Histological and thermodynamical features of cathepsin B-positive tumors of non-small cell lung cancer obtained by syntactic structure analysis

Abstract

Cellular orders in normal tissue and in tumors can be described on the basis of physical terms. Assuming that the peptidase cathepsin B is involved as an essential factor in tumor progression we analyzed the corresponding distribution pattern and determined the entropy of this cell fraction in tumors by syntactic structure analysis using nearest neighbor relationships. Of the 120 surveyed sections from primary lung tumors 62 (51.7 %) were identified with cathepsin B expressing cells. Cathepsin B-positive tumor cells have significantly shorter mean cell-cell distances (p<0.01) and form significantly higher number of tumor cell clusters (p<0.01) when compared with cathepsin B-negative tumor cells. The diameters of the cathepsin B positive tumor cell clusters are increased in moderately and intensively stained tumor cell areas compared to the cathepsin B negative ones (p<0.1 and p<0.05, respectively). The mean cell-cell distance between positive tumor cells was significantly shorter in squamous cell carcinomas (SCC) compared to adenocarcinomas (AC) (p<0.01). We found an increased number of tumor cell clusters in intensively stained areas of SCC compared with AC (p<0.05). Interestingly, in dedifferentiated tumors cells which strongly expressed cathepsin B, have significantly (p<0.01) shorter mean cell-cell distances compared with those well differentiated tumors. In conclusion, cathepsin B positive tumor cells have shorter mean cell-cell distances and form higher number of tumor cell clusters. Our findings indicate that cathepsin B positive tumor cells of primary lung tumors seem to detach as tumor cell clusters instead of single tumor cells. This process appears to be more pronounced in squamous cell carcinomas than in adenocarcinomas.