c-myc antisense oligodeoxyribonucleotides inhibit proliferation of non-small cell lung cancer.

Background: Mutation or deregulation of certain cellular genes (protooncogenes) results in expression of proteins that appear to promote malignant transformation. Human non-small cell lung cancer has been documented to express many such oncogenes including c-myc, bcl-2, and mutant p53. Antisense oligodeoxyribonucleotides (ASODN) complementary to these oncogenes were tested on three non-small cell lung cancer cell lines for their efficacy in inhibiting cellular proliferation and oncoprotein expression.
Methods: Established non-small cell lung cancer cell lines A427, SKMES-1, and A549 were grown in the presence of ASODNs complementary to messenger RNA of c-myc, bcl-2, p53, or controls at 1 mumol/L or 10 mumol/L concentrations for 4 or 10 days. Cellular proliferation was measured by tritiated thymidine uptake. Flow cytometry was used to quantitate oncoprotein expression. Intranuclear ASODN uptake was documented by fluoresceine-tagged ASODNs.
Results: Fluoresceine-tagged ASODNs were readily taken up by all cell lines. c-myc, as well as bcl-2 and p53 ASODNs, were found to inhibit proliferation of all cell lines significantly compared with controls, most notably in line A549 (40.1% +/- 7.1% of control, p = 0.000 with c-myc ASODN). Antisense c-myc reduced c-myc protein by as much as 71.3% in A427, although protein levels were only minimally reduced in the viable cells of the other lines.
Conclusions: c-myc ASODNs inhibit proliferation of non-small cell lung cancer cell lines as well as reduce c-myc protein expression. Antisense bcl-2 and p53 also cause similar growth inhibition. These results suggest a critical role for activation of these oncogenes in the growth of cultured lung cancer cells. Furthermore, the efficacy and rapid cellular uptake of ASODNs support the potential role of antisense targeting of oncogene expression for pharmacologic control of non-small cell lung cancer.