Circulating tumor cells as a prognostic factor in patients with small cell lung cancer.

The detection of circulating tumor cells (CTCs) in peripheral blood is currently an important field of study. Detection of CTCs by the OBP-401 assay (TelomeScan®) has previously been reported to be useful in the diagnosis, prognosis and evaluation of therapeutic efficacy in breast and gastric cancer. The aim of the present study was to evaluate the OBP-401 assay as a novel method of detecting CTCs of small cell lung cancer (SCLC) patients and to evaluate whether CTC count is associated with prognosis. Prospectively, 30 consecutively diagnosed SCLC patients who had commenced chemotherapy or chemoradiotherapy were enrolled as subjects of the current study. Peripheral blood specimens were collected from the SCLC patients prior to and following the initiation of treatment and the viable CTCs were detected in the specimens following incubation with a telomerase-specific, replication-selective, oncolytic adenoviral agent, which was carrying the green fluorescent protein gene. CTCs were detected in 29 patients (96%). The group of 21 patients with a CTC count of <2 cells/7.5 ml prior to treatment (baseline) had a significantly longer median survival time than the group of eight patients with a CTC count of ≥2 cells/7.5 ml prior to treatment (14.8 and 3.9 months, respectively; P=0.007). The results of a multivariate analysis showed that the baseline CTC count was an independent prognostic factor for survival time (hazard ratio, 3.91; P=0.026). Among the patients that achieved a partial response to treatment, patients who had a CTC count of <2 cells/7.5 ml following two cycles of chemotherapy tended to have a longer median progression-free survival compared with patients who had a CTC count of ≥2 cell/7.5 ml (8.3 and 3.8 months, respectively; P=0.07). Therefore, CTCs may be detected via OBP-401 assay in SCLC patients and the CTC count prior to treatment appears to be a strong prognostic factor.

A novel approach using telomerase-specific replication-selective adenovirus for detection of circulating tumor cells in breast cancer patients.

The aim of this study was to develop a new method for detecting circulating tumor cells (CTCs) in breast cancer patients by using the telomerase-specific replication-selective adenovirus OBP-401. Once transfected, OBP-401 can replicate only in telomerase expressing cells and emit fluorescence as it replicates so that the transfected cells become easily recognizable. Peripheral blood samples were drawn from 50 metastatic breast cancer patients and 27 early breast cancer patients. Blood samples were subjected to both the OBP-401 and CellSearch assays for the detection of CTCs and the results were compared. The recovery rate of the OBP-401 assay was one CTC in 7.5 ml blood combined with high specificity since no CTC was observed in 80 healthy controls. In 50 metastatic patients, 21 patients (42%) were identified as positive with the OBP-401 assay and 27 patients (54%) with the CellSearch assay. The CellSearch assay showed a significantly higher positivity for hormone receptor (HR)-positive tumors (estrogen receptor and/or progesterone receptor-positive tumors) (61%, 25/41, P = 0.012) or CA15-3-positive tumors (69%, 24/35, P = 0.003) than for HR-negative tumors (13%, 1/8) or CA15-3-negative tumors (21%, 3/14), respectively. Contrary, the OBP-401 assay results were similar regardless of their HR status (positive: 44% vs. negative: 38%, P = 0.738) or CA15-3 positivity (positive: 40% vs. negative: 50%, P = 0.523). Of the 27 early stage patients, four patients (15%) were identified by the OBP-401 assay and by the CellSearch assay, respectively, but there was no overlap in the CTCs-positive patients. In conclusion, the OBP-401 assay is comparable to the CellSearch assay in the detection rate of CTCs in both metastatic and early breast cancer patients. However, there was a great discrepancy in patients with CTCs between both assays. The OBP-401 assay may isolate CTCs with other biological characteristics which CTCs detected by the CellSearch assay do not have.

Persistent and stable gene expression by a cytoplasmic RNA replicon based on a noncytopathic variant Sendai virus.

Persistent and stable expression of foreign genes has been achieved in mammalian cells by integrating the genes into the host chromosomes. However, this approach has several shortcomings in practical applications. For example, large scale production of protein pharmaceutics frequently requires laborious amplification of the inserted genes to optimize the gene expression. The random chromosomal insertion of exogenous DNA also results occasionally in malignant transformation of normal tissue cells, raising safety concerns in medical applications. Here we report a novel cytoplasmic RNA replicon capable of expressing installed genes stably without chromosome insertion. This system is based on the RNA genome of a noncytopathic variant Sendai virus strain, Cl.151. We found that this variant virus establishes stable symbiosis with host cells by escaping from retinoic acid-inducible gene I-interferon regulatory factor 3-mediated antiviral machinery. Using a cloned genome cDNA of Sendai virus Cl.151, we developed a recombinant RNA installed with exogenous marker genes that was maintained stably in the cytoplasm as a high copy replicon (about 4 x 10(4) copies/cell) without interfering with normal cellular function. Strong expression of the marker genes persisted for more than 6 months in various types of cultured cells and for at least two months in rat colonic mucosa without any apparent side effects. This stable RNA replicon is a potentially valuable genetic platform for various biological applications.