Heat Shock Protein 27 as a New Therapeutic Target for Radiation Sensitization of Head and Neck Squamous Cell Carcinoma

Abstract

In a wide range of human cancers, increased levels of heat shock protein 27 (Hsp27) are closely associated with tumorigenesis, metastasis, resistance to anticancer therapeutics, and thus poor prognosis. In this study, we evaluate the radiosensitizing effects of Hsp27 gene silencing using OGX-427, a second-generation antisense oligonucleotide (ASO), on the radioresistant head and neck squamous cell carcinoma (HNSCC) SQ20B cells. In vitro, the downregulation of Hsp27 significantly enhanced radiation-induced apoptotic and clonogenic death, and promoted Akt inactivation. In vivo, combining OGX-427 with local tumor irradiation (5 x 2 Gy) led to a significant regression of SQ20B tumors related to a high rate of apoptosis and decreased levels of glutathione antioxidant defenses. Increasing the total radiation dose (15 x 2 Gy) significantly amplified the radiosensitizing effect of OGX-427. Treatment of tumors with OGX-427 plus radiation resulted in a decrease in angiogenesis associated with a reduced activation of the Akt pathway. Furthermore, the combined treatment enhanced the survival of SQ20B-bearing mice and showed no signs of acute and delayed toxicity. Our findings demonstrate for the first time that Hsp27 knockdown enhances the cytotoxic effects of radiotherapy in vivo and provide preclinical proof of principle for clinical trials using Hsp27 antisense technology in the treatment of patients with HNSCC radioresistant cancers.

Inhibition of heat shock protein 27 (HspB1) tumorigenic functions by peptide aptamers

“…Photomicrographs of tumor sections and quantification of Ki67 marker revealed that the lack of tumor development with PA11 and 50 was due to an alteration of proliferation process (Figures 6a and b). We have previously reported that a Hsp27 RNAi induces a small delay in tumor progression, without modulation of the Ki67 marker (Hadchity et al, 2009). Moreover, TUNEL assay on tumor section showed that PA11 and PA50 did not increase apoptosis, probably as a result of a lack of pro-apoptotic stimulation (Figure 6a).…”

“…]) (Equation (1)), where SF is survival fraction and D represents radiation doses (Hadchity et al, 2009). The SF at 2 Gy (SF2) was determined as an index of radiosensitivity.…”

“…The morphology of tumors was assessed on formalin-fixed, paraffin-embedded tissue sections, after Giemsa staining (Hadchity et al, 2009). …”

“…Cell survival curves following irradiation were generated by means of a standard colony-formation assay (Hadchity et al, 2009). The survival a and b variables were fitted according to the linear quadratic equation…”

Impact of hyperthermic intraperitoneal chemotherapy on Hsp27 protein expression in serum of patients with peritoneal carcinomatosis

“…Antisense oligonucleotides (ASOs) are powerful tools to inhibit target gene expression in a sequence-specific manner. Thus, OGX-427 (Oncogenex), a second-generation ASO drug that in preclinical experiments significantly decreased the levels of Hsp27 and induced apoptosis, acted as a chemosensitizer in combination with gemcitabine (Baylot et al 2011) and as a radiation sensitizer in patients with radioresistant head and neck squamous cell carcinomas (Hadchity et al 2009). Phase I and II clinical trials on patients with bladder and prostate cancers that Fig.…”