Cell Line Characterization and Culture Conditions

The SQ20B cell line was a gift from Dr. Anjali Gupta (The University of Iowa). The SCCVII cell line was a gift from Dr. George Weiner. The TUBO-human EGFR (TUBO-hEGFR) cell line was gifted to our lab from Dr. Yang-Xin Fu (Department of Pathology, University of Chicago, IL)^{20 (link)}, and the mEERL cell line was a gift from Dr. Paola Vermeer (Department of Surgery, University of South Dakota Sanford School of Medicine, SD)^{21 (link)}. All cell lines were authenticated by short tandem repeat profiling and used over a course of no more than 3 months after resuscitation of frozen aliquots. All cell lines were cultured in Dulbecco’s Modified Eagle’s Medium (DMEM) containing 10% fetal bovine serum (FBS) and 0.1% gentamicin, except for mEERL which was cultured in DMEM supplemented with 40.5% 1:1 DMEM/Hams F12, 10% FBS, 0.1% gentamicin, 0.005% hydrocortisone, 0.05% transferrin, 0.05% insulin, 0.0014% tri-iodo-thyronine and 0.005% EGF. Cells were cultured in a humidified incubator at 37 °C and 5% CO₂. Motolimod (VTX-2337) was purchased from AdooQ Bioscience (Irvine, CA). Cetuximab was obtained from the inpatient pharmacy at the University of Iowa Hospitals and Clinics. Human immunoglobulin G (IgG) was purchased from Sigma-Aldrich (St. Louis, MO).