Immunoglobulin kappa and immunoglobulin lambda are required for expression of the anti-apoptotic molecule Bcl-xL in human colorectal cancer tissue

Abstract

Objective. Aberrant expression of immunoglobulin (Ig) by cancer cells has been documented in a number of malignant tumors but its biological significance is unclear. Cancer cells overexpress anti-apoptotic molecules such as Bcl-xL. The present study aimed to examine the role of expression of Ig light-chain Igĸ and Igλ in maintaining the high levels of Bcl-xL in colorectal cancer cells. Material and methods. Thirty patients with colorectal cancer were recruited to this study. Expression of Igĸ, Igλ and Bcl-xL in surgically removed cancer tissue was examined by immunohistochemistry and/or flow cytometry. Using the HT29 cell line as a study platform, RNA interference (RNAi) was employed to knock out the genes of Igĸ and Igλ in the cancer cell line; the expression of Bcl-xL in HT29 cells was subsequently analyzed. Results. Human colorectal cancer cells, but not normal colorectal tissue, expressed both Igĸ and Igλ in the cytoplasm. High levels of Bcl-xL were detected in cancer cells. Using RNAi to knock out the genes of Igĸ and/or Igλ, Bcl-xL expression in HT29 cells was significantly suppressed and the cells became apoptotic. Conclusion. The results suggest that expression of Igĸ and Igλ is required to stabilize Bcl-xL expression in cancer cells.

Key Words::

• Apoptosis
• cancer
• colon
• immunoglobulin
• RNA interference

Acknowledgements

This study was supported by grants from the Canadian Institute of Health Research (CIHR). P.-C. Y. holds a New Investigator Award from CIHR. The authors report no conflicts of interest.