Shigeru Kawabata

Histone deacetylase inhibitors suppress telomerase reverse transcriptase mRNA expression in prostate cancer cells.

Telomerase activity is involved in cellular immortality. We have recently demonstrated that telomerase activity is closely associated with cell proliferation in prostate cancers. Telomerase is composed primarily of the catalytic subunit (hTERT) and the RNA template (hTERC), and hTERT expression is regulated by several factors such as c‐MYC and p21Waf1. Histone deacetylase (HDAC) inhibitors are known to modulate transcription and exhibit antiproliferative effects on cancer cells. The present study was designed to evaluate the effects of HDAC inhibitors on hTERT mRNA expression in prostate cancer cells. LNCaP and PC‐3 cells were treated with HDAC inhibitors, trichostatin A (TSA) and sodium butyrate (NaB); mRNA expression and telomerase activity were evaluated by RT‐PCR and the TRAP assay, respectively. In LNCaP cells, hTERT mRNA expression was suppressed at 1 and 3 hr after treatment with 1 μM TSA and 4 mM NaB, respectively, followed by inhibition of telomerase activity. The inhibition of hTERT mRNA expression preceded suppression of cell proliferation. In PC‐3 cells, TSA and NaB also inhibited cell proliferation, hTERT mRNA expression and telomerase activity. In both cell lines, TSA and NaB had no effect on hTERC expression, or on expression of c‐myc and p21Waf1 mRNA. These effects of TSA and NaB were unlikely to be consequences of cell cycle arrest, apoptosis, or cell differentiation. Thus, HDAC inhibitors down‐regulated telomerase activity via suppression of hTERT mRNA expression. Our study identified a novel mechanism for the antiproliferative effects of HDAC inhibitors on prostate cancer cells.

Interactions of ofloxacin and erythromycin with the multidrug resistance protein (MRP) in MRP-overexpressing human leukemia cells.

ABSTRACT To investigate interactions between the multidrug resistance protein (MRP) and antimicrobial agents, we examined the effects of 12 agents on vincristine sensitivity and efflux of the calcein acetoxy-methyl ester (calcein-AM) of a MRP substrate in MRP-overexpressing cells. Only ofloxacin and erythromycin enhanced sensitivity with increased intracellular vincristine accumulation and inhibited the calcein-AM efflux. Our findings suggest that the two agents are possible MRP substrates and may competitively inhibit MRP function as a drug efflux pump.

Interruption of p16 gene expression in adult T-cell leukaemia/lymphoma: clinical correlation

Summary. We previously reported that p16 gene deletion is involved in the development and progression of adult T‐cell leukaemia/lymphoma (ATLL). To further investigate the significance of this gene in ATLL, we examined its expression status in 63 patients. Samples were analysed at DNA, mRNA and protein levels using real‐time polymerase chain reaction (PCR), reverse transcription (RT)‐coupled real‐time PCR and Western blot respectively. Twenty‐four patients (38·1%) were p16 gene negative, and they showed significantly shorter survival than p16‐gene‐positive patients. The expression of p16 mRNA in p16‐gene‐positive patients varied greatly, and cells from some patients showed up to several hundredfold higher expression than normal lymphocytes. Surprisingly, among 17 patients examined for p16 protein expression, all four patients with unusually high mRNA lacked p16 protein expression, indicating that p16 protein production in these patients was interrupted at the translational level. Moreover, these patients showed significantly shorter survival than p16‐protein‐positive patients. These results indicate that the presence of p16 gene and p16 mRNA do not necessarily indicate the production of p16 protein in ATLL, and that loss of p16 protein function is involved in progression of ATLL.

Phase I study of irinotecan and cisplatin with concurrent split-course radiotherapy in limited-disease small-cell lung cancer.

We conducted a phase I study of irinotecan (CPT-11) and cisplatin with concurrent split-course radiotherapy in limited-disease small-cell lung cancer (LD-SCLC). This study aimed to determine the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT) of this therapy. Four chemotherapy cycles of CPT-11 (days 1, 8 and 15) and cisplatin (day 1) were repeated every 28 days. Radiotherapy of 2 Gy/day commenced on day 2 of each chemotherapy cycle with 20 Gy administered from the first to the third cycles (a total of 60 Gy). 17 patients were enrolled at three dose levels (CPT-11/cisplatin: 40/60, 50/60 and 60/60 mg/m(2)), and 16 were evaluable for toxicity and outcome. 2 of 4 patients at 60/60 mg/m(2) refused continuation of therapy because of general fatigue, and the relative dose intensity of CPT-11 at 50/60 mg/m(2) was approximately 50%. These levels were considered as the MTD. Tumour responses included four complete responses (CR), 11 partial responses (PR) and one no change (NC), and the overall response rate was 93.8% (95% confidence interval: (CI) 71.7-98.9%). This combined modality is tolerable, and CPT-11/cisplatin of 40/60 mg/m(2) in this modality is recommended for phase II study.

Autoantibody to heat shock protein Hsp40 in sera of lung cancer patients

Heat shock protein Hsp40 is a stress protein with chaperone activity and has a cooperative function with Hsp70 in mammalian cells. We examined the possible expression of Hsp40 in lung tumor tissues using immunoblotting and immunohistochemistry, and established an enzyme‐linked immuno‐sorbent assay (ELISA) method to detect IgG antibody to Hsp40 in the serum using purified human Hsp40. Sera were obtained from 130 normal subjects and 50 patients with lung cancer. Lung tumor tissues and cells specifically overexpressed Hsp40, and no such expression was detected in normal lung tissues. Compared with normal sera, significantly higher levels of auto‐antibody to Hsp40 were present in patients with lung cancer. The present study is the first to demonstrate overexpression of Hsp40 in human tumor tissue and the associated presence of autoantibody to Hsp40 in the serum. These results suggest that overexpression of Hsp40 in tumor cells may be recognized as a self‐antigen.

Effects of Renal Function on Pharmacokinetics of Recombinant Human Granulocyte Colony-Stimulating Factor in Lung Cancer Patients

ABSTRACT Animal studies suggest that the kidney is involved in the elimination of recombinant human granulocyte colony-stimulating factor (rhG-CSF), which is used for patients with neutropenia during cancer chemotherapy. Since anticancer drugs induce nephrotoxicity, it is important to clarify the role of the kidney in the pharmacokinetics of rhG-CSF in cancer patients. Our study was designed to evaluate the relationship between the pharmacokinetics of rhG-CSF and renal function in lung cancer patients compared to the absolute neutrophil count (ANC). The pharmacokinetic studies were conducted with 25 lung cancer patients. Following chemotherapy using platinum-based compounds, a bolus 5 μg of rhG-CSF/kg of body weight was intravenously injected from the first day of leukopenia or neutropenia. Pharmacokinetic parameters were estimated by fitting the concentration in serum-time data to a two-compartment model according to the population pharmacokinetics and the Bayesian method. Creatinine clearance (CLCR) was predicted by the Cockcroft-Gault formula. rhG-CSF clearance (CLG-CSF) correlated significantly with the ANC (r = 0.613; P < 0.001) and CLCR (r = 0.632; P < 0.001). Multiple linear regression analysis showed that the combination of the ANC and CLCR accounted for 57.4% of the variation of CLG-CSF. In patients with an ANC of <1,000/μl, CLCR accounted for 72.9% of the variation of CLG-CSF (P < 0.001). Our findings suggest that renal function and neutrophil counts correlate with CLG-CSF and that the role of renal function in eliminating rhG-CSF is important in lung cancer patients with neutropenia.

Phase I and pharmacokinetic study of paclitaxel and irinotecan for patients with advanced non-small cell lung cancer.

We conducted a phase I study of paclitaxel and irinotecan (CPT-11) in advanced non-small cell lung cancer (NSCLC). This study aimed to determine the maximum tolerated doses (MTD). The pharmacokinetics of CPT-11 and its major active metabolite, SN-38, were also analysed. Patients received paclitaxel (day 1) followed by CPT-11 (days 1, 8 and 15), in a 4-week cycle, and paclitaxel and CPT-11 were escalated from 120 and 40 mg/m(2), respectively. 28 patients were enrolled, who were evaluated for toxicity. 2 of 6 patients at 210 mg/m(2) paclitaxel and 50 mg/m(2) CPT-11, and 2 of 4 at 180 and 60 mg/m(2) developed dose-limiting toxicity (DLT) (neutropenia, fever, neurotoxicity and diarrhoea). The area under the plasma concentration-time curve (AUC) of CPT-11 on day 1 was significantly higher than that on days 8 or 15 at each dose level (P=0.002). The AUC of SN-38 on day 1 was significantly increased using paclitaxel doses >or=150 mg/m(2). A preceding paclitaxel administration changed the pharmacokinetics of CPT-11 and SN-38. However, the toxicity was tolerable. Paclitaxel 180 mg/m(2) and CPT-11 50 mg/m(2) were the recommended doses for further phase II study of this combination.

Birth Cohort Effects on Incidence of Lung Cancers: A Population‐based Study in Nagasaki, Japan

Smoking prevalence remains high (around 60%) among Japanese males, but smoking initiation among males born in the 1930s decreased by approximately 10% due to economic difficulties following World War II. The present study was designed to examine whether this temporary decline in smoking initiation influenced the subsequent incidence of lung cancers, especially adenocarcinoma. Trends of lung cancer incidence by histological type in both sexes were investigated using data from the population‐based cancer registry in Nagasaki, Japan, from 1986 through 1995. During this period, 5668 males and 2309 females were diagnosed as having lung cancer, and the overall incidence of lung cancers among both sexes remained stable. However, males aged 55–59 years showed a decrease in the age‐specific incidence of adenocarcinoma and squamous‐cell carcinoma (P < 0.05 and P < 0.01, respectively). In birth cohort analyses, the incidence of adenocarcinoma and squamous‐cell carcinoma was lower in the 1935–1939 birth male cohort than in the successive cohorts. The incidence of lung cancers among females with low smoking prevalence did not change with birth cohort. The low smoking initiation among the 1935–1939 birth male cohort appeared to have resulted in a decreased incidence of adenocarcinoma and squamous cell carcinoma among middle‐aged Japanese males. The present study suggests that smoking prevention has an effect in reducing the incidence of lung adenocarcinoma, as well as squamous‐cell carcinoma, among smokers.