Inhibition of multidrug resistance by SV40 pseudovirion delivery of an antigene peptide nucleic acid (PNA) in cultured cells.

Peptide nucleic acid (PNA) is known to bind with extraordinarily high affinity and sequence-specificity to complementary nucleic acid sequences and can be used to suppress gene expression. However, effective delivery into cells is a major obstacle to the development of PNA for gene therapy applications. Here, we present a novel method for the in vitro delivery of antigene PNA to cells. By using a nucleocapsid protein derived from Simian virus 40, we have been able to package PNA into pseudovirions, facilitating the delivery of the packaged PNA into cells. We demonstrate that this system can be used effectively to suppress gene expression associated with multidrug resistance in cancer cells, as shown by RT-PCR, flow cytometry, Western blotting, and cell viability under chemotherapy. The combination of PNA with the SV40-based delivery system is a method for suppressing a gene of interest that could be broadly applied to numerous targets.

Elevated expression of TMEM205, a hypothetical membrane protein, is associated with cisplatin resistance.

Development of cisplatin resistance in cancer cells appears to be a consequence of multiple epigenetic alterations in genes involved in DNA damage repair, proto-oncogenes, apoptosis, transporters, transcription factors, etc. In this study, we found that expression of the hypothetical transmembrane protein TMEM205 (previously known as MBC3205) is associated with cisplatin resistance. TMEM205 was first detected by functional cloning from a retroviral cDNA library made from human cisplatin-resistant (CP-r) cells. TMEM205 is predicted to be a transmembrane protein, but its expression, localization, and function have not previously been investigated. A polyclonal antibody directed to the TMEM205 protein was raised in our laboratory. Using this antibody, it was demonstrated that this protein is located at the cell surface. Its expression is increased in our cisplatin-selected CP-r cell lines, as demonstrated by immunoblotting, confocal examination, and immuno-electron microscopy. Stable transfection of the TMEM205 gene confers resistance to cisplatin by approximately 2.5-fold. Uptake assays with Alexa Fluor-cisplatin showed reduced accumulation in CP-r KB-CP.3 and KB-CP.5 cells, and in TMEM205-transfected cells. Analysis of TMEM205 expression profiles in normal human tissues indicates a differential expression pattern with higher expression levels in the liver, pancreas, and adrenal glands. These results indicate that a novel mechanism for cisplatin resistance is mediated by TMEM205, and also suggest that overexpression of TMEM205 in CP-r cells may be valuable as a biomarker or target in cancer chemotherapy.

[Analysis of patients with locally advanced gastric cancer undergoing gastrectomy after pre-operative chemotherapy including S-1].

To improve the prognosis of advanced gastric cancer, various adjuvant therapies were tried. We retrospectively examined 7 cases of gastrectomy after pre-operative chemotherapy using S-1+CDDP, and reported its effectiveness and the result. An adverse event of more than Grade 3 showed neutropenia in two cases. Anti-tumor effect on the imaging was found in 6 cases of PR and one case of SD. We performed gastrectomy within 4 weeks after completion of chemotherapy in each case. The histological antitumor effect was more than Grade 2 in four cases, but there was no complete response. We compared the overall survival of a patient of more than Grade 2 by histological antitumor effect under grade 1b. In the former, MST was 982 days and the two-year survival rate was 50.0%; in the latter, MST was 443 days and the two-year survival rate was 33.3%. We can perform pre-operative chemotherapy using S-1+CDDP and expect prognostic improvement for a histologically effective case of chemotherapy. If the utility of preoperative chemotherapy mainly with S-1 is proved in a phase III trial, this would appear to be a therapy of choice for advanced gastric cancer in future.

Cronkhite-Canada syndrome complicated with huge intramucosal gastric cancer.

Cronkhite-Canada syndrome (CCS) is a rare nonhereditary disorder with gastrointestinal polyposis and associated ectodermal changes. This report documents a 59-year-old Japanese man with CCS who underwent a total gastrectomy for gastric tumors. The resected specimen showed a huge gastric adenocarcinoma with numerous polyps throughout the stomach. The cancer was pathologically limited to within the mucosa and its histological structure resembled that of hyperplasia in CCS polyps, which led us to suppose that the carcinoma had arisen from hyperplastic CCS polyps. These results urged us to study the phenotypic expression of mucins, which revealed MUC2(-) and MUC5AC(+) and supported the diagnosis of the tumor as a gastric-type well-differentiate adenocarcinoma. A literature search revealed that 32 gastric carcinomas which developed in patients with CCS were mostly limited to within the submucosa in spite of their huge sizes, and such cancer development in CCS polyposis is therefore not considered to be unusual.

Down-regulation of cIAP2 enhances 5-FU sensitivity through the apoptotic pathway in human colon cancer cells.

Currently 5-fluorouracil (5-FU) plays a central role in the chemotherapeutic regimens for colorectal cancers and thus it is important to understand the mechanisms that determine 5-FU sensitivity. The expression profiles of human colon cancer cell line DLD-1, its 5-FU-resistant subclone DLD-1/FU and a further 21 types of colon cancer cell lines were compared to identify the novel genes defining the sensitivity to 5-FU and to estimate which population of genes is responsible for 5-FU sensitivity. In the hierarchical clustering, DLD-1 and DLD-1/FU were most closely clustered despite over 100 times difference in their 50% inhibitory concentration of 5-FU. In DLD-1/FU, the population of genes differentially expressed compared to DLD-1 was limited to 3.3%, although it ranged from 4.8% to 24.0% in the other 21 cell lines, thus indicating that the difference of 5-FU sensitivity was defined by a limited number of genes. Next, the role of the cellular inhibitor of apoptosis 2 (cIAP2) gene, which was up-regulated in DLD-1/FU, was investigated for 5-FU resistance using RNA interference. The down-regulation of cIAP2 efficiently enhanced 5-FU sensitivity, the activation of caspase 3/7 and apoptosis under exposure to 5-FU. The immunohistochemistry of cIAP2 in cancer and corresponding normal tissues from colorectal cancer patients in stage III revealed that cIAP2 was more frequently expressed in cancer tissues than in normal tissues, and cIAP2-positive patients had a trend toward early recurrence after fluorouracil-based chemotherapy. Although the association between drug sensitivity and the IAP family in colorectal cancer has not yet been discussed, cIAP2 may therefore play an important role as a target therapy in colorectal cancer.

Cancer-associated splicing variants of the CDCA1 and MSMB genes expressed in cancer cell lines and surgically resected gastric cancer tissues.

BACKGROUND: Alternative splicing is a molecular mechanism by which different combinations of exons can be alternatively spliced to produce different mRNA isoforms. Recently, several databases have been published to predict the alternative splicing of mRNA; cancer-specific alternative splicing has also been predicted with these databases. Those variants may be potentially useful targets for cancer therapy, however, the accuracy and veracity of these databases have yet to be confirmed. METHODS: In this study, we analyzed 17 genes by reverse transcriptase-polymerase chain reaction (RT-PCR) that were predicted to have cancer-specific alternative splicing by using the splicing database, the Alternative Splicing Annotation Project (ASAP) by Lee et al, between 38 cancer cell lines from various organs and 9 corresponding normal tissues. By designing 2 types of primer sets for RT-PCR including (1) primers flanking the alternatively spliced exons and (2) primers spanning the exon/exon junctions, cancer-associated splicing variants were investigated. RESULTS: The alternatively splicing events were detected in 15 of 17 genes (88%); 35 of 43 variants (81%) were detected successfully with RT-PCR. Among these variants, M-RIP, HYAL2, CDCA1, and MSMB genes showed differential expressions between cancer cell lines and corresponding normal tissues. Furthermore, RT-PCR with surgically resected gastric cancer tissues (diffuse type, 6; intestinal type, 4) confirmed that 2 variants of CDCA1 were upregulated in cancer tissues, whereas both variants of MSMB were expressed predominantly in normal tissues. CONCLUSION: Alternative splicing variants, especially in CDCA1, were detected in this study and may be potentially useful as diagnostic markers and/or novel targets for anticancer therapy.

Profiling SLCO and SLC22 genes in the NCI-60 cancer cell lines to identify drug uptake transporters.

Molecular and pharmacologic profiling of the NCI-60 cell panel offers the possibility of identifying pathways involved in drug resistance or sensitivity. Of these, decreased uptake of anticancer drugs mediated by efflux transporters represents one of the best studied mechanisms. Previous studies have also shown that uptake transporters can influence cytotoxicity by altering the cellular uptake of anticancer drugs. Using quantitative real-time PCR, we measured the mRNA expression of two solute carrier (SLC) families, the organic cation/zwitterion transporters (SLC22 family) and the organic anion transporters (SLCO family), totaling 23 genes in normal tissues and the NCI-60 cell panel. By correlating the mRNA expression pattern of the SLCO and SLC22 family member gene products with the growth-inhibitory profiles of 1,429 anticancer drugs and drug candidate compounds tested on the NCI-60 cell lines, we identified SLC proteins that are likely to play a dominant role in drug sensitivity. To substantiate some of the SLC-drug pairs for which the SLC member was predicted to be sensitizing, follow-up experiments were performed using engineered and characterized cell lines overexpressing SLC22A4 (OCTN1). As predicted by the statistical correlations, expression of SLC22A4 resulted in increased cellular uptake and heightened sensitivity to mitoxantrone and doxorubicin. Our results indicate that the gene expression database can be used to identify SLCO and SLC22 family members that confer sensitivity to cancer cells.

The role of cellular accumulation in determining sensitivity to platinum-based chemotherapy.

The platinum (Pt) drugs cisplatin and carboplatin are heavily employed in chemotherapy regimens; however, similar to other classes of drugs, a number of intrinsic and acquired resistance mechanisms hamper their effectiveness. The method by which Pt drugs enter cells has traditionally been attributed to simple passive diffusion. However, recent evidence suggests a number of active uptake and efflux mechanisms are at play, and altered regulation of these transporters is responsible for the reduced accumulation of drug in resistant cells. This review suggests a model that helps reconcile the disparate literature by describing multiple pathways for Pt-containing drugs into and out of the cell.

Characterization of the organic cation transporter SLC22A16: a doxorubicin importer.

Specific efflux transporters, such as P-glycoprotein, have been shown to confer drug resistance by decreasing the intracellular accumulation of anticancer drugs. Understanding influx transporters, as well as efflux transporters, is essential to overcome this resistance. We report the expression profile and pharmacological characterization of an organic cation transporter, SLC22A16. The results of our experiments indicate that SLC22A16 is a mediator of doxorubicin uptake in cancer cells. Quantitative real-time RT-PCR analyses show that SLC22A16 is expressed in primary samples taken from patients with acute leukemia. Xenopus oocytes injected with SLC22A16 cRNA import doxorubicin, a widely used anticancer drug for hematological malignancies, in a saturable and dose-dependent manner. The apparent Km value for doxorubicin import was 5.2+/-0.4 microM. In cytotoxic assays, stable transfectants of leukemic Jurkat cells overexpressing SLC22A16 cells became significantly more sensitive to doxorubicin (2 microM) treatment. Characterization of SLC22A16 will help in designing novel therapies targeting hematological malignancies.