Abstract 5040: Overcoming chemotherapy resistance via KISS1-mediated Cisplatin sensitization in HNSCC
Authors: Jiffar Tilahun , Yilmaz Turker , Kupferman Michael 
Published: February 2011

Abstract
Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide. While surgery and radiotherapy have traditionally been the modalities of choice for most disease sites in the head and neck, the integration of cisplatin (CDDP)-based systemic therapy has led to improvements in local and regional control of disease for patients with HNSCC. To elucidate the biological mechanisms underpinning cisplatin resistance in HNSCC, we developed a cell-based model of drug resistance by long-term exposure of tumor cell lines to escalating doses of CDDP over a 6-month period. We next tested the isogenic lineage of the OSC19CR (Cisplatin Resistant) cells by short tandem repeat genotyping (STR) and confirmed that by DNA genetic fingerprinting, the OSC19CR cells were identical to the parental OSC19 cell lines. We then utilized a flank model in mice to assess the in vivo biological behavior of the CDDP-resistant cells, and observed a signficant enhancement of both local tumor growth and distant metastasis in the OSC19CR cells, compared to the parental cells. Utilizing micro-CT imaging, we identified radiographically-visible pulmonary metastasis in the mice harboring the CDDP-resistant tumors, but not in the parental OSC19 mice. Further, in an orthotopic model of HNSCC, OSC19CR tumors were associated with adverse survival, compared to the parental OSC19 tumors. These findings suggested that CDDP resistance is associated with a biologically aggressive behavior, similar to that observed in human cancers. We next undertook a systems biology-based approach to elucidate the molecular mechanisms associated with the observed biological phenotype. Utilizing a high-throughput genomics-based approach, we identified a signficant decrease in KiSS1 expression in the OSC19CR cell line, compared to the parental cells. We further confirmed these observations utilizing end-point PCR, and also observed complete loss of KiSS1 at the protein level. Array CGH analysis identified no significant regions of genomic loss suggesting that transcriptional suppression may explain KiSS1 loss in CDDP resistant cell. To directly assess the role of KiSS1, the OSC19CR cells were stably transfected with a plasmid harboring the KiSS1 gene, which resulted in restoration of KiSS1 expression in the OSC19CR cells (OSC19CR-KiSS1). Wound scratch assays revealed that cellular migration was downregulated, but not completely abrogated, which suggested that the aggressive in vivo behavior may be due in part to the loss of KiSS1 in the OSC19CR cells. To confirm these findings either OSC19CR or OSC19CR-KiSS1 cells were inoculated into the tongues of nude mice. Survival studies revealed significant improvement in mouse viability in the OSC19CR-KiSS1 mice, with a rate that approximated the survivorship in the parental OSC19 cells. These studies provided further direct evidence for the role of KiSS1 in biologically aggressive HNSCC
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5040.