Table 2

Paclitaxel efflux from histocultures of FaDu xenograft and patient tumors

Tumor Type	Initial C_medium	At 24 h Post-Treatment		At 72 h Post-Treatment		T_1/2,efflux
Tumor Type	Initial C_medium	C_medium	C_tumor	C_tumor-to-C_mediumRatio	Remaining in Tumor	T_1/2,efflux	C_medium	C_tumor	C_tumor-to-C_mediumRatio	Remaining in Tumor
	nM	nM	μM		%	nM	μM		%	h
Head and neck patient	120	1.13 ± 0.17	1.70 ± 0.44	1560 ± 514	54.8 ± 3.1	1.32 ± 0.14	1.19 ± 0.50	880 ± 300	43.3 ± 16.3	7.45 ± 3.02
Head and neck patient	1,200	7.69 ± 2.55	4.38 ± 1.99	550 ± 88	18.7 ± 6.2	10.9 ± 1.1	4.17 ± 2.77	376 ± 250	16.0 ± 5.3	3.33 ± 2.62
Ovarian patient	120	1.19 ± 0.24	0.615 ± 0.149	518 ± 60	39.8 ± 14.2	1.60 ± 0.26	0.520 ± 0.196	318 ± 97	35.7 ± 18.5	4.30 ± 0.54
Ovarian patient	1,200	12.8 ± 3.41	5.13 ± 1.32	398 ± 21	25.9 ± 8.3	16.7 ± 2.9	4.20 ± 1.79	245 ± 99	19.8 ± 6.6	5.00 ± 2.93
FaDu xenograft	120	0.989 ± 0.228	3.88 ± 1.27	4359 ± 1230^2-a	71.0 ± 6.8^2-a	1.42 ± 0.18	3.84 ± 1.04	2660 ± 473^2-a	71.8 ± 1.7^2-a	6.42 ± 3.51
FaDu xenograft	1,200	12.2 ± 1.3	23.2 ± 5.4	1800 ± 300^2-a	58.6 ± 5.4^2-a	18.9 ± 5.5	17.7 ± 3.7	1010 ± 339^2-a	45.0 ± 5.8^2-a	4.05 ± 1.21

Tumors were incubated with paclitaxel for 24 h. After replacing the drug-containing medium with drug-free medium, the drug concentration remaining in histocultures at 24 and 72 h post-treatment were analyzed to determine the time to reach 50% of the pseudo-steady-state level (T_1/2,efflux). The statistical significance of the differences among patient (head and neck and ovarian, n = 6) and FaDu (n = 3) tumors, at equal initial medium concentrations, were analyzed by unpaired t test. Note the different units used for the medium and tumor concentrations. Mean ± S.D. (n = 3). Note that some of the efflux experiments needed different tumors as in the uptake experiments reported in Table 1.

↵2-a P < .05.