A pharmacological analysis of the cholinergic regulation of urokinase-type plasminogen activator secretion in the human colon cancer cell line, HT-29

Preparation and antitumor effect of a toxin-linked conjugate targeting vascular endothelial growth factor receptor and urokinase plasminogen activator

The aberrant signaling activation of vascular endothelial growth factor receptor (VEGFR) and urokinase plasminogen activator (uPA) is a common characteristic of many tumors, including lung cancer. Accordingly, VEGFR and uPA have emerged as attractive targets for tumor. KDR (Flk-1/VEGFR-2), a member of the VEGFR family, has been recognized as an important target for antiangiogenesis in tumor. In this study, a recombinant immunotoxin was produced to specifically target KDR-expressing tumor vascular endothelial cells and uPA-expressing tumor cells and mediate antitumor angiogenesis and antitumor effect. Based on its potent inhibitory effect on protein synthesis, Luffin-beta (Lβ) ribosome-inactivating protein was selected as part of a recombinant fusion protein, a single-chain variable fragment against KDR (KDRscFv)-uPA cleavage site (uPAcs)-Lβ-KDEL (named as KPLK). The KDRscFv-uPAcs-Lβ-KDEL (KPLK) contained a single-chain variable fragment (scFv) against KDR, uPAcs, Lβ, and the retention signal for endoplasmic reticulum proteins KDEL (Lys-Asp-Glu-Leu). The KPLK-expressing vector was expressed in Escherichia coli, and the KPLK protein was isolated with nickel affinity chromatography and gel filtration chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis test demonstrated KPLK was effectively expressed. Result of in vitro cell viability assay on non-small cell lung cancer (NSCLC) H460 cell line (uPA-positive cell) revealed that KPLK significantly inhibited cell proliferation, induced apoptosis, and accumulated cells in S and G2/M phases, but the normal cell line (human submandibular gland cell) was unaffected. These effects were enhanced when uPA was added to digest KPLK to release Lβ. For in vivo assay of KPLK, subcutaneous xenograft tumor model of nude mice were established with H460 cells. Growth of solid tumors was significantly inhibited in animals treated with KPLK up to 21 days, tumor weights were decreased, and the expression of angiogenesis marker CD31 was downregulated; meanwhile, the apoptosis-related protein casspase-3 was upregulated. These results suggested that the recombinant KPLK may have therapeutic applications on tumors, especially uPA-overexpressing ones.

Is acetylcholine a signaling molecule for human colon cancer progression?

OBJECTIVE

Non-neuronal acetylcholine (ACh) has been suggested to be a mediator for the development of various types of cancer. We analyzed a possible role for this molecule in carcinogenesis and/or progression of human colon cancer, in patient biopsies harvested from the colon during surgery. We addressed whether ACh synthesis (by choline acetyltransferase) and/or degradation (by ACh esterase), as well as the expression of the α7-subtype of the nicotinic ACh receptors, and the peptide ligand at the α7 receptors, secreted mammalian Ly6/urokinase-type plasminogen activator receptor-related protein-1, respectively, are deranged in tumor tissue as compared with macroscopically tumor-free colon tissue.

METHODS

A total of 38 patients were grouped for analysis based on their respective Dukes stage (either Dukes A + B or C + D). A mucosal tissue sample was harvested from macroscopically tumor-free colon tissue (i.e. control tissue), as well as from the tumor, and protein lysates were prepared for quantitative Western blotting. Full-thickness specimens were taken for immunohistochemistry.

RESULTS

For all the above named markers, there was a significant difference between control and tumor tissue with regard to protein levels, and there was, in addition, a significant difference in protein levels between the Dukes A + B and C + D groups.

CONCLUSION

The current findings may suggest a role for ACh in colon carcinogenesis/cancer progression; the data obtained could have prognostic and/or therapeutic significance for this disease.