Table 1. Frequency of RIS and CIS cluster distance in Mammary HOGs and Mammary tumors.

	HOGs & HOG deriv. Tumors	CzechII	Balb/cf MMTV(CZ)	Balb/cf MMTV(SP)
# of Tumors	127	123	54	85
# of RIS	89	190	150	213
2 cluster distance	305277	46206	46206	46206
3 cluster distance	4317269	653464	653464	653464

The numbers of HOGs and mammary tumors as well as the number of independent RIS per tumor panel is indicated. Identification of CIS or clusters of RIS near a gene was accomplished using the statistical analysis procedure describe by Mikkers et al. [15]. Calculation of CIS clusters was done at the website: [44]. The distance within which 2 or 3 MMTV insertions have to occur for a total of 591 insertions (CzechII, Balb/cfMMTV(CZ) and Balb/cfMMTV(SP)), with a probability of < 0.01 is indicated. This approach led to the identification of 6 CIS and proximal genes in HOGs and HOG derived CzechII mammary tumors; 18 CIS and proximal genes in spontaneous CzechII mammary tumors; 16 CIS and proximal genes in spontaneous Balb/cfMMTV(CZ) mammary tumors and 20 CIS and proximal genes in spontaneous Balb/cfMMTV(SP) mammary tumors (see also Tables 2 and 3). Distance numbers = base pairs.