Combined Local Immunostimulatory Radioisotope Therapy and Systemic Immune Checkpoint Blockade Imparts Potent Antitumour Responses
Yu Chao1, Ligeng Xu1, Chao Liang1, Liangzhu Feng1, Jun Xu1, Ziliang Dong1, Longlong Tian1, Xuan Yi2, Kai Yang2* and Zhuang Liu1*
1Institute of Functional Nano & Soft Materials (FUNSOM), Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu, China.
2State Key Laboratory of Radiation Medicine and Protection, School of Radiation Medicine and Protection & School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou, Jiangsu, China.
Radiation therapy for cancer can lead to off-target toxicity and can be ineffective against hypoxic solid tumours and distant metastases. Here, we show that intratumoral injection, in mouse and rabbit xenografts and in patient-derived mouse xenografts, of a sodium alginate formulation containing catalase (Cat) labelled with the therapeutic 131I radioisotope enables long-term relief of tumour hypoxia and complete tumour elimination at low radioactivity doses. On injection, the soluble polysaccharide rapidly transforms into a hydrogel in the presence of endogenous Ca2+, fixing 131I-Cat within the tumours. We also show that local radiotherapy with a formulation that includes the immunostimulatory CpG oligonucleotide combined with systemic checkpoint blockade therapy using an anti-CTLA-4 antibody leads to metastasis inhibition and protection against tumour rechallenge. The local therapy, which uses only biocompatible components, might enable new strategies for local tumour treatments that can be combined with systemic therapeutic responses, for the inhibition of tumour metastasis and the prevention of tumour recurrence in patients with advanced-stage cancer.