An N-terminal truncated carboxypeptidase E splice isoform induces tumor growth and is a biomarker for predicting future metastasis in human cancers
Terence K. Lee, … , Ronnie T. Poon, Y. Peng Loh
Terence K. Lee, … , Ronnie T. Poon, Y. Peng Loh
Published February 1, 2011
Citation Information: J Clin Invest. 2011;121(3):880-892. https://doi.org/10.1172/JCI40433.
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Research Article Oncology

An N-terminal truncated carboxypeptidase E splice isoform induces tumor growth and is a biomarker for predicting future metastasis in human cancers

Abstract

Metastasis is a major cause of mortality in cancer patients. However, the mechanisms governing the metastatic process remain elusive, and few accurate biomarkers exist for predicting whether metastasis will occur, something that would be invaluable for guiding therapy. We report here that the carboxypeptidase E gene (CPE) is alternatively spliced in human tumors to yield an N-terminal truncated protein (CPE-ΔN) that drives metastasis. mRNA encoding CPE-ΔN was found to be elevated in human metastatic colon, breast, and hepatocellular carcinoma (HCC) cell lines. In HCC cells, cytosolic CPE-ΔN was translocated to the nucleus and interacted with histone deacetylase 1/2 to upregulate expression of the gene encoding neural precursor cell expressed, developmentally downregulated gene 9 (Nedd9) — which has been shown to promote melanoma metastasis. Nedd9 upregulation resulted in enhanced in vitro proliferation and invasion. Quantification of mRNA encoding CPE-ΔN in HCC patient samples predicted intrahepatic metastasis with high sensitivity and specificity, independent of cancer stage. Similarly, high CPE-ΔN mRNA copy numbers in resected pheochromocytomas/paragangliomas (PHEOs/PGLs), rare neuroendocrine tumors, accurately predicted future metastasis or recurrence. Thus, CPE-ΔN induces tumor metastasis and should be investigated as a potentially powerful biomarker for predicting future metastasis and recurrence in HCC and PHEO/PGL patients.

Authors

Terence K. Lee, Saravana R.K. Murthy, Niamh X. Cawley, Savita Dhanvantari, Stephen M. Hewitt, Hong Lou, Tracy Lau, Stephanie Ma, Thanh Huynh, Robert A. Wesley, Irene O. Ng, Karel Pacak, Ronnie T. Poon, Y. Peng Loh

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Figure 1

Schematic and characterization of ΔN-splice variant of CPE in HCC cells.

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Schematic and characterization of ΔN-splice variant of CPE in HCC cells....
(A) Diagram showing human WT and human ΔN-splice variant CPE-ΔN mRNA and protein derived from bioinformatic analysis (see Methods). (B) Semiquantitative PCR showing the 148-bp predicted product of CPE-ΔN and 18S RNA in high (H) and low (L) metastatic MHCC97 cells after 31 cycles of co-amplification. (C) Northern blot showing the CPE-ΔN transcript of approximately 2.4 kb in MHCC97H cells. (D) Western blot showing the endogenous ΔN-splice variant CPE-ΔN product in MHCC97H cells. The identity of the approximately 40-kDa band as hCPE-ΔN isoform was verified by immunostaining with both a mouse monoclonal CPE antibody and a rabbit polyclonal antibody (no. 6135) generated against a CPE peptide (mouse pre-pro-CPE amino acids 362–379) in our laboratory. Furthermore, absorption control with the antigenic peptide abolished this approximately 40-kDa band. The left lane was run on a separate blot; the right two lanes were run on the same blot but were noncontiguous.