Effects of Tumor Bearing on Serum and Liver Lipid Levels

1INTRODUCTION Tumor cells have a very distinctive metabolism. Several previous studies have considered the metabolic changes that take place in the host after tumor implantation. Metabolic abnormalities arising from malnutrition and malignancy are seen in animals or patients with cancer cachexia. Various cancers affect the lipid metabolism.1-7) Rats subcutaneously implanted with the ascites hepatoma cell line AH109A show hyperlipidemia with a notable decrease in the high-density lipoprotein (HDL) fraction and an enormous increase in the very-lowdensity lipoprotein (VLDL) plus low-density lipoprotein (LDL) fractions5-7) during growth of the solid tumor.5) AH109A is a hepatoma and originates from the liver. Major lipid metabolism occurs in the liver; this includes cholesterol, fatty acid, and triglyceride biosyntheses as well as VLDL production. It is therefore believed that hepatoma cells may affect the lipid metabolism in the host body and that the cancer state affects the lipid metabolism. Sato lung carcinoma (SLC) is a transplantable solid pulmonary tumor induced in a male Donryu strain rat with 4-nitroquinoline 1-oxide. SLC cells injected intravenously have been found to produce metastatic foci only in the lung, with all injected rats dying of pulmonary metastases.8,9) In the present study, to investigate the effects of the SLC implantation on lipid metabolism, changes in lipid levels in the serum and liver were examined in SLC-implanted rats. A previous study reported that SLCbearing rats implanted with 5×106 cells showed a decrease in the serum HDLand esterified cholesterol concentrations. The solid tumor was observed within a short time after SLC implantation, although the solid tumor stopped growing and the solid tumor weight was less than 1% of the body weight on the 21st day after SLC implantation.10) Therefore, in the present study, rats were implanted with 5×107 SLC cells or 5×106 SLC cells to investigate the effects of the number of tumor cells implanted on serum and liver lipid levels.