The percentage of cells capable of forming spheres, termed the "sphere formation efficiency" (SFE), was calculated as follows: [(number of spheres formed/number of single cells plated) × 100].
Based on their relative paucity in the pancreas, it is unlikely that centroacinar cells are the exclusive source of spheres within this CD133+ fraction, as more than 11% of CD133+ cells were capable of generating spheres.
Second, it diminishes the culture of cells lacking drug efflux ability but capable of forming spheres.
All three shER clones were capable of forming spheres at sizes and frequencies similar to those of control MCF7S cells (not shown), confirming that ERα was not required for tumorsphere formation or maintenance.
LA-N-5 tumorsphere forming efficiency appeared steady regardless of plating density, with 30 40% of cells capable of forming spheres when plated at 100 or 10 cells per well, and 30% of wells receiving a single cell showing clonally derived spheres (Fig. 1D).
CD44+CD54+ cells were more capable of forming spheres than populations with other surface marker combinations.
Three cell lines, PANC-1, PSN-1 and CFPAC-1, were capable of forming spheres.
We found that all MPM cell lines are capable of producing spheres for three consecutive generations thus sustaining the property of self-renewal, a stem cell feature considered as a key discriminating difference between CSCs and non-CSCs [ 27].
By day 15, the single cells derived from the spheres had formed small clusters, and a typical sphere appeared after ∼30 days (Fig. 3C); approximately 0.2% of the cells from a single dissociated sphere were capable of forming new spheres.
Moreover, we have shown that these cells display high proliferation rate and that they are capable of forming cluster spheres.
