Tumor response to radiotherapy is dependent on genotype-associated mechanisms in vitro and in vivo

Table 1 Genetic variation and in vitro radiosensitivity of eight human tumor cell lines.

Radio-Sensitivity Group*	Cell Line	Genetic Characteristics			In Vitro Radiosensitivity
		TP53	p21 induced	MMR
VR	U251	mt (273arg-his)	-	+	Most resistant cell line, other radioresistant glioblastomas segregate into this group.
R	DLD1	mt (241ser-phe)	-	hMSH6-	Other epithelial tumors that express mutTP53 segregate into this group.
	19S186	p21 double knockout from DLD1
S	HCT116	wt	+	hMLH1-	Other epithelial tumors that express wtTP53 segregate into this group.
	379.2	p53 double knockout from HCT116.
	80S4	p21 double knockout from HCT116
	14-3-3σ-/-	14-3-3σ double knockout from HCT116
VS	SW1222	null	-	+	Most sensitive cell line, mutant in the ATM gene with an A moiety inserted in codon 6997 of exon 50.

As defined in Williams et al. [2].
Cell lines fall into four radiosensitivity groups as defined by Williams et al. 2007, 2008a. All cell lines were derived from human colorectal tumors except U251 that is derived from a human glioblastoma. Expression of TP53 and radiation induced p21 were assayed by Western blot analysis. Deficiency in MMR (DNA mismatch repair) is a marker that these tumor developed in individuals expressing HNPCC (human non-polyposis colorectal cancer).