Human nasopharyngeal carcinoma (NPC) cell line, CNE-2Z, and its clones (L₂, H₂, L₄) with various invasive and metastatic potentials were examined for their gap junctions (GJ), gap junctional intercellular communication (GJIC) and the concentration of cytosolic free calcium ([Ca²⁺]_i). Only a few intermediate junction (IJ) but no GJ structures were observed under electron microscope (EM). CNE-2Z cells showed marked JGIC, while its variants lacked this function using the scrapeloading dye-transfer technique (SLDT). There was lower concentration of [Ca²⁺]_i in L₂ cells (a variant with high invasive and metastatic potential) compared to that in H₂ and L₄ cells (variants with medium and low invasive and metastatic potentials, respectively). These data suggested that high invasive and metastatic potentials might be correlated with the level of [Ca²⁺]_i in NPC cells.



The effect of RII (4-hydroxycarbophenyl retinamide) on NPC cells also investigated,. After 3-7 d of RII (10^-5M) treatment, there was no change in the number of gap junctions and other kind of intercellular junctions in NPC cells observed under EM. The JGIC of CNE-2Z weaked and then disappeared finally with prolonging of RII treatment. However, there was no influence on its variants. The level of [Ca²⁺]_i in NPC cells apparently fell after 6 h of RII treatment, and rose to original level with persisting of RII treatment. Whether the fluctuating of [Ca²⁺]_i level is related to the inhibitory effect of RII treatment on growth and invasion of NPC cells needs to be further studied.