131I-recombinant human EGF has antitumor effects against MCF-7 human breast cancer xenografts with low levels of EGFR

Evaluation of therapeutic effectiveness of 131I-antiEGFR-BSA-PCL in a mouse model of colorectal cancer

AIM: To investigate the biological effects of internal irradiation, and the therapeutic effectiveness was assessed of ¹³¹I-labeled anti-epidermal growth factor receptor (EGFR) liposomes, derived from cetuximab, when used as a tumor-targeting carrier in a colorectal cancer mouse model.

METHODS: We described the liposomes and characterized their EGFR-targeted binding and cellular uptake in EGFR-overexpressing LS180 colorectal cancer cells. After intra-tumor injections of 74 MBq (740 MBq/mL) ¹³¹I-antiEGFR-BSA-PCL, we investigated the biological effects of internal irradiation and the therapeutic efficacy of ¹³¹I-antiEGFR-BSA-PCL on colorectal cancer in a male BALB/c mouse model. Tumor size, body weight, histopathology, and SPECT imaging were monitored for 33 d post-therapy.

RESULTS: The rapid radioiodine uptake of ¹³¹I-antiEGFR-BSA-PCL and ¹³¹I-BSA-PCL reached maximum levels at 4 h after incubation, and the ¹³¹I uptake of ¹³¹I-antiEGFR-BSA-PCL was higher than that of ¹³¹I-BSA-PCL in vitro. The ¹³¹I tissue distribution assay revealed that ¹³¹I-antiEGFR-BSA-PCL was markedly taken up by the tumor. Furthermore, a tissue distribution assay revealed that ¹³¹I-antiEGFR-BSA-PCL was markedly taken up by the tumor and reached its maximal uptake value of 21.0 ± 1.01 %ID/g (%ID/g is the percentage injected dose per gram of tissue) at 72 h following therapy; the drug concentration in the tumor was higher than that in the liver, heart, colon, or spleen. Tumor size measurements showed that tumor development was significantly inhibited by treatments with ¹³¹I-antiEGFR-BSA-PCL and ¹³¹I-BSA-PCL. The volume of tumor increased, and treatment rate with ¹³¹I-antiEGFR-BSA-PCL was 124% ± 7%, lower than that with ¹³¹I-BSA-PCL (127% ± 9%), ¹³¹I (143% ± 7%), and normal saline (146% ± 10%). The percentage losses in original body weights were 39% ± 3%, 41% ± 4%, 49% ± 5%, and 55% ± 13%, respectively. The best survival and cure rates were obtained in the group treated with ¹³¹I-antiEGFR-BSA-PCL. The animals injected with ¹³¹I-antiEGFR-BSA-PCL and ¹³¹I-BSA-PCL showed more uniform focused liposome distribution within the tumor area.

CONCLUSION: This study demonstrated the potential beneficial application of ¹³¹I-antiEGFR-BSA-PCL for treating colorectal cancer. ¹³¹I-antiEGFR-BSA-PCL suppressed the development of xenografted colorectal cancer in nude mice, thereby providing a novel candidate for receptor-mediated targeted radiotherapy.

Biodistribution and anti-tumor efficacy of intratumorally injected necrosis-avid theranostic agent radioiodinated hypericin in rodent tumor models

Hypericin has an excellent necrosis-specific targeting capacity; thus, we explored small-molecular tumor necrosis therapy (SMTNT) for inhibiting tumor growth in rodent tumor models. H22 and S180 tumor-bearing Kunming (KM) mice were intratumorally injected with (131)I-monoiodohypericin ((131)I-MIH) to investigate the biodistribution of (131)I-MIH as a function of time. Single-photon emission computed tomography (SPECT), autoradiography, fluorescence microscopy and hematoxylin and eosin (H&E) staining were performed to determine the intra-tumoral distribution of (131)I-MIH. A therapeutic evaluation study was also performed in the tumor-bearing KM mice using saline and a positive drug as controls. Gamma counting, SPECT images, autoradiography and fluorescence microscopy and H&E staining results revealed intense retention of (131)I-MIH in the necrotic tumor over 168 h and good in vivo stability of the agent. Therapy with a single dose of intra-tumoral administration of (131)I-MIH caused significant tumor growth delay. A histopathological analysis of the tumors and normal organs further validated the therapeutic efficacy and limited systemic toxicity of (131)I-MIH. The prolonged tumor retention and effective therapy indicated that (131)I-MIH may be a promising intratumorally injected SMTNT agent.

Injectable intratumoral depot of thermally responsive polypeptide-radionuclide conjugates delays tumor progression in a mouse model

This study evaluated a biodegradable drug delivery system for local cancer radiotherapy consisting of a thermally sensitive elastin-like polypeptide (ELP) conjugated to a therapeutic radionuclide. Two ELPs (49 kDa) were synthesized using genetic engineering to test the hypothesis that injectable biopolymeric depots can retain radionuclides locally and reduce the growth of tumors. A thermally sensitive polypeptide, ELP(1), was designed to spontaneously undergo a soluble-insoluble phase transition (forming viscous microparticles) between room temperature and body temperature upon intratumoral injection, while ELP(2) was designed to remain soluble upon injection and to serve as a negative control for the effect of aggregate assembly. After intratumoral administration of radionuclide conjugates of ELPs into implanted tumor xenografts in nude mice, their retention within the tumor, spatio-temporal distribution, and therapeutic effect were quantified. The residence time of the radionuclide-ELP(1) in the tumor was significantly longer than the thermally insensitive ELP(2) conjugate. In addition, the thermal transition of ELP(1) significantly protected the conjugated radionuclide from dehalogenation, whereas the conjugated radionuclide on ELP(2) was quickly eliminated from the tumor and cleaved from the biopolymer. These attributes of the thermally sensitive ELP(1) depot improved the antitumor efficacy of iodine-131 compared to the soluble ELP(2) control. This novel injectable and biodegradable depot has the potential to control advanced-stage cancers by reducing the bulk of inoperable tumors, enabling surgical removal of de-bulked tumors, and preserving healthy tissues.