Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to identify the presence of mRNA for NKX2-1, also known as TTF-1, a marker of lung differentiation, and eleven receptor and cytoplasmic tyrosine and serine/threonine kinases, in the BACA and CLAC canine lung cancer lines. The gene discussed is NKX2-1; the disease is lung cancer.