Purpose: Poorly differentiated thyroid cancer and anaplastic thyroid cancer (ATC) are rare yet lethal malignancies with limited treatment options. Many malignant tumors, including papillary thyroid cancer (PTC) and ATC, are associated with increased expression of ICAM-1, providing a rationale for utilizing ICAM-1–targeting agents for the treatment of aggressive cancer. We developed a third-generation chimeric antigen receptor (CAR) targeting ICAM-1 to leverage adoptive T-cell therapy as a new treatment modality. Experimental Design: ICAM-1 CAR T cells were applied to multiple malignant and nonmalignant target cells to investigate specific target cell death and “off-tumor” toxicity in vitro. In vivo therapeutic efficacy of ICAM-1 CAR T cells was examined in ATC mouse models established from a cell line and patient-derived tumors that rapidly develop systemic metastases. Results: ICAM-1 CAR T cells demonstrated robust and specific killing of PTC and ATC cell lines in vitro. Interestingly, although certain ATC cell lines showed heterogeneous levels of ICAM-1 expression, addition of cytotoxic CAR T cells induced increased ICAM-1 expression such that all cell lines became targetable. In mice with systemic ATC, a single administration of ICAM-1 CAR T cells mediated profound tumor killing that resulted in long-term remission and significantly improved survival. Patient-derived ATC cells overexpressed ICAM-1 and were largely eliminated by autologous ICAM-1 CAR T cells in vitro and in animal models. Conclusions: Our findings are the first demonstration of CAR T therapy against both a metastatic, thyroid cancer cell line and advanced ATC patient-derived tumors that exhibit dramatic therapeutic efficacy and survival benefit in animal studies. Clin Cancer Res; 23(24); 7569–83. ©2017 AACR.

While the majority of thyroid cancer patients are easily treatable, those with anaplastic or poorly differentiated recurrent thyroid carcinomas have a very poor prognosis with a median survival of less than a year. Previously, we have shown a significant correlation between ICAM-1 overexpression and malignancy in thyroid cancer, and have pioneered the use of ICAM-1 targeted CAR T cells as a novel treatment modality. For clinical translation of this novel modality, we designed CAR T cells possessing micromolar rather than nanomolar affinity to ICAM-1 to avoid cytotoxicity in normal cells with basal levels of ICAM-1 expression. Herein, we report the automated process of CAR T cell manufacturing with CliniMACS Prodigy (Miltenyi Biotec) using cryopreserved peripheral blood leukocytes from apheresis collections. Using Prodigy, thawed leukopak cells were enriched for CD4⁺and CD8⁺T cells, subjected to double transduction using lentiviral vector, and expanded in culture for a total of 10 days with a final yield of 2–4 × 10⁹cells. The resulting CAR T cells were formulated for cryopreservation to be used directly for infusion into patients after thawing with no further processing. We examined cross-reactivity of CAR T cells toward both human and murine ICAM-1 and ICAM-1 expression in human and mouse tissues to demonstrate that both efficacy and on-target, off-tumor toxicity can be studied in our preclinical model. Selective anti-tumor activity in the absence of toxicity provides proof-of-concept that micromolar affinity tuned CAR T cells can be used to target tumors expressing high levels of antigen while avoiding normal tissues expressing basal levels of the same antigen. These studies support the initiation of a phase I study to evaluate the safety and potential efficacy of micromolar affinity tuned CAR T cells against newly diagnosed anaplastic and refractory or recurrent thyroid cancers.

Context: The RAF inhibitor vemurafenib has provided a major advance for the treatment of patients with BRAF-mutant metastatic melanoma. However, BRAF-mutant thyroid cancer is relatively resistant to vemurafenib, and the reason for this disparity remains unclear. Anticancer therapy–induced autophagy can trigger adaptive drug resistance in a variety of cancer types and treatments. To date, role of autophagy during BRAF inhibition in thyroid cancer remains unknown. Objective: In this study, we investigate if autophagy is activated in vemurafenib-treated BRAF-mutant thyroid cancer cells, and whether autophagy inhibition improves or impairs the treatment efficacy of vemurafenib. Design: Autophagy level was determined by western blot assay and transmission electron microscopy. The combined effects of autophagy inhibitor and vemurafenib were assessed in terms of cell viability in vitro and tumor growth rate in vivo. Whether the endoplasmic reticulum (ER) stress was in response to vemurafenib-induced autophagy was also analyzed. Results: Vemurafenib induced a high level of autophagy in BRAF-mutant thyroid cancer cells. Inhibition of autophagy by either a pharmacological inhibitor or interfering RNA knockdown of essential autophagy genes augmented vemurafenib-induced cell death. Vemurafenib-induced autophagy was independent of MAPK signaling pathway and was mediated through the ER stress response. Finally, administration of vemurafenib with the autophagy inhibitor hydroxychloroquine promoted more pronounced tumor suppression in vivo. Conclusions: Our data demonstrate that vemurafenib induces ER stress response–mediated autophagy in thyroid cancer and autophagy inhibition may be a beneficial strategy to sensitize BRAF-mutant thyroid cancer to vemurafenib.

BACKGROUND: Preoperative B‐type Raf kinase Val600Glu mutation, or BRAF(V600E), analysis has been proposed as a tool to guide initial surgery for indeterminate thyroid nodules. This study sought to determine if cytologic markers of malignancy are associated with the BRAF(V600E) mutation and if preoperative BRAF(V600E) testing would alter the initial management of patients with indeterminate nodules.METHODS: Patients who underwent surgery for a thyroid nodule between 2003 and 2012 at a tertiary care center were prospectively enrolled. Stored nodule samples were retrospectively genotyped for the BRAF(V600E) mutation. BRAF(V600E) status, demographics, cytologic and histopathologic findings, and choice of initial surgery were examined.RESULTS: A total of 960 patients were enrolled, of which 310 (32%) had an indeterminate nodule. The BRAF(V600E) mutation was identified in 13 patients (4%), 12 of whom had either cytologic atypia or were Bethesda category V. Three percent of Bethesda category III or IV nodules that were malignant harbored the mutation compared with 42% of Bethesda category V malignancies. Nuclear grooves (P = .030), pseudoinclusions (P < .001), and oval nuclei (P = .022) were all more common among BRAF(V600E) mutants. The sensitivities of using BRAF testing alone, cytologic atypia/Bethesda category V classification, or both, were 15%, 73%, and 76%, respectively. Twelve of the 13 BRAF(V600E) mutants had total thyroidectomies initially due to worrisome cytologic features, and therefore the initial management of only one patient would have been altered if BRAF(V600E) testing had been performed preoperatively.CONCLUSIONS: Preoperative mutation screening for BRAF(V600E) does not meaningfully improve risk stratification and is unlikely to alter the initial management of patients with indeterminate nodules. Cancer 2013. © 2012 American Cancer Society.