Experimental gene therapy of human colon

Background. Gastrin regulates growth of human colon cancer cells by activation of the cyclic adenosine monoPhosphate (cAMP) -dependent protein kinase A (PKA). Gastrin and 8-Br-cAMP, a membrane-permeable cAMP analag, inhibit growth of HCT116 cells,' both stimulate growth of LoVo cells. This dualeffecton growth may be explained by relative amounts of the regulatory subunit (Rla or RIIP) of PKA within the cancer cells. Antisenseoligodeoxynucleotides (ASO) to either R1a or RIIP inhibit protein translation of the target mRNA by sequence-specific binding,. subsequently, cellular PKA content and the cAMP-mediated growth may be altered. We determined whether ASO to either the Rla or RIIP subunit altered the cAMP-mediated growth of HCT116 and LoVo human colon cancer cells. Methods. HCT116 cells were treated with RIIP ASO (15 JLmol/L, 4 days) and then treated with 8-Br-cAMP (25 JLmol/L),' tritiated thymidine incorporation was measured after 24 hours, and the cell number was determined on alternate days. Protein and mRN A levels of the RIIP subunit were determined by Western and Northern blotting, respectively. Similar studies with an ASO against the R1a subunitwere performed on Lo Vo cells. Results. RIIP ASO reversed the cAMP-mediated inhibition of growth of HCT116 cells, and RIIP ASO decreased the protein level of the RIIP subunit. RIIP ASO did not alter the basal growth of HCT116 cells. Rla ASO reversed the cAMP-mediated stimulation of growth of LoVo cells. Conclusions. The regulatory subunits of PKA are potential targets to alter growth of human colon cancer cells. Gene therapy directed to alter speclflc steps in signal transduction pathways may provide new therapeutic strategies. (SURGERY 1994,'116:189-96.)