ATYPICAL MICROTUBULE ORGANIZATION IN UNDIFFERENTIATED HUMAN COLON-CANCER CELLS

We previously reported that undifferentiated colonic cancer HT-29 cell s, unlike the differentiated ones, exhibit unusual organelle distribut ions and atypical vesicle trafficking patterns, which are microtubule- independent and microfilament-dependent. In the present study, we have analyzed the microtubule network in both phenotypes, using confocal m icroscopy, and determined the expression levels of some microtubule-as sociated proteins by quantitative immunoblotting. Differentiated cells exhibited the microtubular organization of polarized epithelial cells . Non-polarized undifferentiated cells presented an atypical microtubu le organization as microtubules were localized mainly at the cell 'top '. Immunoblot analysis indicated the absence or low content of several structural and motor microtubule-associated proteins in undifferentia ted cells, compared to differentiated cells. This may explain in part their atypical microtubular organization. This study agrees with a cru cial role for microfilaments in the intracellular organization of undi fferentiated HT-29 cancer cells, while differentiated HT-29 cells exhi bit intracellular organization similar to that of normal enterocytic c ells, although they are also tumoral. ((C) Academie des sciences/Elsev ier, Paris.).