American Association for Cancer Research
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Supplementary Figure 1 from Gemcitabine and CHK1 Inhibition Potentiate EGFR-Directed Radioimmunotherapy against Pancreatic Ductal Adenocarcinoma

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posted on 2023-03-31, 18:23 authored by Fares Al-Ejeh, Marina Pajic, Wei Shi, Murugan Kalimutho, Mariska Miranda, Adnan M. Nagrial, Angela Chou, Andrew V. Biankin, Sean M. Grimmond, Michael P. Brown, Kum Kum Khanna

Supplementary Figure 1: Sensitization of PANC-1 cells to gemcitabine and EGFR-directed RIT by Chk1 inhibition. (A) Adherent cultures of the PDAC PANC-1 cell line were treated in the absence or presence of escalating doses of gemcitabine, in the absence of presence of Chk1i alone (PF-477736, 180 nM) or the combinations. Chk1i was added either 16 hours after gemcitabine or concurrently. Cells were collected 24-96 hours after treatment for standard cell cycle analysis by DNA content using FACS. (B) PANC-1 cells were treated with escalating concentrations of 177Lu-anti-EGFR mAb (RIT) to achieve the specified radiation doses (0-4 Gy) over 72 hours of incubation. RIT was performed alone or in combination with Chk1i (180 nM) and then clonogenic survival was determined by standard assays. Chk1i alone at 180 nM did not have any effect on clonogenic survival (data not shown). (C) PANC-1 cells were left untreated (vehicle control, data not shown) or incubated with anti-EGFR mAb (unlabeled, control which was not different from the vehicle control), 177Lu-DOTA, 177Lu-labelled mAb with irrelevant specificity (Sal5, raised against Salmonella antigen) or 177Lu-anti-EGFR mAb (2 Gy over 72 hours). Cells were washed 3 hours after incubation to remove unbound material and left untreated or treated with Chk1i alone (180 nM), gemcitabine alone (40 ng/mL) or the combination (Chk1i+gemcitabine) before standard clonogenic survival assays.



Purpose: To develop effective combination therapy against pancreatic ductal adenocarcinoma (PDAC) with a combination of chemotherapy, CHK1 inhibition, and EGFR-targeted radioimmunotherapy.Experimental Design: Maximum tolerated doses were determined for the combination of gemcitabine, the CHK1 inhibitor PF-477736, and Lutetium-177 (177Lu)–labeled anti-EGFR antibody. This triple combination therapy was investigated using PDAC models from well-established cell lines, recently established patient-derived cell lines, and fresh patient-derived xenografts. Tumors were investigated for the accumulation of 177Lu-anti-EGFR antibody, survival of tumor-initiating cells, induction of DNA damage, cell death, and tumor tissue degeneration.Results: The combination of gemcitabine and CHK1 inhibitor PF-477736 with 177Lu-anti-EGFR antibody was tolerated in mice. This triplet was effective in established tumors and prevented the recurrence of PDAC in four cell line–derived and one patient-derived xenograft model. This exquisite response was associated with the loss of tumor-initiating cells as measured by flow cytometric analysis and secondary implantation of tumors from treated mice into treatment-naïve mice. Extensive DNA damage, apoptosis, and tumor degeneration were detected in the patient-derived xenograft. Mechanistically, we observed CDC25A stabilization as a result of CHK1 inhibition with consequent inhibition of gemcitabine-induced S-phase arrest as well as a decrease in canonical (ERK1/2 phosphorylation) and noncanonical EGFR signaling (RAD51 degradation) as a result of EGFR inhibition.Conclusions: Our study developed an effective combination therapy against PDAC that has potential in the treatment of PDAC. Clin Cancer Res; 20(12); 3187–97. ©2014 AACR.