Table 1. Clinicopathological parameters and human MDM2 SNP309 genotypes in the unselected cohort of RCC patients.

Clinicopathological parameters	No. of patients	SNP309			P-valuea
	Total	T/T	T/G	G/G
Total	197	63	116	18
Gender					0.534
Females	80	22	50	8
Males	117	41	66	10
Morphology					0.453
Clear cell	181	61	103	17
Papillary	10	2	8	0
Chromophobe	5	0	4	1
Unknown	1	0	1	0
Age (years)					0.760
⩽67	101	30	61	10
>67	96	33	55	8
Age (years)
Females	80
⩽68	43	9	27	7	0.077b
>68	37	13	23	1	0.024c
Males	117				0.613
⩽67	62	21	37	4
>67	55	20	29	6
Tumor stage					0.346
pTa	1	0	1	0
pT1	108	32	70	6
pT2	24	7	14	3
pT3	59	22	28	9
pT4	2	0	2	0
Unknown	3	2	1	0
Grouped tumor stage
pTa+pT1+pT2	133	39	85	9	0.082
pT3+pT4	61	22	30	9
unknown	3	2	1	0
Tumor grade					0.855
G1	30	9	19	2
G2	100	29	60	11
G3	62	22	35	5
Unknown	5	3	2	0
Grouped tumor grade
G1+G2	130	38	79	13	0.662
G3	62	22	35	5
Unknown	5	3	2	0

Age groups were separated by the medians (67 years for all RCC patients, 68 years for female RCC patients and 67 years for male RCC patients).

DNA from part of the unselected cohort (n=137) and the age-selected cohort was isolated from kidney specimens of patients who had undergone surgery for RCC. For this purpose, normal kidney tissue of the highest purity possible was needed. Therefore, three experienced uropathologists (AH, SB and VS) marked tumor-free areas on hematoxylin and eosin staining that had been obtained from formalin-fixed and paraffin-embedded tissues. Then, 5 μm sections from the respective specimens were deparaffinized and manually microdissected after 15 s staining by 0.1% methylene blue using the marked hematoxylin and eosin staining as a template. The purity of the obtained tumor-free kidney tissue was near 100%.

DNA from normal kidney tissue (n=137) was isolated using the Maxwell 16 LEV Blood DNA Kit (Promega Corporation Mannheim, Germany) according to the manufacturer's instructions. Furthermore, we isolated DNA from the blood lymphocytes of additional RCC patients of the unselected cohort (n=60) as previously described.²⁷

To genotype the unselected cohort (n=137) and the age-selected cohort (n=205) for MDM2 SNP309, we used a restriction fragment length polymorphism approach as summarized in Hitzenbichler et al.,²⁸ whereby the unselected cohort was analyzed on a 2.5% agarose/TAE gel instead of a capillary sequencing system. In addition, genotyping of the other part of the unselected cohort (n=60) was performed as described previously.⁷

^aCross tables, χ²-test, significant values are in bold face.

^bAll genotypes.

^cGenotypes G/G vs T/T.