David T. Dicker

Abstract P6-02-01: Elucidating the change of TRAIL sensitivity in basal like TNBC cell lines by lapatinib, and further therapeutic implication

Triple negative breast cancer (TNBC) comprises 15-20% of breast cancer, and carries a poor prognosis. Recently, efforts to understand this heterogeneous group of cancers have led to recognition of different subtypes of TNBC by Dr. Pietenpol et al based on genetic and functional signature. So far, the only targeting agent for TNBC still remains as androgen receptor inhibitor for LAR group. Thus, other strategies in therapeutic development for TNBCs are necessary. TRAIL (Tumor Necrosis Factor-related apoptosis inducing ligand), a member of the TNF-alpha family of death receptor ligands, induces apoptosis by binding death receptors (DR4 and DR5), could be a good strategy in therapeutic development in TNBC. Unfortunately, majority of breast cancer cell lines are resistant to TRAIL targeted therapy especially basal like group of cells, as previously shown in the work of Lipkowitz at the NCI. Lapatinib, a well known as erbB 1 and 2 inhibitor had been found to have off target activity inducing JNK, an important activator of nuclear transcription of death receptor, and mitochondrial mediated intrinsic apoptosis pathway. Interestingly, study of combination therapy with lapatinib and TRAIL not only confirmed baseline poor sensitivity to TRAIL induced apoptosis in “basal like” HCC 1937 and MDA-MB-468 cell lines, but also revealed an unexpected difference in sensitization to TRAIL induced apoptosis by Lapatinib pre-treatment between these two cell lines. When treated with 48hrs Lapatinib high–dose treatment, HCC 1937 showed increased sensitization whereas MDA-MB-468 did not. Both HCC 1937 and MDA-MB-468 are in the same basal like 1(BL1) group by Dr. Pietenpol9s analysis, and their baseline sensitivity to TRAIL inducing apoptosis are the same. In terms of apoptosis - there are two big categories of cells. Type I cells are independent of mitochondria for the induction of Fas death receptor mediated apoptosis, where as type II cells are mitochrondria-dependent. Thus we hypothesized that this difference in lapatinib induced TRAIL sensitization between two cell lines is due to difference in one being type I vs the other being type II cell, and this type of apoptosis is not likely equal in same subgroup of TNBC. If this hypothesis is correct, targeting apoptosis pathway in TNBC should incorporate the recognition of apoptosis cell types rather than functional/genetic based subtypes. We will further elucidate our hypothesis by studying JNK, caspase 3 and 9 activity and downstream of both intrinsic, extrinsic apoptosis pathway. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-02-01.

Abstract 2943: Lapatinib restores TRAIL-mediated apoptosis in TRAIL-resistant Triple Negative Breast Cancer (TNBC) through an off-target strategy that appears to be independent of increased death receptor expression.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DCnnTriple negative breast cancer (TNBC) comprises 15-20% of breast cancer, and carries a poor prognosis. TRAIL (Tumor Necrosis Factor-related apoptosis inducing ligand), a member of the TNF-alpha family of death receptor ligands, induces apoptosis by binding death receptors (DR4 and DR5), and can be a good therapeutic target in TNBC based on the work of Lipkowitz at the NCI. Lapatinib, a dual HER2 and EGFR inhibitor has been shown to sensitize colon cancer and GBM cells to TRAIL-induced apoptosis through an off-target effect that involves JNK. In colon cancer cell lines, this sensitization was found to be due to increased DR4 and DR5 protein levels, and this was not affected by HER2 and EGFR dual specific inhibition. The majority of breast cancer cell lines including HCC 1937, a BRCA1-deficient TNBC cell line derived from a patient with BRCA1 mutation, are known to have constitutive death receptor endocytosis resulting in resistance to TRAIL. We hypothesized that treatment of TNBC cells with lapatinib may induce sensitization to TRAIL-induced apoptosis in normally TRAIL-resistant cell lines, but possibly not by increased death receptor protein expression since these cells have defective cell surface expression. MDA-MB-231 and HCC 1937 cell lines are both well-validated TNBC cell lines. MDA-MB-231 is known to be sensitive to TRAIL, whereas HCC 1937 is resistant to TRAIL. These two cell lines were pre-treated with 0-10 μM lapatinib for 48 hrs. Cells were then treated with His-tagged recombinant TRAIL (50 ng/mL) for 24 hr subsequently. Cell Titer Glo assay, and sub-G1 DNA content analysis by flow cytometry showed increments of apoptosis after lapatinib pre-treatment. This change was more prominent in HCC 1937, which is normally resistant to TRAIL-induced apoptosis. However western blotting did not show increased DR4/DR5 by pre-treatment with lapatinib in either MDA-MB-231 or HCC 1937. This result suggests that we may have identified an off-target effect of lapatinib in TNBC that appears to not involve increased death receptor expression. We are further exploring the previously described role for JNK in the off-target effect to further elucidate this TRAIL death receptor- and Her2/EGFR-independent mechanism of TRAIL sensitization by lapatinib that has implication for TNBC therapy.nnCitation Format: Bora Lim, Nathan G. Dolloff, Joshua E. Allen, David T. Dicker, Wafik S. El-Deiry. Lapatinib restores TRAIL-mediated apoptosis in TRAIL-resistant Triple Negative Breast Cancer (TNBC) through an off-target strategy that appears to be independent of increased death receptor expression. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2943. doi:10.1158/1538-7445.AM2013-2943

Abstract 3483: Modeling circulating tumor cells in the peripheral blood and CSF of breast cancer patients.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DCnnThe enumeration of circulating tumor cells (CTCs) using the CellSearch system (Veridex LLC) is a valuable prognostic clinical tool in several epithelial malignancies. Surveillance methods for metastatic disease involving the central nervous system (CNS) lack adequate sensitivity, specificity, and reproducibility in the clinic. We previously reported a method to enumerate CTCs in the cerebrospinal fluid (CSF) of breast cancer patients with metastases involving the CNS. The enumeration of CTCs in CSF by this method is highly sensitive, accurate, reproducible, and correlates with disease burden by several measures. Here, we concomitantly monitor CTCs in the peripheral blood and CSF of five patients with neoplastic meningitis receiving intrathecal (IT) chemotherapy. In each patient, CTC counts have been more sensitive than conventional cytology, and have predicted the course of symptoms and overall survival more precisely than conventional cytology. We observed a striking inverse relationship between CTC counts in the peripheral blood and CSF. This observation generated the hypothesis that CTCs migrate from the blood to the CSF and the converse as sanctuary sites during compartmentalized therapy to result in systemic disease recurrence. To test this hypothesis we created mouse models of these clinical phenomena including injection of triple-negative breast cancer into the peripheral blood or intracranially. Injection of luciferase-infected MDA-MB-231 or MDA-MB-468 human triple-negative breast cancer cells into the brain of athymic nude mice resulted in primary tumors at the site of injection. The MDA-MB-231, unlike the MDA-MB-468, generated detectable tumor cell dissemination into the CSF of inoculated mice that correlated with a significantly declined survival. CSF collected from the cisterna magna of inoculated mice corroborated these observations. Current studies are examining the impact of compartmentalized therapy on the migration of these tumor cells as well as profiling unique genetic drivers of the subset of tumors cells that disseminate into the CSF. The intercompartmental cycling of tumor cells may represent an important mechanism for disease persistence and recurrence, and suggests that concurrent systemic and CNS-directed therapy may be warranted.nnCitation Format: Joshua E. Allen, Akshal S. Patel, David T. Dicker, Jonas M. Sheehan, Michael Glantz, Wafik S. El-Deiry. Modeling circulating tumor cells in the peripheral blood and CSF of breast cancer patients. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3483. doi:10.1158/1538-7445.AM2013-3483

Abstract 608: Quinacrine and sorafenib as potential combination for anaplastic thyroid carcinoma.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DCnnAnaplastic thyroid cancer (ATC) comprises ∼2% of all thyroid cancers and its median survival rate remains poor. ATC is frequently resistant to conventional therapy and therefore it is essential to expand the number of treatment options for ATC. Proto-oncogenes RET, RAS and BRAF are some of the best targets described in thyroid cancer. Sorafenib is a small molecule multi-kinase inhibitor that inhibits RAF, MEK and ERK kinases among other targets and is therefore being evaluated in several phase II/III clinical trials in thyroid cancer. Quinacrine, a potent small molecule inhibitor of NFKB signaling, is currently being evaluated in phase II clinical trials. We have previously shown the effectiveness of quinacrine in combination with cytotoxic drugs in hepatocellular and colon carcinoma cells acts by inhibiting NFKB, Mcl-1, and angiogenesis in tumor cell lines that are deficient in p53. Here, we evaluate the efficacy of quinacrine in combination with sorafenib on a panel of human ATC cells. Quinacrine as a single agent effectively inhibits growth and promote apoptosis of ATC cells in vitro in a dose-dependent manner as assessed by CellTiter-Glo and sub-G1 analysis respectively. Combinatorial dose-response modulation of quinacrine with sorafenib suggests a synergistic drug-drug interaction with respect to growth stasis of ATC cells in vitro, as defined by Chou-Talalay. Western blot analysis suggest that the anti-apoptotic Bcl-2 family member Mcl-1, over-expressed in a number of solid tumors, is efficiently down-regulated in the ATC cell line 8505C by the combination of quinacrine and sorafenib. We also observe that the active form of transcription factor Stat3 is down-regulated by both quinacrine and sorafenib. In contrast to chloroquine that inhibits autophagy, our previous results have not shown that quinacrines anti-tumor efficacy involves alterations in autophagy. Furthermore, sorafenib and quinacrine significantly improve survival in a mouse thyroid orthotopic in vivo xenograft model of ATC. We are currently exploring the detailed molecular mechanism of the quinacrine and sorafenib drug synergy and associated anti-tumor activity in vitro and in vivo. In addition, we are exploring the possibility of performing in vivo assays of the therapy combination with clinical samples. Our findings suggest that quinacrine in combination with sorafenib may be a novel and potentially cost effective therapeutic strategy for the treatment ATC.nnCitation Format: Junaid Abdulghani, Jean-Nicolas Gallant, Tiffany Whitcomb, David Dicker, David Goldenberg, Charles D. Smith, Niklas Finnberg, Wafik S. El-Deiry. Quinacrine and sorafenib as potential combination for anaplastic thyroid carcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 608. doi:10.1158/1538-7445.AM2013-608

Abstract 3998: The IGF1 receptor/insulin receptor dual kinase inhibitor BMS-754807 targets the cancer stem cell population in addition to its synergism with Lapatinib in colorectal cancer.

Colon cancer is the second leading cause of cancer mortalities each year. Current treatment options include drugs that target the epidermal growth factor (EGF) pathway. However, the use of these drugs is limited to individuals that are wild type for KRAS. New therapies are needed for patients who develop resistance to EGF-based therapies, as well as for the 40% of patients whose tumors have mutated KRAS. Our approach has been to target pathways that regulate cancer cell metabolism. The insulin and insulin-like growth factor-1 (IGF1) pathways regulate glucose metabolism, cell growth, cell motility and anti-apoptotic pathways. In colon cancer, IGF1 and insulin enhance tumor growth, promote metastasis and increase the cancer stem cell (CSC) population. In order to target the insulin and IGF-1 pathways simultaneously, we utilized the small molecule, dual kinase inhibitor BMS-754807 which inhibits the Insulin receptor (IR) and IGF1 receptor (IGF1R) with equal potency. We previously reported that the drug effectively reduced cell viability in a panel of eight colon cancer cell lines. In combination when combined with Lapatinib, an EGFR/HER2 small molecule dual kinase inhibitor, the drug showed synergistic effects on viability in a subset of cell lines. In order to determine the mechanism of the observed synergy, we examined whether EGFR and IGF1R were interacting directly as has been observed in breast cancer. Co-immunoprecipitation experiments in colorectal cancer cells, did not demonstrate an interaction between the EGFR and IGF1R. Examination of the signaling pathways in our panel of cell lines has determined that the regulation of ERK appears to be a critical determinant in sensitivity to the combination therapy. In both of the sensitive lines, AKT was strongly activated by IGF1, while ERK was strongly activated by EGF, but less substantially by IGF1. However in the cell lines that were insensitive to the BMS-754807/Lapatinib combination, substantial activation of ERK was observed in the absence of either EGF or IGF1. Therefore constitutive ERK activation in the absence of EGF signaling may be the determinant for sensitivity to the combined therapy. Finally, we examined the efficacy of BMS-754807 in the targeting colon cancer stem cells. In our panel of eight cell lines, BMS-754807 strongly inhibited colonsphere formation from the CSC population in three cell lines, and showed moderate inhibition in four of the five remaining lines. Of interest is the fact that the cells that were most sensitive to BMS-754807 in sphere formation were the most resistant in viability assays, and did not synergize with Lapatinib. These results are encouraging as we continue to develop strategies that specifically target the cancer stem cell, and indicate that BMS-754807 has multiple potential mechanisms of action in colon cancer. Citation Format: Kristi L. Peters, David T. Dicker, Adrian Woolfson, Wafik S. El-Deiry. The IGF1 receptor/insulin receptor dual kinase inhibitor BMS-754807 targets the cancer stem cell population in addition to its synergism with Lapatinib in colorectal cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3998. doi:10.1158/1538-7445.AM2013-3998

Abstract 5565: Circulating tumor cells in the peripheral blood and cerebrospinal fluid of patients with central nervous system metastases

The enumeration of circulating tumor cells in peripheral blood is a validated method of monitoring disease status in patients with epithelial malignancies involving the breast, colon, prostate, or lung. As cancer therapies improve and aim to decrease metastatic burden, the central nervous system (CNS) is emerging as an important sanctuary site for metastasis. Current surveillance and clinical markers of metastatic disease progression involving the CNS are lacking adequate sensitivity, reproducibility, and specificity. One of these clinical markers is cerebrospinal fluid (CSF) cytology, which lacks clarity, is insensitive, requires high sample volumes and is subject to interpretation bias by the pathologist. To overcome these limitations, we previously adapted the Cellsearch system (Veridex) to isolate and enumerate tumor cells in the CSF of breast or non-small cell lung cancer patients with CNS metastases. We recently reported that the number of cells in the CSF directly correlated with the subject9s clinical condition and Karnofsky performance status (KPS) in metastatic breast cancer. Furthermore, imaging of the neuroaxis in these patients revealed disease presence, however, was not indicative of disease burden. A sharp decline in the number of CSF tumor cells (CSFTCs) was universally noted after the onset and maintenance of such ventricular intrathecal chemotherapy. We have continued to follow these patients and have expanded our patient population to include non-small cell lung cancer. This includes a patient that we have followed from a baseline CSFTC count of >10,000 to zero over the course of intrathecal treatment, which as been accompanied by drastically reduced disease by and complete resolution of clinical symptoms. We have also begun to perform concomitant CTC enumeration from peripheral blood in conjunction with CSFTC analysis. Interestingly, while there appears to be no strong correlation between the two subpopulations, tumor cells seemed to be compartmentalized to either the blood or the CSF. Together, the current data indicates that CSFTCs may serve as viable markers for diagnosis and prognostication in the setting of CNS metastases. This novel method of isolating CSFTCs provides a semi-automated platform that greatly increases sensitivity, accuracy and reliability over the standard CSF cytology. Furthermore, this platform enables studies to elucidate the significance and biology of this unique subpopulation of tumor cells, including its relationship with CTCs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5565. doi:1538-7445.AM2012-5565

Abstract 3235: The IGF1 inhibitor BMS-754807 synergizes with Lapatinib in colorectal cancer cell lines

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, ILnnColorectal cancer is the second leading cause of cancer deaths worldwide. Early screening has improved survival rates, but at the time of diagnosis, a significant percentage of patients have advanced disease. Despite improved chemotherapy regimens, the average rate of survival remains less than two years. Drugs that target the epidermal growth factor (EGF) pathway have proven to be beneficial in patients who retain a wild-type KRAS. However 40% of colorectal tumors have a mutated KRAS, and are resistant to EGF-based therapies. One new approach is to target pathways that regulate cancer cell metabolism. The insulin-like growth factor-1 (IGF1) pathway regulates cell growth and motility, activates anti-apoptotic pathways and increases the frequency of cancer stem cells (CSCs). We have previously shown that inhibition of IGF1 signaling with a monoclonal antibody that blocks the IGF1R receptor, inhibited metastasis. In the current study, we examined whether simultaneous inhibition of the IGF1 and EGF pathways would be sufficient to block AKT activation and induce cell death, and also whether the dual targeting of these pathways would increase the cytotoxicity of other anticancer therapies. We report here that the small molecule inhibitor BMS-754807, which blocks the IGF1 and insulin receptors with equal potency, effectively kills a panel of 8 human colorectal cancer cell lines as determined using cell viability assays. The IGF-1R/IR dual inhibitor was found to reduce the size of the cancer stem cell population in several cell lines when measured by side-population analysis. No additional cell death was observed when the IGF1 inhibitor was used in combination with 5-FU and Irinotecan, however, when BMS-754807 was combined with an EGF pathway inhibitor synergy in the induction of cell death was observed in a subset of colorectal cancer cell lines. This effect was seen with the EGFR small molecule inhibitor Lapatinib, but not with the monoclonal antibody Cetuximab. While both Lapatinib and Cetuximab inhibited ERK activation, AKT activation was only inhibited by combination therapy with BMS-754807 and Lapatinib. EGFR activation was, furthermore, inhibited by BMS-754807 alone indicating that there may be cross-talk between the two pathways. We have previously reported that Lapatinib has off target effects in colorectal cancer cell lines, which require higher doses of Lapatinib and induction of DR5 via the JNK pathway. We are currently investigating whether the observed synergy between Lapatinib and BMS-754807 involves off target effects of Lapatinib, although the synergy observed is at doses thought to specifically target the EGFR family. The synergy between BMS-754807 and Lapatinib was observed in cell lines that have mutant BRAF as well as in those with mutant KRAS. This drug combination may consequently provide a new potential treatment strategy for patients who do not derive benefit from current EGFR-based therapies.nnCitation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3235. doi:1538-7445.AM2012-3235

Abstract 2758: Mitomycin C potentiates TRAIL-induced apoptosis through p53-independent upregulation of death receptors: Evidence for the role of C-Jun N-terminal kinase activation

Discovery of the molecular targets of chemotherapeutic medicines and their chemical footprints can validate and improve the use of such medicines. In the present study, we investigated the effect of mitomycin C (MMC), a well-known chemotherapeutic agent on cancer cell apoptosis induced by TRAIL. We found that MMC not only potentiated TRAIL-induced apoptosis in HCT116 (p53-/-) colon cancer cells but also sensitized TRAIL-resistant colon cancer cells HT-29 to the pro-apoptotic cytokine. MMC also improved the pro-apoptotic effects of two TRAIL receptor agonists, the antibodies mapatumumab and lexatumumab. At a mechanistic level, MMC downregulated cell survival proteins including Bcl2, Mcl-1 and Bcl-XL, upregulated cell pro-apoptotic proteins including Bax and Bim, and induced the cell surface expression of TRAIL death receptors DR4 and DR5. Gene silencing of DR5 by short hairpin RNA reduced the apoptosis induced by combination treatment of MMC and TRAIL. Induction of DR4 and DR5 was independent of p53, Bax and Bim, but was dependent on c-Jun N-terminal kinase (JNK) as JNK pharmacologic inhibition and the JNK siRNA abolished the induction of the TRAIL receptors by MMC. The results provide insights into strategies for the development of novel combinatorial cancer therapy combinations that may be further tested in the clinic. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2758. doi:1538-7445.AM2012-2758

Abstract 1400: Mouse models for detection of circulating tumor cells from breast cancer

Breast cancer is the most frequent malignancy among women, causing at least 373,000 deaths per year worldwide, and in United States alone an estimated 208,000 women were diagnosed with breast cancer in 2010. Recent studies indicate that breast cancer is initiated by breast cancer stem cells (BCSCs) that express CD44+/high CD24-/low surface markers. Mammospheres are non-adherent spherical cell clusters grown in selective culture conditions. Our experimental results using mammosphere cultures of different breast cancer cells such as MDA-MB-231 show drastic enrichment of breast cancer stem-like cells with the phenotype of CD44+/high CD24-/low by flow cytometry analysis. We have implanted mammosphere-derived cells into mammary fat pads of nude mice and sampled blood from such tumor-bearing animals to look for the presence of unique breast cancer cells with metastatic potential {circulating tumor cells (CTCs)}, by scoring for Epcam+/cytokeratin+/CD45- tumor cells using the FDA-approved Veridex CellSearch Sysytem. As these metastatic breast cancer cells stably express ZS-Green protein, isolated ZS-Green positive CTCs are being further subjected to breast cancer-specific multiplexed molecular marker analysis. When a mouse with the metastatic breast cancer cell line - 4T1, stained with the CellVue dye is implanted in mammary fat pads, high levels of metastasis are detected with the CellVue marker in different internal organs such as the lungs, liver, heart and lymph nodes. Fluorescence microscopy analysis of blood withdrawn from animals bearing orthotopic 4T1 breast xenograft tumors, could detect ZS-Green positive mouse breast cancer CTCs. These mouse animal models bearing xenograft tumors are facilitating our understanding of CTC detection as well as analysis methods and also in understanding of human breast cancer metastasis. Open questions we are addressing include heterogeneity of CTCs, relationships in stem cell markers and prognostic markers when CTCs are compared with the primary tumors, relationships between tumor burden and tumor aggressiveness with CTC numbers in this mouse model. In addition the model provides an opportunity for testing candidate therapeutic agents and drug combinations. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1400. doi:1538-7445.AM2012-1400

Abstract 3722: Quinacrine and sorafenib combination as potential therapy for anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is uncommon and represents 2-5% of all thyroid cancers. It remains amongst the most lethal human cancers with a reported median survival of 6 months despite therapy. ATC represents over 50% of all thyroid cancer fatalities annually. We have previously shown the effectiveness of quinacrine in combination with standard therapies in hepatocellular and colon carcinoma. Quinacrine has been used in the past to treat lupus and malaria and in addition to being available and affordable (∼30 USD/month of therapy) it has a well-known and acceptable toxicity profile. Here, we evaluate the efficacy of quinacrine in combination with sorafenib on a panel of human anaplastic thyroid cancer tumor cells. We observed that quinacrine as a single agent effectively kills anaplastic thyroid cancer cells in vitro in a concentration-dependent manner as assessed by CellTiter-Glo and sub-G1 analysis. Quinacrine in combination with sorafenib provides an additive effect in vitro. On analyzing, we observe that the anti-apoptotic Bcl-2 family member Mcl-1, which is over-expressed in a number of solid tumors is down-regulated with this combination treatment. Unlike chloroquine that inhibits autophagy, our previous results have not shown that quinacrine9s anti-tumor efficacy involves alterations in autophagy. We are testing the quinacrine plus sorafenib combination in vivo by sub-cutaneous or orthotopic injection in immune-deficient mice of established cell lines as well as freshly isolated cells from patients with anaplastic thyroid cancer. Our findings suggest that quinacrine in combination with sorafenib may be an effective therapeutic strategy for anaplastic thyroid cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3722. doi:1538-7445.AM2012-3722