1991; Elgavish 1991; Coakley et al. 2000)��are actually due to alterations in intracellular pH. The structural integrity and positioning of the Golgi apparatus are dependent on the microtubule cytoskeleton (Thyberg inhibitor Ixazomib and Moskalewski 1993, 1999; Marsh et al. 2001). The distribution of Golgi stacks throughout the cytoplasm of CFPAC-1 cells could result from either a dysfunction in their attachment to microtubules or a change in microtubule distribution. With regard to the first possibility, the greater dispersal and fragmentation of Golgi elements observed in the CFPAC-1 cells treated with nocodazole is an argument in favor of their attachment to microtubules. However, this interpretation will require further experimental investigation.

Regarding the second possibility, we demonstrated by immuncytochemistry an unusual distribution of the microtubule network in CFPAC-1 cells compared with reverted cells. Although in the reverted cells, microtubules extended from a supranuclear region corresponding to the centrosomal region and were also localized along the apico-basal axis, in ��F508 CFPAC-1 cells, microtubules displayed a disorderly distribution and appeared to radiate from different focal points, distributed in a seemingly random fashion. This distinctive microtubule distribution suggested the existence of several nucleation sites. To test this hypothesis, we detected MTOCs using antibodies directed against ��-tubulin. Although most cells in the reverted line contained one or two MTOCs, 63% of the CFPAC-1 cells exhibited an abnormally large number of MTOCs, suggesting the presence of supernumerary centrosomes.

A multiplicity of centrosomes often appears in cancerous cells and is associated with multipolar mitoses (Sato et al. 2001; Gisselsson et al. 2002). In the present study, the number of multipolar mitoses in CFPAC-1 cells was not significantly different from that in the reverted cells and cannot, therefore, explain the abnormally elevated number of MTOCs. The causes of the multiplicity of MTOCs in CFPAC-1 cells and their nature, whether they are centrosomes or other types of MTOCs, like those described in polarized epithelial cells (Meads and Schroer 1995), remain to be determined. A variety of data, however, suggesting that the Golgi complex plays a role in nucleation and the attachment of microtubules, could shed light on these two points (Chabin-Brion et al.

2001). These authors demonstrated the association of a cytosolic fraction of ��-tubulin with Golgi membranes and their capacity to nucleate microtubules. In CFPAC-1 cells, the numerous MTOCs could correspond to non-centrosomal nucleation sites of microtubules associated with Golgi stacks. In this case, the dispersal of the Golgi complex Entinostat would be responsible for the large number of MTOCs and, consequently, the unusual distribution of the microtubule network.