Antigenic epitopes of three tumor-associated antigens of well-differentiated squamous cell carcinoma of the larynx for use in monitoring patients in specific active immunochemotherapy trials.

Laryngeal tumor-associated antigen (LX-TAA-1) monoclonal antibody-derived epitopes were tested by enzyme immunoassay (ELISA) against a coded series of 30 non-laryngeal squamous cancer sera, 32 laryngeal squamous cancer sera and 36 non-squamous cancer sera. Epitope LX-TAA-1 a62 cross-reacted with 46% of non-laryngeal squamous and with 16% non-squamous cancer sera. Epitope i5 cross-reacted with 50% non-laryngeal squamous cancer sera and with 11% non-squamous cancer sera. LX-TAA-1 epitope f18 cross-reacted with 26% of non-laryngeal squamous cancer sera but with only one, at weaker titer, of the non-squamous cancer serums (2%). Preliminary screening had ruled out any reactivity to 92 normal, age- and sex-matched sera. One hundred percent of laryngeal squamous cancer sera showed reactivity to one or more of the three epitopes. These results from highly sensitive testing imply that epitope f18 protein is probably a unique gene product of certain squamous cancer cells in the body. Serial titrations of immunized patient sera indicated that epitope f18 produces a strong but very early reactivity and appears to be a marker for early post-immunization response in patients on immunotherapy, with epitope i5 showing a low but continuing positive response starting at 7 months post-immunization. This is in contrast to our studies in other cancer systems where earlier responses are usual.