Screening and identification of peritoneal metastasis-related genes of gastric adenocarcinoma using a cDNA microarray

With the aim of identifying peritoneal metastasis-related genes in gastric cancer, we performed a broad analysis of differential gene expression between the parental cell line GC9811 and its highly metastatic peritoneal counterpart, cell line GC9811-P. Two fluorescent cDNA probes, labeled with Cy3 and Cy5 dyes, were prepared from GC9811 and GC9811-P mRNA samples by the reverse transcription method. The two color probes were then mixed and hybridized to a cDNA chip constructed with double-dots from 11,901 human genes; this was scanned at two wavelengths. The experiment was repeated twice. In GC9811-P cells, 218 genes were upregulated and 30 genes were downregulated compared with the parental cell lines. Some selected genes were confirmed by RT-PCR and Western blot; we found that S100A4 and CTNNB1 were upregulated and PTEN was downregulated in GC9811-P cells. Identification of these differentially expressed genes could contribute to disclose the molecular mechanisms involved and provide new targets for therapeutic intervention to avoid peritoneal dissemination of gastric adenocarcinoma.

SU-E-T-104: Commissioning and Dosimetric Characteristics of TrueBeam System: Composite Data of Three TrueBeam Machines

INTRODUCTION

A TrueBeam linear accelerator (TB-LINAC) is designed to deliver standard flattened and flattening-filter-free (FFF) beams. In our institute, three TB-LINAC units are installed. In this work, composite data of the three units and multi-unit comparison are presented.

METHODS

Each TB-LINAC can deliver photon beams from 4MV to 15MV, electron beams from 6MeV to 22MeV, and 6MV-FFF and 10MV-FFF. Dosimetric characteristics are systematically measured for commissioning including percent depth dose (PDD), beam profile, relative scatter factor, dynamic leaf shift, output factor and MLC leakage. Critic considerations of Pion of FFF photon beams and dosimetric penumbra are investigated.

RESULTS

All measured PDDs and profiles of photon and electron matched well across the three machines. Beam data were quantitatively compared and combined through average to yield composite beam data. The discrepancies among the machines were quantified using standard deviation (SD). For example, the mean SD of the PDDs among the three units is 0.12%, and the mean SD of the profiles is 0.40% for 10MV-FFF open fields. The variations of Pion of the chamber CC13 is 1.2±0.1% under 6MV-FFF and 2.0±0.5% from dmax to the 18cm-off-axis point at 35cm depth under 40×40cm² . The measured relative output factors range from 0.866 to 1.141 with the mean discrepancy of 0.06±0.04% among the three units. The measured wedge factors range from 0.863 to 1.254 with the mean overall discrepancy of 0.04±0.04%. The mean MLC transmission and dynamic leaf shift were measured from 1.0% to 1.5% and from 0.77mm to 0.96 mm from 4MV to 15MV. The mean penumbra of various photon beams are measured from 5.88±0.09mm to 5.99±0.13mm from 4MV to 15MV at 10cm depth of 10×10 cm² .

CONCLUSIONS

Dosimetric data demonstrated that the three units could and had been matched well. The systematically measured data might be useful for future reference.