c-myc amplification and enhancement of sensitivity to cytosine arabinoside: An in vitro and in vivo study on four sublines established from a pulmonary adenocarcinoma

Purpose. Meticulous treatment strategies taking tumor heterogeneity into account are considered essential to achieve breakthroughs in current cancer therapy. We analyzed tumor heterogeneity in the primary tumor of a patient with pulmonary adenocarcinoma characterized by a poor prognosis. Methods. Four sublines with different growth characteristics in vitro were established from the tumor using a method for short-term selective cultivation. We examined the differences in morphological, biochemical, and genetic findings of these sublines. Results. Differences in the histological features of the transplanted tumors were seen in the four sublines. The 88-2T and 88-2 tumors revealed a well-differentiated adenocarcinoma; the 88-2F tumor revealed a large cell-like carcinoma resembling the metastatic tumor in the lymph nodes; and the 88-2FA tumor was composed of signet-ring cells. There were differences in oncogenes, with the 88-2F line alone exhibiting 12-fold amplification of c-myc. Sensitivity to cytosine arabinoside (Ara C) was specifically increased in the 88-2F cell line, alone. Conclusions. These sublines demonstrate that human pulmonary adenocarcinoma has various types of heterogeneity within the primary tumor. Furthermore, c-myc amplification may play an important role in altering phenotype and growth characteristics in vitro and in vivo, and for increasing sensitivity to Ara C and the potential of cancer cells to metastasize to lymph nodes.