Estimation of glycogen levels in human colorectal cancer tissue: relationship with cell cycle and tumor outgrowth

In this study, we quantitatively measured glycogen levels in tissue samples obtained from tumors, regions adjacent to tumor, and regions of normal colorectum to determine whether the levels were related to cell cycle and cancer growth. Glycogen levels were analyzed in relation to histopathological factors, (tumor size and stage of disease) and cell cycle progression. The glycogen level was found to be highest in the cancer tissue, lower in normal tissue, and lowest in the adjacent tissue. The difference in glycogen level between the cancer tissue and the other two regions was significant (P < 0.05). There was a negative correlation between glycogen level and tumor size, but it was not significant. The level of glycogen in cancer tissues decreased as the stage of the disease progressed, but a significant difference was not found between stages. There was a negative correlation between the glycogen level and the proliferation index. There was a positive correlation between the glycogen level and the proportion of cancer cells in G(1) phase, while there was a negative correlation with S and G(2)M phases. Glycogen levels were highest in cancers with a high proportion of cells in G(1), and decreased with progression to S phase. It may be that glycogen is utilized in the progression to S phase, and the cancer tissues are supplied with glycogen from the tumors themselves as well as their adjacent tissues. Cancer growth may be inhibited by artificial control of the glycogen level in the G(1) phase of cancer cells.