Cells were considered at population doubling zero at the first time they are exposed to cancer
cell line condition medium or patient serum-added culture medium. At every passage, cell
number was determined and population doubling was calculated using the following formula;
PDL = log(Nh/Ni) / log2, where Nh is the number of cells harvested at the end of the
incubation time and Ni is the number of cells inoculated at the beginning of the incubation
time. Cumulative PDL was calculated by adding the previous calculated PDL.