cells.TPA concentration was 1.6×10-8 mol/L
The nuclear features were measured on microphotographs using a commercially available software. Table 2 summarizes the results. TPA might decrease the cells size but no significant difference with the control group.
Table 2 Measurements of nuclei morphometry after TPA treatments (x±s)
3 Discussion
Our results show that Eca109 human esophageal cancer cell is a cell type which does not respond to exposure to TPA by growth arrest (Table 1 and Fig.1). A marked change in cell morphology was not observed. On comparison of the different human cell systems in which phorbol esters cause growth arrest，the behavior of the Eca109 cells appears to resemble that of SMMC7221 human hapatoma cells［6］ and HT29 human colon cancer cells［8］. Even in T cell leukemia TPA could induce Jurkat and Molt3 cells to differentiate but could not induce CCRF-CEM and CCRF-HSB2 cells to differentiate. The reasons are not known.
Morphometric analysis has been used successfully as a diagnostic and prognostic criterion in patients with malignancies［9］.Many investigators have sought an accurate and reproducible parameter that will allow accurate prediction of adjunctive immunotherapy or chemotherapy when appropriate［10］.These morphometric studies have provided valuable information. We used quantitative morphometry to investigate the shape difference of neoplastic nuclei from esophageal cancer cells with or without treatment of TPA. TPA did not clearly change the shape of the cells nuclei，but it did change other cells’ nuclei which were found in our laboratory (data not shown). This result is possibly consistent with that of TPA on cells proliferation. When TPA induces tumor cells to differentiation，it has antiproliferation function. If tumor cells proliferate actively，differentiation may stop at least temporarily. The reasons that TPA did not influence the proliferation and nuclear morphometry of esophageal cancer cells are possibly connected to the diversity and cellular distributions of protein kinase C (PKC) on the cells. Protein kinase C (PKC) is a family of phospholipid-dependent serine-threonine kinases that play important roles in the signal transduction and in the regulation of cell growth and differentiation［11］.At least eleven isoforms of PKC have been isolated so far，showing diversity in their structures，cellular distributions，and biological functions［12］.PKC is also the receptor for the potent tumor-promoting phorbol esters，which can substitute for DAG in PKC activation. Reports also showed that different PKC subtype was involved in the differentiation of different tumor cells during TPA treatments［13］. Therefore，the distributions and the activity of PKC in Eca109 cells might be different with other tumor cells and have different signal transduction systems. So TPA might have different effects on different tumor cells. Further studies about the distributions and active status of PKC subtypes on human esophageal cancer cells may not only provide useful information on selection effective differentiation-inducers but also contribute to elucidation of the molecular mechanism involved in their differentiation and tumorigenicity.
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