Abstract

Introduction: Oral squamous cell carcinoma (OSCC) ranks as one of the common cancers in the world1. OSCC develops from the epithelium of the oral cavity, including the tongue, lips, and floor of the mouth, cheeks, hard palate, or other unspecified parts of the mouth. The surgical resection of the primary tumor is a standard approach to the treatment of oral cancers, which is most commonly followed by adjuvant chemotherapy and/or radiotherapy depending on the risk features or for locally advanced disease. Adjuvant chemo and/or radiotherapy provide a significant survival advantage in the presence of positive margins and/or lymph node spread2. However, appropriate target selection is still a concern in the adjuvant management of oral cavity carcinoma. There is a need to decide a target and the dose which can minimize the risk of marginal recurrences and at the same time do not cause toxic effects to sensitive healthy tissues which affects the quality of life of patients. Nanotechnology offers to enhance the dose of radiation at the tumor region by using radiosensitizing nanoparticles. These radiation enhancing agents increase the effect of radiation in the tumor region while maintaining clinical constrains on the healthy tissue. Here, we report the use of 100nm theranostic nanoparticles (TNPs) with combined MR contrast that can enable pre-procedure radiotherapy planning, as well as enhance radiation treatment efficacy.
Methods: TNPs were synthesized by the method as previously published by us3. TNPs composed of NIR plasmon-resonant core (GNRs) and a Gd (III) inorganic layer as the shell. Au core was first synthesized using a seed-mediated growth process4 followed by sodium oleate coating at 80°C for 1 h. Uniform Gd (III) shell was achieved in the presence of hexamethylenetetramine at 120 °C for 3 h. These TNPs were surface functionalized with –NH2 and then conjugated with mPEG5k-COOH to obtain a neutral surface charge. These TNPs have both X-ray and MR contrast. TNS were calibrated for X-ray contrast at 60 kV on a Pxinc’s X-RAD SmART scanner using a cone beam CT. MR contrast was determined on a Brukur 9.4T small animal and GE 7T human scanners. Human oral squamous cancer cell (OSC-19-GFP-luc) were orthotopically implanted in the tongue of immune compromised rats. The efficacy of TNPs in enhancing radiation therapy response was tested via systemic (tail vein) delivery (1μL/g of 1*1013 TNPs). Rats bearing tumors were randomized to saline+radiation (n=4) or TNPs+radiation (n=5) groups. 8-Gy single dose radiation under MRI guidance was provided 4h post tail vein injection. Rats were followed via bioluminescence imaging for 4 weeks.
Results: PEGylated TNPs demonstrated both X-ray and MR contrast in a dose linearly dependent manner. The T1 relaxivity at 9.4T was found to be ~1.1x108 mM–1S–1 in terms of TNPs concentration. The average TNP size was 75 nm and zeta potential ~4.8 mV indicating long circulation potential. Tumors were clearly delineated in MRI images after i.v. injection of TNPs (Fig. 1A). MRI images showed optimal tumor-to-background ratio at 4h post injection (Fig. 1B). Following image guided radiation therapy (IGRT) treatment, tumors in TNPs treated rats' experienced reduced tumor growth (Fig. 1C and D) while rats treated with radiation alone increased tumor growth. After 4 weeks of follow up, lung metastasis was observed in rats treated with radiation alone while lungs were clear in TNPs treated rats’. These results indicate the therapeutic efficacy of TNPs in combination with IGRT.
Discussion: TNPs allow an accurate demarcation of the tumor and also increase efficiency of radiation treatment.
Conclusions: TNPs with combined MR contrast can enable pre-procedure radiotherapy planning, as well as enhance radiation treatment efficacy.

Summary

We report the use of 100nm theranostic nanoparticles (TNPs) with combined MR and X-ray contrast that can enable pre-procedure radiotherapy planning, as well as enhance radiation treatment efficacy.

Acknowledgements

The authors thank the Alliance for Healthy Wisconsin and Rock River Cancer Research Foundation (RRCRF, A.J.) for support.