Searching for T cells that had infiltrated the tumors, they collected as many as 50 T cell samples from a single tumor; next, the team tested each batch of T cells against other tumor samples from the same patient.
Such a high proportion of expressed genes may be at least in part explained by the presence of many cell types in our samples [ 15- 17].
We find that this RAS pathway signature is a high sensitivity but low specificity predictor of KRAS mutation status, as many cell line and tumor samples appear to have RAS pathway activation in the absence of mutations in KRAS.
A recent analysis of many cell lines and clinical samples from breast, prostate and other tumours has indicated that they contain a small fraction of cells identified by a variety of cell surface markers, expression of stem cell genes, reconstitution of tumours in vivo and enhanced drug resistance (Sales et al, 2007).
Even when focusing on one single technique and one well-defined cell type, measured cell stiffness seems to inherently display a very broad, non-Gaussian spread [ 260] (some approach this problem by averaging over many cells using larger samples [ 277]). Figure 21 shows typical measurement curves for a selection of four different methods.
Although PECAM-1 stained many cells inside the samples, similarly to CD68, this was also identified around large blood vessels in the abdominal fascia at day 3; while, after 7 days of implantation, new small blood vessels inside all samples were stained.
Two types of positive staining were evident: scattered positive cells within a predominantly negative sample (5/20), or diffuse staining across many cells in the sample (3/20).
In order to calculate how many cells within a sample are needed to minimally repopulate a mouse (a repopulating unit) small numbers of cells (5000, 1000, or 400) were injected into sub-lethally irradiated NSG mice.
In addition, it offers the convenience and simplicity for sampling many cells in solution without requiring extensive sample preparation, such as the need to modify surfaces to promote cell adhesion.
