Radioimmunotherapy with an antibody to the HPV16 E6 oncoprotein is effective in an experimental cervical tumor expressing low levels of E6

Figures & data

Figure 1 Diagram illustrating the mechanism of cervical cancer RIT with radiolabeled E6 or E7-binding mAbs. E6 and E7 proteins become accessible to mAbs in the non-viable cells and in the interstitial space as a consequence of cellular turnover in a fast-growing tumor. The mAbs bind to accessible E6 and E7 and deliver cytotoxic radiation to the tumor. Viable cancer cells are killed by radiation penetrating several cells diameters (so called “cross-fire” effect). CC, cervical cancer.

Figure 2 Western blot of cervical tumor cell lysates showing E6 and E7 expression: (A) E6 and E7 in tumor tissues from 4 patients with metastatic cervical cancer. P1–P4, Patients 1–4; (B) E6 in CasKi tumor (line 1) and in patient tumor (line 2); (C) E6 in patient tumor (line 1) and in SiHa tumor (line 2).

Figure 3 Influence of proteasome inhibitor MG132 on the levels of E6 in SiHa cells in vitro and in vivo: (A) SiHa cells in vitro treated with 0, 5, 10 and 25 µg/ml MG132 (lines 1–4, respectively) for 3 hrs; (B) SiHa tumors from nude mice. Tumor in line 1 is from a mouse treated with 20 µg MG132 with tumor being removed 3 hrs after is from the control mouse treatment; tumor in line 2 is from the control untreated mouse.

Figure 4 Tumor size in SiHa tumor-bearing mice treated with: 200 µCi ¹⁸⁸Re-C1P5 mAb; matching amount (6 µg) of “cold” C1P5 mAb; 20 µg MG-132 followed by 200 µCi ¹⁸⁸Re-C1P5 mAb 3 hr later; 20 µg MG-132; 200 µCi ¹⁸⁸Re-18B7 control mAb; or left untreated. On day 12 one mouse in control group was sacrificed because tumor diameter exceeded 1 cm. T_o, tumor diameter on the day of treatment; T_n, tumor diameter on the day of measurement.

Figure 5 H&E histology of SiHa tumors from the following treatment groups in the RIT experiment: (A) 200 µCi ¹⁸⁸Re-C1P5 mAb; (B) 20 µg MG-132 followed by 200 µCi ¹⁸⁸Re-C1P5 mAb 3 hr later; (C) untreated; (D) “cold” C1P5 mAb; (E) 20 µg MG-132; (F) 200 µCi ¹⁸⁸Re-18B7 control mAb. Original magnification ×100.

Table 1 p values for comparison of tumor sizes in E6-specific treatment groups ¹⁸⁸Re-C1P5 mAb alone and in MG132 plus ¹⁸⁸Re-C1P5 mAb to control groups in RIT experiment

Control group	Days post-treatment
	E6-specific treatment groups	3	6	9	12	15	18	21	24	27	30
Untreated	^188Re-C1P5	0.04	0.04	0.02	0.02	0.01	0.003	0.01	-	-	-
	MG132 plus ^188Re-C1P5	0.02	0.03	0.02	0.04	0.04	0.002	0.002	-	-	-
MG132 alone	^188Re-C1P5	0.04	0.03	0.02	0.02	0.02	0.01	0.01	0.01	0.04	0.04
	MG132 plus ^188Re-C1P5	0.04	0.05	0.04	0.04	0.03	0.03	0.002	0.003	0.04	0.05
Cold C1P5	^188Re-C1P5	0.05	0.02	0.02	0.01	0.005	0.008	0.01	0.02	0.04	0.04
	MG132 plus ^188Re-C1P5	0.06	0.06	0.04	0.05	0.04	0.05	0.06	0.06	0.1	0.1
^188Re-18B7	^188Re-C1P5	0.04	0.02	0.03	0.02	0.01	0.02	0.04	0.04	0.04	0.05
	MG132 plus ^188Re-C1P5	0.1	0.1	0.06	0.07	0.04	0.04	0.04	0.06	0.1	0.2

The differences between the tumor sizes for differently treated groups were analyzed by non-parametric Mann-Whitney test. Statistically significant p values are in bold. “-” indicates the absence of the surviving mice in a particular group.