A pH-dependent charge reversal peptide for cancer targeting.

Naturally occurring cationic antimicrobial peptides exhibit not only antimicrobial activity, but also anticancer activity and are expected to be new weapons in cancer treatment. The selectivity for cancer cells over normal cells is at least partly due to the more negative surface of cancer cells. A lower pH in tumor tissue (pH 6.2-6.9) than that in normal tissues (pH 7.3-7.4) has also been utilized to develop anticancer agents. However, cytotoxicity against normal cells at physiological pH is often an issue. Furthermore, acidic regions can be found in some normal tissues such as the kidneys. Therefore, existing approaches to cancer targeting are not fully satisfactory. In this study, we designed a peptide, HE (GIHHWLHSAHEFGEHFVHHIMNS-amide), with a charge that reverses from -1.5 at pH 7.4 to +6 at pH 5.5 for cancer targeting at low pH based on the antimicrobial peptide magainin 2 by introducing 6 His, an additional Glu, and an amidated terminal. HE interacted with cancer-mimicking negatively charged liposomes in a pH-dependent fashion with a midpoint with a pH of 6.5 just above the membrane surface. The peptide killed human renal adenocarcinoma ACHN cells at pH 6.0, but not at pH 7.4, and was nontoxic against human normal glomerular mesangial cells even at this low pH. Thus, the novel peptide may be a promising lead peptide for cancer therapy, although this derivatization resulted in weakened cytotoxicity.

Mutations and aberrant transcriptions of Stk11 (Lkb1) gene in rat liver tumors.

UNLABELLED: To clarify the involvement of the Stk11/Lkb1 gene in the development of hepatocellular carcinomas (HCCs), its alteration in rat HCCs induced by exogenous and endogenous liver carcinogenesis models was investigated. MATERIALS AND METHODS: Fifteen HCCs induced by N-nitrosodiethylamine (DEN) and 12 HCCs induced by a choline-deficient L-amino acid-defined (CDAA) diet were obtained. To assess mutations and aberrant transcriptions of the Stk11 gene, polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) and reverse transcription (RT)-PCR analyses were performed, respectively. RESULTS: A mutation was detected in only 1 out of 15 HCCs by DEN, but no mutations in 12 HCCs by the CDAA diet. Aberrant transcripts were found in 4 out of 15 HCCs by DEN and in 3 out of 12 HCCs by the CDAA diet. CONCLUSION: These results suggest that alterations of the Stk11 gene may play a limited role in both exogenous and endogenous rat liver carcinogenesis.

Alterations of the LKB1 gene in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine in rats.

OBJECTIVE: Germ line mutations of the LKB1 gene cause the autosomal dominant Peutz-Jeghers syndrome (PJS), and PJS has also been associated with an increased risk of developing cancers, suggesting LKB1 may act as a tumor suppressor in PJS. By contrast, LKB1 mutations are rare events in most sporadic tumors in non-PJS patients, except for lung cancers. To better understand the involvement of LKB1 gene alterations during lung carcinogenesis, we investigated the LKB1 gene mutations and expressions in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine (BHP) in rats. METHODS: Male Wistar rats, 6 weeks old, were given 2,000 ppm BHP in their drinking water for 12 weeks and maintained without further treatment until they were sacrificed at 25 weeks. A total of 15 lung adenocarcinomas were obtained, and genomic DNA was extracted for the search of mutations using polymerase chain reaction (PCR)-single strand conformation polymorphism analysis. To assess altered expressions of the LKB1 gene, reverse transcription-PCR analysis was also performed. RESULTS: No mutations were found throughout exons 1-9 in any of the tumors. Aberrant transcripts bearing deletions of nucleotides 216-1459, 289-1302, 268-1261, or 257-1378 were detected in 5 of 15 adenocarcinomas (33.3%). CONCLUSION: These results suggest that alterations of the LKB1 gene might be involved in the development of lung adenocarcinomas induced by BHP in rats.

Different expressions and DNA methylation patterns of lysophosphatidic acid receptor genes in mouse tumor cells.

OBJECTIVE: Lysophosphatidic acid (LPA) receptors act as several biological effectors through LPA, which is a bioactive phospholipid. Recently, aberrant expressions of LPA receptor genes due to DNA methylation have been detected in several tumor cells. In this study, we measured expression levels and DNA methylation status of LPA receptor genes in mouse tumor cells, LL/2 lung carcinoma, B16F0 melanoma, FM3A mammary carcinoma and L1210 leukemia cells, compared with normal tissues. METHODS: Total RNAs were extracted and RT-PCR analysis was performed. For DNA methylation status, bisulfite sequencing analysis was carried out, comparing outcomes with other tumor cells and normal tissues. RESULTS: The expressions of LPA1 gene were shown in LL/2, but not in B16F0, FM3A and L1210 cells. While the LPA2 gene was expressed in all 4 tumor cells, the LPA3 gene was unexpressed in them. The LPA1 and LPA3 unexpressed cells were highly methylated, although normal tissues were all unmethylated. The DNA methylation status was correlated with gene expression levels in cancer cells. CONCLUSION: The present results demonstrate that DNA methylation patterns of LPA receptor genes are dependent on cancer cell types, suggesting that LPA receptors may be new molecular targets for therapeutic approaches and chemoprevention.

No Mutations of Lysophosphatidic Acid Receptor Genes in Lung Adenocarcinomas Induced by N-Nitrosobis(2-hydroxypropyl)amine in Rats.

Lysophosphatidic acid (LPA) is a bioactive phospholipid that stimulates cell proliferation and migration, and protects cells from apoptosis. It interacts with specific G protein-coupled transmembrane receptors. Recently, frequent mutations of the LPA receptor-1 (LPA1) gene were detected in rat lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine (BHP). In this study, to evaluate the involvement of other LPA receptor gene alterations during lung carcinogenesis, we investigated mutations of the LPA2, LPA3, LPA4 and LPA5 genes in lung adenocarcinomas induced by BHP in rats. Fifteen male Wistar rats, 6 weeks of age, were given 2000 ppm BHP in their drinking water for 12 weeks and then maintained without further treatment until sacrifice at 25 weeks, and 15 adenocarcinomas were obtained. Genomic DNAs were extracted from frozen tissues, and the LPA2, LPA3, LPA4 and LPA5 genes were examined for mutations, using polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) analysis. No mutations of LPA2, LPA3, LPA4 and LPA5 were detected in the 15 adenocarcinomas. These results suggest that alterations due to LPA2, LPA3, LPA4 and LPA5 gene mutations might not be involved in the development of lung adenocarcinomas induced by BHP in rats.

Mutations of LKB1 gene in pancreatic ductal adenocarcinomas induced by N-nitrosobis(2-oxopropyl)amine in hamsters.

To evaluate an involvement of LKB1 gene alteration during pancreatic carcinogenesis, mutations in the LKB1 gene in hamster pancreatic duct adenocarcinomas (PDAs) induced by N-nitrosobis(2-oxopropyl)amine (BOP) were investigated. Female Syrian golden hamsters received 30 mg/kg of BOP followed by repeated exposure to an augmentation pressure regimen consisting of a choline-deficient diet combined with DL-ethionine then L-methionine and a further administration of 20 mg/kg BOP. A total of 10 PDAs obtained 10 weeks after beginning the experiment were examined for mutations using reverse transcription (RT)-polymerase chain reaction (PCR)-single-strand conformation polymorphism (SSCP) analysis. Mutations were detected in 3 out of the 10 PDAs (30.0%). Sequence analysis revealed the identity of these mutations to be a CCC to CCT (Pro to Pro) transition at codon 221, a CCG to CAG (Pro to Gln) transversion at codon 324 and a GAC to GGC (Asp to Gly) transition at codon 343. The LKB1 gene may be involved in the development of PDAs induced by BOP in hamsters.