially low grade gliomas and their corresponding recurrences were compared (n = 30). In the gliomas without radiotherapy (n = 15), no differences in mitotic rate, TUNEL-LI, p53, p21, bcl-2 and bax expression were found between primary tumors and their recurrences. Only MIB-LI was higher in the recurrent tumors. In the gliomas with radiotherapy (n = 15) no differences were detected in these parameters between the original tumor and the recurrent tumor except for a higher number of mitoses in the recurrent tumors. We conclude that low grade gliomas with a long-term recurrence-free survival were characterized by a low p53 protein expression and, in the case of A, a higher p21 index. We found no evidence that radiotherapy is involved in changes of proliferation, apoptosis or expression of proteins related to cell cycle regulation in recurring gliomas.     

NK cells mediate the anti-tumor effects of E1-deleted, type 5 adenovirus in a human tumor xenograft model

SCH58500 (ACN53) is a recombinant adenovirus expressing human p53 for gene therapy of cancer. In preclinical studies, SCH58500 has shown efficacy against many tumor-types with non-functional p53. This activity arises from both p53-mediated and adenovirus vector-mediated mechanisms. The importance of NK cells for adenovirus-mediated tumor suppression after intratumoral dosing was demonstrated using MDA-MB-231 human breast cancer xenografts in scid (defective T and B cell response) and scid-beige (defective T, B, and NK cell response) mice. There was no adenovirus vector-mediated anti-tumor activity in scid-beige mice. Dexamethasone (Dex) is a potent suppressor of the cellular immune response to recombinant adenovirus in mice and rats. Dex abolished growth suppression caused by adenovirus vector, but did not interfere with the anti-tumor efficacy of p53. Supression of NK cell activity in scid mice using intravenous administration of a neutralizing antibody had the same effect as Dex. These data support a role for NK cells in adenovirus vector-mediated anti-tumor efficacy.