Rectal Cancer Patient-Derived Xenografts

Patient-derived xenografts were created from biopsies from consented patients with rectal cancer prior to treatment. All animal protocols were performed in accordance with our institutional-approved protocol. Fresh tumor samples were rinsed with PBS and gentamycin (Thermo Fisher Scientific); necrotic tissue was removed, and a 2 mm³-sized tumor piece was implanted into Central Institute for Experimental Animals NOG mice (Taconic). Once tumors were of appropriate size (10 × 20 mm³), mice were sacrificed, and tumors were removed. Tumor pieces of 2 mm³ were implanted in the flank of Nude mice (Jackson Laboratories). Once tumors reached 150 mm³, mice were split into the following treatment groups: vehicle or capecitabine (100 mg/kg) and 2 Gy (Gy) radiation 5 days per week for 2 weeks. Capecitabine (LC Laboratory) was given via oral gavage. Mice were placed in a custom jig for shielding, and radiation was delivered to tumors via X-RAD 320 (Precision X-Ray, Inc) daily. Mice were weighed, and tumors were measured with calipers at least twice weekly. Tumor volumes were calculated based on caliper measurements as previously described (29 (link)). Tumors were harvested 1 week after completion of the 2-week treatment.