A cDNA molecule that encodes a protein designated Labyrinthin (Lab) is isolated and its nucleotide sequence is determined. The protein, or peptides derived from the protein, are markers useful to define novel classes of cancers. Diagnostic assays for these cancers use antibodies to Lab or nucleotide probes that hybridize with the lab gene or a fragment therefrom. Vaccines useful either to prevent recurrence of cancers in subjects who test positive for Lab (or lab), or to prevent initial occurrence of cancer, use proteins or peptides derived from Lab. Expression of Lab via immunogenic assays is used to monitor effects of cancer treatments. Antisense molecules against lab are used in treatments. Sense molecules of lab are used to restore lost lab function in diseased normal cells, for example, gland cells.