Katsumi Nakatomi

Reversal of breast cancer resistance protein (BCRP/ABCG2)-mediated drug resistance by novobiocin, a coumermycin antibiotic

Breast cancer resistance protein (BCRP/ABCG2) of an ATP‐binding cassette half‐transporter confers resistance against mitoxantrone and camptothecin derivatives of topotecan and irinotecan. Novobiocin, a coumermycin antibiotic, is known to enhance anticancer drug sensitivity of cancer cells in vitro and in vivo, the mechanism of which remains undetermined. Here we focused on drug efflux pump and examined whether novobiocin reversed drug resistance in multidrug‐resistant cells highly expressing BCRP. To explore the reversal mechanisms, intracellular drug accumulation was measured by flow cytometry, and a topotecan transport study using plasma membrane vesicles was performed. We used PC‐6/SN2‐5H2 small cell lung cancer and MCF‐7/MX breast cancer cells selected with SN‐38 of the active irinotecan metabolite and mitoxantrone, respectively, and the BCRP cDNA transfectant MCF‐7/clone 8 cells. These cells expressed high levels of BCRP mRNA but not other known transporters. Compared to the parental PC‐6 cells, PC‐6/SN2‐5H2 cells were 141‐, 173‐ and 57.2‐fold resistant to topotecan, SN‐38 and mitoxantrone, respectively. Novobiocin at 60 μM decreased the degree of the above resistance by approximately 26‐fold in PC‐6/SN2‐5H2 cells, and similarly reversed resistance in MCF‐7/MX, MCF‐7/clone 8 and un‐selected NCI‐H460 cells highly expressing BCRP. Furthermore, novobiocin increased the intracellular topotecan accumulation in these cells and inhibited the topotecan transport into the membrane vesicles of PC‐6/SN2‐5H2 cells. No effects of novobiocin in these assay were observed in the parental PC‐6 and MCF‐7 cells. The kinetic parameters in the transport study indicated that novobiocin was a inhibitor for BCRP, resulting in competitive inhibition of BCRP‐mediated topotecan transport. These findings suggest that novobiocin effectively overcomes BCRP‐mediated drug resistance at acceptable concentrations.

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.

Antiproliferative effects of the histone deacetylase inhibitor FR901228 on small-cell lung cancer lines and drug-resistant sublines

FR901228 is a novel histone deacetylase (HDAC) inhibitor, and its antiproliferative effects on non‐small cell lung cancer cells have been shown in vitro. However, there have been no reports concerning the effects on small‐cell lung cancer (SCLC). We have recently demonstrated that the HDAC inhibitors trichostatin A and sodium butyrate inhibit expression of the catalytic subunit of telomerase (hTERT) mRNA and telomerase activity in prostate cancer cells. The present study was designed to evaluate the effects of FR901228 on proliferation and telomerase activity in SCLC cells in vitro. FR901228 at 5 to 10 nM increased the fraction of cells in the G2/M and sub‐G1 phases of the cell‐cycle, and inhibited the growth of H69, H526 and H82 cell lines. The expression of hTERT mRNA was inhibited 6 hr after treatment, prior to obvious inhibition of cell growth or cell‐cycle distribution shifts. The inhibition of hTERT mRNA expression and telomerase activity was not a consequence of cell‐growth arrest or apoptosis. Cycloheximide blocked the suppression of hTERT mRNA induced by FR901228, and the inhibition of hTERT mRNA by FR901228 required newly synthesized proteins. FR901228 also effectively inhibited growth of etoposide‐resistant UMCC‐1/VP‐16, irinotecan‐resistant PC‐6/SN2‐5H and cisplatin‐resistant H526/CDDP cells having decreased expression of hTERT mRNA and telomerase activity, as well as their parental cells. This implies that SCLC resistant to these key drugs are not cross‐resistant to FR901228. The present study suggests that FR901228 may be a promising drug for chemotherapy of cancers including SCLC, even for refractory or relapsing tumors after conventional chemotherapy.

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.

Methylation status of breast cancer resistance protein detected by methylation-specific polymerase chain reaction analysis is correlated inversely with its expression in drug-resistant lung cancer cells

Breast cancer resistance protein (BCRP) functions as a drug efflux transporter that mediates drug resistance. Topoisomerase I inhibitors, including 7‐ethyl‐10‐hydroxycamptothecin (SN‐38), are substrates effluxed by BCRP. However, it remains unclear whether the overexpression of BCRP induces drug resistance during chemotherapy. The objectives of the current study were to examine a correlation of altered promoter methylation of BCRP with BCRP expression and to investigate the correlation between methylation status according to methylation‐specific polymerase chain reaction (MSP) analysis and BCRP expression levels in several small cell and nonsmall cell lung cancer cells.

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.

Randomized Phase II Trial of Irinotecan with Paclitaxel or Gemcitabine for Non-small Cell Lung Cancer Association of UGT1A1*6 and UGT1A1*27 with Severe Neutropenia

Hypothesis: Irinotecan-containing regimens are known to be active and tolerable in patients with non-small cell lung cancer (NSCLC). A randomized phase II trial was conducted to evaluate the efficacy of irinotecan plus paclitaxel or gemcitabine for previously untreated stage IIIB or stage IV NSCLC. Patients and Methods: Previously untreated patients with adequate organ function who gave written informed consent were randomly assigned to receive irinotecan (50 mg/m2 on days 1, 8, and 15) plus paclitaxel (180 mg/m2 on day 1) every 4 weeks (IP group) or irinotecan (100 mg/m2 on days 1 and 8) plus gemcitabine (1000 mg/m2 on days 1 and 8) every 3 weeks (IG group). The primary endpoint was the response rate. We also evaluated the relationship of response and toxicity to polymorphisms of the uridine diphosphate glucuronosyltransferase (UGT) gene. Results: Eighty patients were enrolled, and 78 patients were eligible (38 in the IP group and 40 in the IG group). The response rate was 31.6% (95% confidence interval: 17.5–48.7%) in the IP group and 20.0% (9.1–35.6%) in the IG group. The median progression-free survival time was 86 days and 145 days, respectively. Both regimens were well tolerated. The most common severe adverse event was grade 4 neutropenia (36.8% and 10.0%, respectively), which was associated with UGT1A1*6 and UGT1A1*27. UGT polymorphisms did not correlate with response. Conclusions: Irinotecan plus paclitaxel may be more active against NSCLC than irinotecan plus gemcitabine. The UGT1A1*6 and UGT1A1*27 genotypes might be useful predictors of grade 4 neutropenia in patients who receive irinotecan-based chemotherapy.

Mapping of the wet/dry earwax locus to the pericentromeric region of chromosome 16

Human earwax is a one-gene trait comprising two phenotypically distinct forms--wet and dry. This trait is attributed to secretory products of the ceruminous apocrine glands, and frequencies of phenotypes vary between ethnic groups. We did linkage analysis of eight Japanese families segregating earwax dimorphism. We assigned the earwax locus within a approximately 7.42-cM region between the loci D16S3093 and D16S3080 on chromosome 16p11.2-16q12.1, with a maximum two-point LOD score of 11.15 (theta;=0.00) at the locus D16S3044. Identification of the earwax locus could contribute to further anthropogenetic studies and physiological and pathological understanding of the apocrine-gland development.

Analysis of intratumor heterogeneity of EGFR mutations in mixed type lung adenocarcinoma.

BACKGROUND Epidermal growth factor receptor mutations are predictive of the success of EGFR tyrosine kinase inhibitor treatment in patients with advanced non--small-cell lung cancer. As with other solid tumors, lung cancer is thought to be the result of an accumulation of genetic alterations after exposure to carcinogens. The aim of the present study was to clarify the relationship between multistep carcinogenesis and the accumulation of EGFR mutations. PATIENTS AND METHODS The intratumor heterogeneity of EGFR mutations was analyzed in 38 patients with resected mixed-type lung adenocarcinoma according to histological patterns, and the clinical features of the patients harboring intratumor heterogeneity of EGFR mutations were evaluated. RESULTS Intratumor heterogeneity of EGFR mutations was detected in 9 of 38 tumors. EGFR mutations were more common in the bronchioloalveolar (lepidic) carcinoma pattern than in the papillary and acinar patterns, although this difference was not significant. However, there was a significant correlation between intratumor heterogeneity of EGFR mutations and smoking history (P < .043). CONCLUSION Intratumor heterogeneity of EGFR mutations correlates with the distribution of histological subtype in mixed type adenocarcinoma and is associated with smoking history.

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.