Date of Award

2014

Degree Name

Biomedical Sciences

College

Joan C. Edwards School of Medicine

Type of Degree

Ph.D.

Document Type

Dissertation

First Advisor

Pier Paolo Claudio

Second Advisor

Richard Egleton

Third Advisor

W. Elaine Hardman

Fourth Advisor

Jagan Valluri

Fifth Advisor

Hongwei Yu

Abstract

Isothiocyanates (ITCs) are natural phytochemicals produced by cruciferous vegetables. Recent evidence supports that, in addition to cancer prevention, ITCs can use various mechanisms to target malignant cells. Current therapies for cancer often provoke detrimental side effects, however clinical evidence supports that ITCs have little to no side effects in patients. Consequently, ITCs may be a promising treatment option for cancer patients, especially patients suffering from head and neck squamous cell carcinoma (HNSCC).

Despite recent improvements in cancer treatment, overall survival of advanced HNSCC has not improved in the past three decades. Metastasis and chemoresistance represent two detrimental events that greatly hinder the outcome for those suffering with HNSCC. Thus, new therapeutic options to enhance survival of patients with advanced HNSCC are needed. Several types of ITCs can be used to target HNSCC, however our studies indicated that benzyl isothiocyanate (BITC) elicits the strongest anti-tumor response when targeting chemoresistant and metastatic HNSCC cell lines.

In our in vitro studies, we evaluated the use of BITC as a treatment for HNSCC. Our study had three objectives; the first being to investigate if this compound can prevent HNSCC cell migration and invasion, the second was to study if BITC could enhance the effects of chemotherapy, and the third was to identify a mechanism through which BITC was eliciting its anti-tumor response.

Our in vitro data suggests that treatment with BITC significantly reduced the viability of multiple HNSCC cell lines tested (HN12, HN8, and HN30), but not a normal keratinocyte cell line (HAK). BITC treatments also decreased the migration and invasion of the HN12 cell line, in a dose dependent manner, at concentrations that did not affect cell viability. Additionally, when compared to either BITC or cisplatin treatment alone, the reduction in HNSCC cell viability was greater if a pretreatment of BITC was followed by a treatment of cisplatin.

Furthermore, the expression of the epithelial-mesenchymal transition (EMT) marker, vimentin, was significantly reduced after a BITC treatment in the HN12 cell line. We also observed that BITC treatments significantly increased the amount of reactive oxygen species (ROS) in HNSCC cells. Blocking BITC induced ROS with co-administration of catalase or N- acetyl-L-cysteine (NAC) significantly inhibited BITC’s ability to prevent cellular migration. Co-administration of NAC with BITC prior to cisplatin treatment reduced cytotoxicity as compared to BITC pre-treatment followed by cisplatin. Therefore, indicating that co-administration of anti-oxidants with BITC could alter the clinical efficacy BITC.

Taken together these data suggest that BITC has the capacity to inhibit processes involved in HNSCC cell migration and invasion, as well as add to the effectiveness of chemotherapy, and both of these events are regulated by BITC induced ROS.

Subject(s)

Cancer - Prevention - Research.

Cancer - Nutritional aspects - Research.

Vegetables in human nutrition.