Defense Date


Document Type


Degree Name

Doctor of Philosophy



First Advisor

Paul Dent

Second Advisor

Sarah Spiegel

Third Advisor

Charles Clevenger

Fourth Advisor

Frank Fang

Fifth Advisor

Devanand Sarkar


The cancers of liver, colon and breast are amongst the top five most prevalent and most fatal worldwide. As the Raf/MEK/ERK pathway is frequently deregulated in hepatocellular carcinoma (HCC), sorafenib, a Raf kinase inhibitor, became the first systemic therapy approved for the treatment of patients with HCC. However, sorafenib only produced modest effects with low response rates in the clinic. Similarly, regorafenib, which was approved for the treatment of metastatic colorectal cancer (CRC), has had a poor response rate in the clinic. Since phosphodiesterase type 5 has been reported to be overexpressed in HCC and CRC, we hypothesized that sildenafil, a phosphodiesterase type 5 inhibitor, could enhance the toxicities of sorafenib and regorafenib in HCC and CRC cells, respectively. Our in vitro data indicated that the drugs interacted strongly to kill cancer cells via induction of ER stress, autophagy and apoptosis. In accordance with these findings, our in vivo data demonstrated a significant reduction in tumor growth.

The second study in this manuscript was conducted based on the growing body of evidence about the significant contribution of EGFR and JAK/STAT signaling to the breast tumorigenesis. Our preliminary in vitro data demonstrated that the concurrent inhibition of these two pathways by lapatinib, a dual ERBB1/2 inhibitor, and ruxolitinib, a JAK1/2 inhibitor, synergistically killed breast cancer cells of all types, including the resistant triple negative subtype. Our mechanistic studies showed that the combination of ruxolitinib and lapatinib triggered cytotoxic mitophagy, and autophagy-dependent activation of BAX and BAK leading to the mitochondrial dysfunction.


© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission