Proof of Concept Study for Increasing Tenascin-C-Targeted Drug Delivery to Tumors Previously Subjected to Therapy: X-Irradiation Increases Tumor Uptake

SIMPLE SUMMARY: We hypothesized that an agent recognizing a specific factor, which is involved in tissue injury repair, could achieve the goal of delivering an additional antitumor agent to tumors during tissue repair after initial anticancer therapy. To demonstrate our concept, the present study employed tenascin-C (TNC) as a target molecule and radiation as initial therapy. Increased TNC expression was observed in tumors after radiation exposure in a pancreatic cancer mouse model. Of our three anti-TNC antibodies, the antibody 3–6 showed statistically significant higher tumor uptake compared with non-irradiated tumors in the by biodistribution and single-photon emission computed tomography with computed tomography studies. This finding strongly supports our concept. Our proposed therapeutic strategy could result in better outcomes for patients with treatment-refractory cancer. ABSTRACT: In treatment-refractory cancers, tumor tissues damaged by therapy initiate the repair response; therefore, tumor tissues must be exposed to an additional burden before successful repair. We hypothesized that an agent recognizing a molecule that responds to anticancer treatment-induced tissue injury could deliver an additional antitumor agent including a radionuclide to damaged cancer tissues during repair. We selected the extracellular matrix glycoprotein tenascin-C (TNC) as such a molecule, and three antibodies recognizing human and murine TNC were employed to evaluate X-irradiation-induced changes in TNC uptake by subcutaneous tumors. TNC expression was assessed by immunohistochemical staining of BxPC-3 tumors treated with or without X-irradiation (30 Gy) for 7 days. Antibodies against TNC (3–6, 12–2–7, TDEAR) and a control antibody were radiolabeled with (111)In and injected into nude mice having BxPC-3 tumors 7 days after X-irradiation, and temporal uptake was monitored for an additional 4 days by biodistribution and single-photon emission computed tomography with computed tomography (SPECT/CT) studies. Intratumoral distribution was analyzed by autoradiography. The immunohistochemical signal for TNC expression was faint in nontreated tumors but increased and expanded with time until day 7 after X-irradiation. Biodistribution studies revealed increased tumor uptake of all three (111)In-labeled antibodies and the control antibody. However, a statistically significant increase in uptake was evident only for (111)In-labeled 3–6 (35% injected dose (ID)/g for 30 Gy vs. 15% ID/g for 0 Gy at day 1, p < 0.01), whereas limited changes in (111)In-labeled TDEAR2, 12–2–27, and control antibody were observed (several % ID/g for 0 and 30 Gy). Serial SPECT/CT imaging with (111)In-labeled 3–6 or control antibody provided consistent results. Autoradiography revealed noticeably stronger signals in irradiated tumors injected with (111)In-labeled 3–6 compared with each of the nonirradiated tumors and the control antibody. The signals were observed in TNC-expressing stroma. Markedly increased uptake of (111)In-labeled 3–6 in irradiated tumors supports our concept that an agent, such as an antibody, that recognizes a molecule involved in tissue injury repair, such as TNC, could enhance drug delivery to tumor tissues that have undergone therapy. The combination of antibody 3–6 coupled to a tumoricidal drug and conventional therapy has the potential to achieve better outcomes for patients with refractory cancer.