Table 2.
Tumor-initiating capacity of sorted pancreatic cancer cells*
| No. of cells injected | Tumor incidence† |
|||
| Unsorted cells | ALDH+ cells | CD44+CD24+ cells | ALDH+CD44+CD24+ cells | |
| 10 000 | 3/17 | ND | ND | ND |
| 1250–5000 | 0/14 | 6/14 | 4/8 | 8/15 |
| 250–1000 | 0/12 | 2/6 | 2/6 | 6/14 |
| 50–200 | ND | 2/10 | 2/10 | 5/14 |
| Total | 3/43 | 10/30 | 8/24 | 19/43 |
| OR (95% CI) | 1.00 (referent) | 6.64 (1.76 to 24.97) | 6.64 (1.67 to 26.35) | 10.38 (3.02 to 35.63) |
| P‡ | .005 | .007 | <.001 | |
Unsorted and sorted human pancreatic cancer cells derived from low-passage xenografts (n = 6) were subcutaneously injected into nonobese diabetic/severe combined immunodeficient mice (one to two injections per mouse). Each xenograft was treated as an independent experiment (or group). For each xenograft, 10–14 mice were used. This table shows the data for all of the xenografts combined. The mice were monitored daily for 20 weeks for tumor formation (arbitrarily scored as a tumor >1 cm in the greatest dimension), at which time they were killed. CI = confidence interval; ND = not done; OR = odds ratio.
Tumor incidence = the number of tumors formed/the total number of injections.
Two-sided χ2 test from a generalized estimation equation approach to modeling tumor formation that accounts for the correlation between injections per mouse.