Category: Assay Development and Screening
Only 5.1% of new cancer drug candidates advance through phase I clinical trials to FDA approval. Cancer drugs fail due to unacceptable toxicity, little to no efficacy, or poor bioavailability. One strategy to reduce potential drug failures and better correlate clinical efficacy to in vitro studies would be to implement models better able to recapitulate the complexities of human solid tumors. A growing body of evidence supports that 3D multicellular tumor spheroids (MCTS) are more representative of solid tumors than traditional 2D cell monolayer cultures. MCTSs provide a 3D structure and microenvironment capable of cell-cell and cell-ECM interactions more akin to cells in a solid tumor. In addition, MCTSs allow for the formation of differential gradients of nutrients, oxygen, and waste products that result in differential zones of proliferation not observed in 2D monolayer cultures. Head and neck squamous cell carcinoma (HNSCC) is the eighth leading cause of cancer worldwide, with ~550,000 new cases yearly and approximately 300,000 ending in mortality. Despite strides in surgical, radiological, and pharmacological therapies, 5-year survival rates have remained static at 40-50% for the past several decades. In addition, surgical and radiation therapies can leave patients with lasting impairments and deformities to regions of the head and neck. Currently only 7 drugs are approved for HNSCC treatment including: cisplatin, docetaxel, fluorouracil, methotrexate, bleomycin, and most recently, the targeted therapies cetuximab and nivolumab. There is a drastic unmet need for improved anticancer therapies for HNSCC. We describe here the characterization of MCTSs formed from 11 HNSCC cell lines into 5 distinct phenotypes; rapid progressive growth, slow progressive growth, dormant, slow progressive death, and rapid progressive death. These phenotypes encompass differences in spheroid morphology, proliferation, and viability over time. We used optimized MCTS and traditional 2D monolayer growth inhibition assays to directly compare the potencies of 20 anticancer drugs, including those approved for HNSCC. We selected 5 HNSCC cell lines representative of four of the five MCTS phenotypes. For 8-11 (40-55%) of the drugs, 2D HNSCC monolayers were considerably more sensitive than MCTS cultures where no apparent cytotoxicity was detectable, and 2D GI50 values were minimally > 5-fold to 260-fold lower than in MCTSs. Interestingly, 4 drugs (20%) were capable of >50% growth inhibition in both 2D monolayer and MCTS cultures across all HNSCC cell lines; cisplatin, doxorubicin, everolimus, and sunitinib. Whether the apparent differences in drug sensitivity between 2D monolayer and MCTS HNSCC cultures are due to the varied microenvironments and/or drug penetration and distribution barriers of MCTSs are under investigation. Our studies support the hypothesis that MCTSs represent more relevant in vitro culture models that have the potential to better mimic drug responses observed in solid tumors in vivo.
Stanton Kochanek– Graduate Student, University of Pittsburgh School of Pharmacy, Pittsburgh, PA
University of Pittsburgh School of Pharmacy
A graduate of John Carroll University in Cleveland, Ohio, Stanton is currently pursuing a PhD in Pharmaceutical Sciences at the University of Pittsburgh's School of Pharmacy. The focus of his research relates to cancer pharmacology, specifically, identifying synergistic drug combinations for the treatment of several different cancer types, characterizing various head and neck squamous cell carcinoma cell lines in a 3-dimensional model of cell culture called multicellular tumor spheroids, and using multicellular tumor spheroids as a model to predict drug efficacy in vivo. Stanton is also an avid Latin dancer, both teaching and performing nationally and internationally.