Cancer drugs with high repositioning potential for Alzheimer's disease

INTRODUCTION

Despite the recent full FDA approval of lecanemab, there is currently no disease modifying therapy (DMT) that can efficiently slow down the progression of Alzheimer's disease (AD) in the general population. This statement emphasizes the need to identify novel DMTs in the shortest time possible to prevent a global epidemic of AD cases as the world population experiences an increase in lifespan.

AREAS COVERED

Here, we review several classes of anti-cancer drugs that have been or are being investigated in Phase II/III clinical trials for AD, including immunomodulatory drugs, RXR agonists, sex hormone therapies, tyrosine kinase inhibitors, and monoclonal antibodies.

EXPERT OPINION

Given the overall course of brain pathologies during the progression of AD, we express a great enthusiasm for the repositioning of anti-cancer drugs as possible AD DMTs. We anticipate an increasing number of combinatorial therapy strategies to tackle AD symptoms and their underlying pathologies. However, we strongly encourage improvements in clinical trial study designs to better assess target engagement and possible efficacy over sufficient periods of drug exposure.

A Multi-Color Flow Cytometric Assay for Quantifying Dinutuximab Binding to Neuroblastoma Cells in Tumor, Bone Marrow, and Blood

GD2, a disialoganglioside, is present on the surface of most neuroblastomas, as well as on some other cancers, such as melanoma and osteogenic sarcoma. The anti-GD2 antibody ch14.18 (dinutuximab) has an FDA-registered indication for use as maintenance therapy for high-risk neuroblastoma with cytokines and 13-cis-retinoic acid after myeloablative therapy. Recent studies using immunohistochemistry of tumor or tumor cells in marrow have shown that some neuroblastomas are negative for GD2. Dinutuximab and other anti-GD2 antibodies are increasingly used in combination with cytotoxic chemotherapy for treating relapsed neuroblastoma, so it is important to be able to identify patients with tumor cells with low GD2 expression, as such patients may experience toxicity but not benefit from the antibody therapy. As the most common clinical samples available for relapsed neuroblastoma are bone marrow aspirates, we developed a method to quantify dinutuximab binding density and the frequency of neuroblastoma cells positive for the antibody in bone marrow aspirates. Here, we describe a multi-color flow cytometry assay that employs non-GD2 antibodies to identify neuroblastoma cells in a mixed population (tumor, bone marrow, or blood) and an anti-GD2 antibody to quantify both the frequency and density of GD2 expression on neuroblastoma cells.

Phase I trial of intravenous fenretinide (4-HPR) plus safingol in advanced malignancies

PURPOSE

Fenretinide (4-HPR) is a synthetic retinoid that induces cytotoxicity through dihydroceramide production. Safingol, a stereochemical-variant dihydroceramide precursor, exhibits synergistic effects when administered with fenretinide in preclinical studies. We conducted a phase 1 dose-escalation clinical trial of this combination.

METHODS

Fenretinide was administered as a 600 mg/m2 24-h infusion on Day 1 of a 21-day cycle followed by 900 mg/m2/day on Days 2 and 3. Safingol was concurrently administered as a 48-h infusion on Day 1 and 2 using 3 + 3 dose escalation. Primary endpoints were safety and maximum tolerated dose (MTD). Secondary endpoints included pharmacokinetics and efficacy.

RESULTS

A total of 16 patients were enrolled (mean age 63 years, 50% female, median three prior lines of therapy), including 15 patients with refractory solid tumors and one with non-Hodgkin lymphoma. The median number of treatment cycles received was 2 (range 2-6). The most common adverse event (AE) was hypertriglyceridemia (88%; 38% ≥ Grade 3), attributed to the fenretinide intralipid infusion vehicle. Other treatment-related AEs occurring in ≥ 20% of patients included anemia, hypocalcemia, hypoalbuminemia, and hyponatremia. At safingol dose 420 mg/m2, one patient had a dose-limiting toxicity of grade 3 troponinemia and grade 4 myocarditis. Due to limited safingol supply, enrollment was halted at this dose level. Fenretinide and safingol pharmacokinetic profiles resembled those observed in monotherapy trials. Best radiographic response was stable disease (n = 2).

CONCLUSION

Combination fenretinide plus safingol commonly causes hypertriglyceridemia and may be associated with cardiac events at higher safingol levels. Minimal activity in refractory solid tumors was observed.

TRIAL REGISTRATION NUMBER

NCT01553071 (3.13.2012).

DNA-PKcs as an upstream mediator of OCT4-induced MYC activation in small cell lung cancer

Small cell lung cancer (SCLC) is a neuroendocrine tumor noted for the rapid development of both metastases and resistance to chemotherapy. High mutation burden, ubiquitous loss of TP53 and RB1, and a mutually exclusive amplification of MYC gene family members contribute to genomic instability and make the development of new targeted agents a challenge. Previously, we reported a novel OCT4-induced MYC transcriptional activation pathway involving c-MYC, pOCT4^S111, and MAPKAPK2 in progressive neuroblastoma, also a neuroendocrine tumor. Using tumor microarray analysis of clinical samples and preclinical models, we now report a correlation in expression between these proteins in SCLC. In correlating c-MYC protein expression with genomic amplification, we determined that some SCLC cell lines exhibited high c-MYC without genomic amplification, implying amplification-independent MYC activation. We then confirmed direct interaction between OCT4 and DNA-PKcs and identified specific OCT4 and DNA-PKcs binding sites. Knock-down of both POU5F1 (encoding OCT4) and PRKDC (encoding DNA-PKcs) resulted in decreased c-MYC expression. Further, we confirmed binding of OCT4 to the promoter/enhancer region of MYC. Together, these data establish the presence of a DNA-PKcs/OCT4/c-MYC pathway in SCLCs. We then disruptively targeted this pathway and demonstrated anticancer activity in SCLC cell lines and xenografts using both DNA-PKcs inhibitors and a protein-protein interaction inhibitor of DNA-PKcs and OCT4. In conclusion, we demonstrate here that DNA-PKcs can mediate high c-MYC expression in SCLCs, and that this pathway may represent a new therapeutic target for SCLCs with high c-MYC expression.

Proposed Mechanism of Long-Term Intraocular Pressure Lowering With the Bimatoprost Implant

Purpose

The purpose of this study was to evaluate the effects of pharmacologically relevant bimatoprost and bimatoprost free acid (BFA) concentrations on matrix metalloproteinase (MMP) gene expression in cells from human aqueous outflow tissues.

Methods

MMP gene expression by human trabecular meshwork (TM), scleral fibroblast (SF), and ciliary muscle (CM) cells exposed to 10 to 1000 µM bimatoprost or 0.1 to 10 µM BFA (intraocular concentrations after intracameral bimatoprost implant and topical bimatoprost dosing, respectively) was measured by polymerase chain reaction array.

Results

Bimatoprost dose-dependently upregulated MMP1 and MMP14 mRNA in all cell types and MMP10 and MMP11 mRNA in TM and CM cells; in TM cells from normal eyes, mean MMP1 mRNA levels were 62.9-fold control levels at 1000 µM bimatoprost. BFA upregulated MMP1 mRNA only in TM and SF cells, to two- to three-fold control levels. The largest changes in extracellular matrix (ECM)-related gene expression by TM cells derived from normal (n = 6) or primary open-angle glaucoma (n = 3) eyes occurred with 1000 µM bimatoprost (statistically significant, ≥50% change for 9-11 of 84 genes on the array, versus 1 gene with 10 µM BFA).

Conclusions

Bimatoprost and BFA had differential effects on MMP/ECM gene expression. Dramatic upregulation in MMP1 and downregulation of fibronectin, which occurred only with bimatoprost at high concentrations observed in bimatoprost implant-treated eyes, may promote sustained outflow tissue remodeling and long-term intraocular pressure reduction beyond the duration of intraocular drug bioavailability. Variability in bimatoprost-stimulated MMP upregulation among cell strains from different donors may help explain differential long-term responses of patients to bimatoprost implant.

Novel insight into the role of clusterin on intraocular pressure regulation by modifying actin polymerization and extracellular matrix remodeling in the trabecular meshwork

This study provides comprehensive mechanistic evidence for the role of clusterin, a stress-response secretory chaperone protein, in the modulation of intraocular pressure (IOP) by regulating the trabecular meshwork (TM) actin cytoskeleton and the extracellular matrix (ECM). The pathological stressors on TM known to elevate IOP significantly lowered clusterin protein levels indicating stress-related clusterin function loss. Small interfering RNA-mediated clusterin loss in human TM cells in vitro induced actin polymerization and stabilization via protein kinase D1, serine/threonine-protein kinase N2 (PRK2), and LIM kinase 1 (LIMK1), and the recruitment and activation of adhesome proteins including paxillin, vinculin, and integrin αV and β5. A complete loss of clusterin as seen in clusterin knockout mice (Clu-/- ) led to significant IOP elevation at postnatal Day 70. Contrarily, constitutive clusterin expression using adenovirus (AdCLU) in HTM cells resulted in the loss of actin polymerization via decreased PRK2, and LIMK1 and negative regulation of integrin αV and β5. Furthermore, we found that AdCLU treatment in HTM cells significantly decreased the ECM protein expression and distribution by significantly increasing matrix metalloprotease 2 (MMP2) activity and lowering the levels of pro-fibrotic proteins such as transforming growth factor-β2 (TGFβ2), thrombospondin-1 (TSP-1), and plasminogen activator inhibitor-1 (PAI-1). Finally, we found that HTM cells supplemented with recombinant human clusterin attenuated the pro-fibrotic effects of TGFβ2. For the first time this study demonstrates the importance of clusterin in the regulation of TM actin cytoskeleton - ECM interactions and the maintenance of IOP, thus making clusterin an interesting target to reverse elevated IOP.

Abstract 5367: DNA-PKcs inhibitors impair OCT4-mediated MYC transcriptional activation in small cell lung cancer

Small cell lung cancer (SCLC) is a disease found almost exclusively in smokers and is a highly aggressive cancer with incredibly poor outcomes. Initially, most patients diagnosed with SCLC respond to platinum + etoposide (PE)-based therapy, but relapse occurs in nearly all patients and is fatal. SCLC is a cancer with a heavy mutational burden, and loss-of-function mutations of the tumor suppressor genes RB1 and TP53 are nearly ubiquitous in SCLC tumors. Amplification and overexpression of the MYC of oncogene occurs in a subset of SCLC tumors that are associated with tumor progression, treatment resistance, and poor outcomes, therefore we pursued the inhibition of the MYC activation. The purpose of this study is to inhibit a novel pathway of MYC transcriptional activation via DNA-PKcs-mediated phosphorylation of OCT4 at its Ser93 residue in SCLC, a MYC transcriptional activation pathway that we discovered. We identified OCT4 being a transcription factor that primarily induce MYC activation. Subsequently, Serine 93 residue of OCT4, a new OCT-4 binding site, was phosphorylated by DNA-PKcs that was a critical step for OCT4-induced MYC activation. In a panel of 19 small cell lung cancer, DNA-PKcs, phosphorylation of OCT4 at Ser93, and c-MYC were positively correlated. We confirmed the binding of DNA-PKcs to OCT4 and identified novel OCT4-binding sites in the MYC promoter/enhancer region that regulated MYC expression via phosphorylation by DNA-PKcs, and DNA-PKcs or OCT4 knockdown decreased c-MYC expression. DNA-PKcs inhibitors also reduced phosphorylation of OCT4 at Ser93 leading to decreases in c-MYC and showed cytotoxic effects via inducing apoptosis by DNA-PKcs inhibitors. DNA-PKcs inhibitors augments antitumor activity of Bcl-2 inhibitors cell lines and xenograft models of small cell lung cancer. In conclusion, report here that DNA-PKcs-mediated phosphorylation of OCT4 at Ser93 is a novel mechanism for activating the MYC oncogene in SCLC, and that DNA-PKcs is a viable target to decrease c-MYC expression in these highly aggressive tumors.

Citation Format: Inhyoung Yang, Ismail Mohiuddin, Sung-Jen Wei, Martinez Gloria, Min H. Kang. DNA-PKcs inhibitors impair OCT4-mediated MYC transcriptional activation in small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5367.

Tumor-Associated Macrophages as Multifaceted Regulators of Breast Tumor Growth

Breast cancer is the most commonly occurring cancer in women of Western countries and is the leading cause of cancer-related mortality. The breast tumor microenvironment contains immune cells, fibroblasts, adipocytes, mesenchymal stem cells, and extracellular matrix. Among these cells, macrophages or tumor-associated macrophages (TAMs) are the major components of the breast cancer microenvironment. TAMs facilitate metastasis of the breast tumor and are responsible for poor clinical outcomes. High TAM density was also found liable for the poor prognosis of breast cancer. These observations make altering TAM function a potential therapeutic target to treat breast cancer. The present review summarizes the origin of TAMs, mechanisms of macrophage recruitment and polarization in the tumor, and the contributions of TAMs in tumor progression. We have also discussed our current knowledge about TAM-targeted therapies and the roles of miRNAs and exosomes in re-educating TAM function.

PPE decontamination to overcome PPE shortage in rural area during pandemic

Despite remarkable developments in healthcare, the world was not ready to stop the spread of the novel COVID-19 pandemic almost a century after the great influenza pandemic. The explosive increase in the number of patients stalled the healthcare system, and the first and apparent issue was the shortage of personal protective equipment (PPE). Our group established a system using a hydrogen peroxide vaporization method to decontaminate and reuse N95 respirators for healthcare workers. The system decontaminated over 12,000 units of PPE to cover institutions in West Texas. This service provided support at the most needed time during the pandemic.

Development of cell-based high throughput luminescence assay for drug discovery in inhibiting OCT4/DNA-PKcs and OCT4-MK2 interactions

Amplification-independent c-MYC overexpression is suggested in multiple cancers. Targeting c-MYC activity has therapeutic potential, but efforts thus far have been mostly unsuccessful. To find a druggable target to modulate c-MYC activity in cancer, we identified two kinases, MAPKAPK2 (MK2) and the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), which phosphorylate the Ser111 and the Ser93 residues of OCT4, respectively, to transcriptionally activate c-MYC. Using these observations, we present here a novel cell-based luminescence assay to identify compounds that inhibit the interaction between these kinases and OCT4. After screening approximately 80,000 compounds, we identified 56 compounds ("hits") that inhibited the luminescence reaction between DNA-PKcs and OCT4, and 65 hits inhibiting the MK2-OCT4 interaction. Using custom antibodies specific for pOCT4^S93 and pOCT4^S111 , the "hits" were validated for their effect on OCT4 phosphorylation and activation. Using a two-step method for validation, we identified two candidate compounds from the DNA-PKcs assay and three from the MK2 assay. All five compounds demonstrate a significant ability to kill cancer cells in the nanomolar range. In conclusion, we developed a cell-based luminescence assay to identify novel inhibitors targeting c-MYC transcriptional activation, and have found five compounds that may function as lead compounds for further development.

Mithramycin induces promoter reprogramming and differentiation of rhabdoid tumor

Rhabdoid tumor (RT) is a pediatric cancer characterized by the inactivation of SMARCB1, a subunit of the SWI/SNF chromatin remodeling complex. Although this deletion is the known oncogenic driver, there are limited effective therapeutic options for these patients. Here we use unbiased screening of cell line panels to identify a heightened sensitivity of rhabdoid tumor to mithramycin and the second-generation analogue EC8042. The sensitivity of MMA and EC8042 was superior to traditional DNA damaging agents and linked to the causative mutation of the tumor, SMARCB1 deletion. Mithramycin blocks SMARCB1-deficient SWI/SNF activity and displaces the complex from chromatin to cause an increase in H3K27me3. This triggers chromatin remodeling and enrichment of H3K27ac at chromHMM-defined promoters to restore cellular differentiation. These effects occurred at concentrations not associated with DNA damage and were not due to global chromatin remodeling or widespread gene expression changes. Importantly, a single 3-day infusion of EC8042 caused dramatic regressions of RT xenografts, recapitulated the increase in H3K27me3, and cellular differentiation described in vitro to completely cure three out of eight mice.

A phase I study of intravenous fenretinide (4-HPR) for patients with malignant solid tumors

BACKGROUND

Fenretinide is a synthetic retinoid that can induce cytotoxicity by several mechanisms. Achieving effective systemic exposure with oral formulations has been challenging. An intravenous lipid emulsion fenretinide formulation was developed to overcome this barrier. We conducted a study to establish the maximum tolerated dose (MTD), preliminary efficacy, and pharmacokinetics of intravenous lipid emulsion fenretinide in patients with advanced solid tumors.

METHODS

Twenty-three patients with advanced solid tumors refractory to standard treatments received fenretinide as a continuous infusion for five consecutive days in 21-day cycles. Five different dose cohorts were evaluated between doses of 905 mg/m² and 1414 mg/m² per day using a 3 + 3 dose escalation design. A priming dose of 600 mg/m² on day 1 was introduced in an attempt to address the asymptomatic serum triglyceride elevations related to the lipid emulsion.

RESULTS

The treatment-related adverse events occurring in ≥ 20% of patients were anemia, hypertriglyceridemia, fatigue, aspartate aminotransferase (AST)/alanine aminotransferase (ALT) increase, thrombocytopenia, bilirubin increase, and dry skin. Five evaluable patients had stable disease as best response, and no patients had objective responses. Plasma steady-state concentrations of the active metabolite were significantly higher than with previous capsule formulations.

CONCLUSION

Fenretinide emulsion intravenous infusion had a manageable safety profile and achieved higher plasma steady-state concentrations of the active metabolite compared to previous capsule formulations. Single-agent activity was minimal but combinatorial approaches are under evaluation.

Abstract 1293: MYC transcription activation mediated by OCT4 as a mechanism of resistance to 13-cisRA-mediated differentiation in neuroblastoma

MYCN genomic amplification is one of the risk factors in neuroblastoma. 13-cis retinoic acid (13-cisRA), a differentiating agent, down-regulates MYCN protein and is part of neuroblastoma maintenance therapy. Despite the improvement in clinical outcome with 13-cisRA, anti-GD2 monoclonal antibody plus cytokine immunotherapy given in first response ~40% of high-risk neuroblastoma patients still die of recurrent disease. Although MYC genomic amplification is rare in neuroblastoma (~1%), 11% of neuroblastoma primary tumors collected at diagnosis (Dx) have high c-MYC protein suggesting that MYC transcriptional activation rather than its gene amplification drives such tumors. Here, we sought to investigate the role of MYC oncogene in progressive disease (PD) and to molecularly characterize mechanisms of MYC expression in neuroblastoma. We report transcriptional activation of MYC medicated by the OCT4 (encoded by POU5F1), functionally replacing MYCN in 13-cisRA-resistant progressive disease neuroblastoma. In large panels of neuroblastoma patient-derived cell lines (19 Dx and 16 PD) and patient-derived xenograft PDX models (8 Dx and 9 PD), we confirmed that c-MYC expression levels were higher in PD relative to Dx lines (P = 0.0005). We identified OCT4 and TCF3 as transcription factors highly expressed in neuroblastoma cells with high c-MYC. Subsequently, we confirmed two novel OCT4-binding sites (including OBS1 and OBS2) located in the MYC promoter/enhancer region: -1209 to -1140 and found that OCT4 NH2-terminal domain (NTD) and POU specific domain (POUs) are critical for MYC transcriptional activation. To identify kinases that is associated with OCT4-induced c-MYC activation, we used mass spectrometry and PhosphoMotif Finder® and identified MAPKAPK2 (MK2) as one of the upstream kinases that can bind to and directly regulate the OCT4 biological function by phosphorylation at its amino acid Ser111 residue to transcriptionally activate MYC expression. The data in 175 MYCN non-amplified high-risk primary tumors (TARGET database) showed that MAPKAPK2 positively correlated with MYC expression (P < 0.001) and overall survival was lower (P < 0.001) for patients with high MAPKAPK2. Also, OCT4, MK2, and c-MYC were higher in PD relative to Dx neuroblastomas models. Functional studies by gene knockdown of the POU5F1 or MAPKAPK2 using shRNAs showed decreased c-MYC expression, inhibition of cell proliferation, and restoring neurite outgrowth in response to 13-cisRA. In conclusion, high c-MYC independent of genomic amplification, not MYCN amplification, is associated with disease progression in neuroblastoma. The MK2-mediated OCT4 transcriptional activation is a novel mechanism for MYC activation in PD neuroblastoma and provides a potential novel therapeutic target.

Citation Format: Sung Jen Wei, Thinh H. Nguyen, Dustin G. Mook, Monish R. Makena, Dattesh Verlekar, Ashly Hindle, Gloria Martinez, Shengping Yang, Hiroyuki Shimada, C. Patrick Reynolds, Min H. Kang. MYC transcription activation mediated by OCT4 as a mechanism of resistance to 13-cisRA-mediated differentiation in neuroblastoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1293.

Abstract 4040: A cell-based screening assay to identify novel kinase inhibitors

The majority of the FDA-approved kinase inhibitors target ATP binding sites of kinases. Despite their activity against tumorigenesis, these therapies are often non-specific and are susceptible to resistance mechanisms. One method of enhancing the selectivity of these compounds and overcoming potential chemoresistance is to better identify novel compounds that are highly specific. In this study, we introduce one such strategy by identifying kinase inhibitors that target kinase-substrate interactions. c-MYC overexpression and deregulation has been implicated in the development and progression of a number of malignancies. We have previously identified that OCT4 binds to the MYC promoter/enhancer region to transcriptionally activate c-MYC. Novel OCT4 binding sites in the c-MYC promoter region were identified, and kinases (DNA-PKcs for the current study) that mediate the phosphorylation of specific amino acid residues of OCT4 were determined. We then identified the domains of DNA-PKcs that are critical to bind and phosphorylate OCT4. The goal of the current project is to develop an assay to identify the compounds that interferes the interaction between OCT4 and DNA-PKcs and to validate the identified "hits." In order to selectively inhibit the interaction of protein-kinase related to c-MYC transcriptional activation, we co-expressed the fragments of OCT4 required for c-MYC expression and the fragments DNA-PKcs required to activate OCT4 to 1) confirm the interaction between DNA-PKcs and OCT4, and 2) develop a cell-based assay that can screen novel compounds that prevent this interaction. After confirming the kinase-substrate interaction, we co-transduced the crucial fragments of DNA-PKcs and OCT4 tagged with luminescent probes in HEK 293FT cells. We then screened a chemical library of compounds to identify hits that inhibited luminescence, and thus our kinase-substrate protein interaction. In our screening assay, 67 compounds were found to inhibit the luminescence interaction between the tagged OCT4 and DNA-PKcs protein fragments. After the initial screening, we conducted a two-step hit validation for the 67 hits identified that consisted of: 1) the decrease in pOCT4S93 expression along with the reduction in c-MYC expression: 2) and the inhibition of binding between DNA-PKcs and OCT4 by co-immunoprecipitation. Additional experiments to validate the hits include kinase activity assays and immunoblotting to determine if the screened hits inhibited DNA-PKcs kinase activity. In conclusion, our screening assay and validation experiments identified 7 novel compounds that demonstrated: 1) impairment of DNA-PKcs-mediated phosphorylation of OCT4; and 2) inhibition of the DNA-PKcs-OCT4 kinase-substrate interaction. These newly identified compounds have the potential to oppose aberrant c-MYC expression and warrant further investigation in order to determine their activity in high c-MYC-expressing malignancies.

Citation Format: Ismail S. Mohiuddin, Sung J. Wei, Inhyoung Yang, Gloria Martinez, Hwangeui Cho, Min H. Kang. A cell-based screening assay to identify novel kinase inhibitors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4040.

Abstract 705: A cell-based screening assay to identify agents interfering protein-protein interaction of MAPKAPK2 and OCT4

c-MYC overexpression plays an important role in tumorigenesis as well as in the progression of tumors. Historically, direct targeting strategies have been challenging due to c-MYC being a transcription factor. Our observation demonstrated that MAPKAPK2 as one of the two major protein kinases involved in binding and phosphorylating OCT4 at serine 111 residue to induce c-MYC activation in progressive disease neuroblastoma. In targeting this novel pathway of c-MYC activation, we considered two options: direct inhibition of MAPKAPK2 or inhibition of MAPKAPK2-OCT4 protein-protein interaction. Given the limitations of direct targeting kinases, namely resistance and off-target effect, we pursued the inhibition of the protein-protein interaction. The purpose of this study is to introduce a novel cell-based assay for compound screening and validation steps to identify compounds that inhibit OCT4-MAPKAPK2 interaction. First, OCT4 (NTD and POUs: the domains critical for c-MYC activation) and MAPKAPK2 were exogenously expressed by a single vector with CMV promoter using a lentiviral vector system in NCI-H82, a small cell lung cancer cell line. Upon the optimization of the assay, we screened approximately 100,000 compounds to identify “hits” by statistically analyzing the reduction in luminescence. Seventy-six compounds were found to inhibit the interaction of MAPKAPK2-OCT4. Subsequently, we have used a two-step hit validation for the 76 compounds: 1) the decrease in pOCT4S111 expression along with the reduction in c-MYC expression by immunoblotting: 2) and the inhibition of binding between MAPKAPK2 and OCT4 by co-immunoprecipitation. The validation step further narrowed down the hits to three compounds that reduced the phosphorylation of OCT4 at S111 and inhibited the MAPKAPK2-OCT4 interaction. To verify the compounds interfering the MAPKAPK2-OCT4 interaction, we used in vitro assay using recombinant human MAPKAPK2 kinase and OCT4 and all three compounds inhibited phosphorylation of OCT4S111. These all compounds also tested minimally affected ATP-dependent MAPKAPK2 kinase relative to the known MAPKAPK2 inhibitor (PF3644022). In conclusion, our screening assay and validation experiments was successfully implemented in identifying hits and the validation step confirmed three novel compounds that demonstrated: 1) impairment of MAPKAPK2-mediated phosphorylation of OCT4; and 2) inhibition of the MAPKAPK2-OCT4 kinase-substrate interaction. These compounds may be further optimized to minimize systemic toxicities and improve the anti-cancer activity for the treatment of neuroblastoma or small cell lung cancer with high c-MYC expression.

Citation Format: Inhyoung Yang, Sung-Jen Wei, Ismail Mohiuddin, Gloria M. Martinez, Min H. Kang. A cell-based screening assay to identify agents interfering protein-protein interaction of MAPKAPK2 and OCT4 [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 705.

TGFβ2-Hepcidin Feed-Forward Loop in the Trabecular Meshwork Implicates Iron in Glaucomatous Pathology

Purpose

Elevated levels of transforming-growth-factor (TGF)-β2 in the trabecular meshwork (TM) and aqueous humor are associated with primary open-angle glaucoma (POAG). The underlying mechanism includes alteration of extracellular matrix homeostasis through Smad-dependent and independent signaling. Smad4, an essential co-Smad, upregulates hepcidin, the master regulator of iron homeostasis. Here, we explored whether TGF-β2 upregulates hepcidin, implicating iron in the pathogenesis of POAG.

Methods

Primary human TM cells and human and bovine ex vivo anterior segment organ cultures were exposed to bioactive TGF-β2, hepcidin, heparin (a hepcidin antagonist), or N-acetyl carnosine (an antioxidant), and the change in the expression of hepcidin, ferroportin, ferritin, and TGF-β2 was evaluated by semiquantitative RT-PCR, Western blotting, and immunohistochemistry. Increase in reactive oxygen species (ROS) was quantified with dihydroethidium, an ROS-sensitive dye.

Results

Primary human TM cells and bovine TM tissue synthesize hepcidin locally, which is upregulated by bioactive TGF-β2. Hepcidin downregulates ferroportin, its downstream target, increasing ferritin and iron-catalyzed ROS. This causes reciprocal upregulation of TGF-β2 at the transcriptional and translational levels. Heparin downregulates hepcidin, and reduces TGF-β2-mediated increase in ferritin and ROS. Notably, both heparin and N-acetyl carnosine reduce TGF-β2-mediated reciprocal upregulation of TGF-β2.

Conclusions

The above observations suggest that TGF-β2 and hepcidin form a self-sustained feed-forward loop through iron-catalyzed ROS. This loop is partially disrupted by a hepcidin antagonist and an anti-oxidant, implicating iron and ROS in TGF-β2-mediated POAG. We propose that modification of currently available hepcidin antagonists for ocular use may prove beneficial for the therapeutic management of TGF-β2-associated POAG.

Antineoplastic Agents Targeting Sphingolipid Pathways

Emerging studies in the enigmatic area of bioactive lipids have made many exciting new discoveries in recent years. Once thought to play a strictly structural role in cellular function, it has since been determined that sphingolipids and their metabolites perform a vast variety of cellular functions beyond what was previously believed. Of utmost importance is their role in cellular signaling, for it is now well understood that select sphingolipids serve as bioactive molecules that play critical roles in both cancer cell death and survival, as well as other cellular responses such as chronic inflammation, protection from intestinal pathogens, and intrinsic protection from intestinal contents, each of which are associated with oncogenesis. Importantly, it has been demonstrated time and time again that many different tumors display dysregulation of sphingolipid metabolism, and the exact profile of said dysregulation has been proven to be useful in determining not only the presence of a tumor, but also the susceptibility to various chemotherapeutic drugs, as well as the metastasizing characteristics of the malignancies. Since these discoveries surfaced it has become apparent that the understanding of sphingolipid metabolism and profile will likely become of great importance in the clinic for both chemotherapy and diagnostics of cancer. The goal of this paper is to provide a comprehensive review of the current state of chemotherapeutic agents that target sphingolipid metabolism that are undergoing clinical trials. Additionally, we will formulate questions involving the use of sphingolipid metabolism as chemotherapeutic targets in need of further research.

MYC transcription activation mediated by OCT4 as a mechanism of resistance to 13-cisRA-mediated differentiation in neuroblastoma

Despite the improvement in clinical outcome with 13-cis-retinoic acid (13-cisRA) + anti-GD2 antibody + cytokine immunotherapy given in first response ~40% of high-risk neuroblastoma patients die of recurrent disease. MYCN genomic amplification is a biomarker of aggressive tumors in the childhood cancer neuroblastoma. MYCN expression is downregulated by 13-cisRA, a differentiating agent that is a component of neuroblastoma therapy. Although MYC amplification is rare in neuroblastoma at diagnosis, we report transcriptional activation of MYC medicated by the transcription factor OCT4, functionally replacing MYCN in 13-cisRA-resistant progressive disease neuroblastoma in large panels of patient-derived cell lines and xenograft models. We identified novel OCT4-binding sites in the MYC promoter/enhancer region that regulated MYC expression via phosphorylation by MAPKAPK2 (MK2). OCT4 phosphorylation at the S111 residue by MK2 was upstream of MYC transcriptional activation. Expression of OCT4, MK2, and c-MYC was higher in progressive disease relative to pre-therapy neuroblastomas and was associated with inferior patient survival. OCT4 or MK2 knockdown decreased c-MYC expression and restored the sensitivity to 13-cisRA. In conclusion, we demonstrated that high c-MYC expression independent of genomic amplification is associated with disease progression in neuroblastoma. MK2-mediated OCT4 transcriptional activation is a novel mechanism for activating the MYC oncogene in progressive disease neuroblastoma that provides a therapeutic target.

Prion protein modulates endothelial to mesenchyme-like transition in trabecular meshwork cells: Implications for primary open angle glaucoma

Endothelial-to-mesenchyme-like transition (Endo-MT) of trabecular meshwork (TM) cells is known to be associated with primary open angle glaucoma (POAG). Here, we investigated whether the prion protein (PrP^C), a neuronal protein known to modulate epithelial-to-mesenchymal transition in a variety of cell types, is expressed in the TM, and plays a similar role at this site. Using a combination of primary human TM cells and human, bovine, and PrP-knock-out (PrP^−/−) mouse models, we demonstrate that PrP^C is expressed in the TM of all three species, including endothelial cells lining the Schlemm’s canal. Silencing of PrP^C in primary human TM cells induces aggregation of β1-integrin and upregulation of α-smooth muscle actin, fibronectin, collagen 1A, vimentin, and laminin, suggestive of transition to a mesenchyme-like phenotype. Remarkably, intraocular pressure is significantly elevated in PrP^−/− mice relative to wild-type controls, suggesting reduced pliability of the extracellular matrix and increased resistance to aqueous outflow in the absence of PrP^C. Since PrP^C is cleaved by members of the disintegrin and matrix-metalloprotease family that are increased in the aqueous humor of POAG arising from a variety of conditions, it is likely that concomitant cleavage of PrP^C exaggerates and confounds the pathology by inducing Endo-MT-like changes in the TM.

DNA-PK as an Emerging Therapeutic Target in Cancer

The DNA-dependent protein kinase (DNA-PK) plays an instrumental role in the overall survival and proliferation of cells. As a member of the phosphatidylinositol 3-kinase-related kinase (PIKK) family, DNA-PK is best known as a mediator of the cellular response to DNA damage. In this context, DNA-PK has emerged as an intriguing therapeutic target in the treatment of a variety of cancers, especially when used in conjunction with genotoxic chemotherapy or ionizing radiation. Beyond the DNA damage response, DNA-PK activity is necessary for multiple cellular functions, including the regulation of transcription, progression of the cell cycle, and in the maintenance of telomeres. Here, we review what is currently known about DNA-PK regarding its structure and established roles in DNA repair. We also discuss its lesser-known functions, the pharmacotherapies inhibiting its function in DNA repair, and its potential as a therapeutic target in a broader context.

Hydrophilic interaction liquid chromatography-tandem mass spectrometric approach for simultaneous determination of safingol and D-erythro-sphinganine in human plasma

A simple and specific hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) method was developed for the simultaneous determination of C18-L-threo-sphinganine (safingol, an anti-neoplastic in phase I trials) and its diastereomer, C18-D-erythro-sphinganine (sphinganine), in human plasma. Sample pretreatment involved a protein precipitation with methanol using 25 μL aliquots of plasma. Chromatographic separation of the diastereomers and C17-D-erythro-sphinganine, an internal standard, was achieved on a Xbridge HILIC (3.5 μm, 100 × 2.1 mm) using isocratic elution with the mobile phase of 2 mM ammonium bicarbonate in water (pH 8.3) and acetonitrile at a flow rate of 0.3 mL/min. Electrospray ionization (ESI) mass spectrometry was operated in the positive ion mode with multiple reaction monitoring (MRM). The calibration curves obtained were linear over the concentration range of 0.2-100 ng/mL with a lower limit of quantification of 0.2 ng/mL. The relative standard deviation of intra-day and inter-day precision was below 8.27%, and the accuracy ranged from 92.23 to 110.06%. The extraction recoveries were found to be higher than 93.22% and IS-normalized matrix effect was higher than 90.92%. The analytes were stable for the durations of the stability studies. The validated method was successfully applied to the analyses of pharmacokinetic samples from patients treated with safingol and all-trans-N-(4-hydroxyphenyl)retinamide; (fenretinide, 4-HPR) in a current phase I clinical trial (SPOC-2010-002, ClinicalTrials.gov Identifier: NCT01553071).

Broad Spectrum Activity of the Checkpoint Kinase 1 Inhibitor Prexasertib as a Single Agent or Chemopotentiator Across a Range of Preclinical Pediatric Tumor Models

PURPOSE

Checkpoint kinase 1 (CHK1) inhibitors potentiate the DNA-damaging effects of cytotoxic therapies and/or promote elevated levels of replication stress, leading to tumor cell death. Prexasertib (LY2606368) is a CHK1 small-molecule inhibitor under clinical evaluation in multiple adult and pediatric cancers. In this study, prexasertib was tested in a large panel of preclinical models of pediatric solid malignancies alone or in combination with chemotherapy.

EXPERIMENTAL DESIGN

DNA damage and changes in cell signaling following in vitro prexasertib treatment in pediatric sarcoma cell lines were analyzed by Western blot and high content imaging. Antitumor activity of prexasertib as a single agent or in combination with different chemotherapies was explored in cell line-derived (CDX) and patient-derived xenograft (PDX) mouse models representing nine different pediatric cancer histologies.

RESULTS

Pediatric sarcoma cell lines were highly sensitive to prexasertib treatment in vitro, resulting in activation of the DNA damage response. Two PDX models of desmoplastic small round cell tumor and one malignant rhabdoid tumor CDX model responded to prexasertib with complete regression. Prexasertib monotherapy also elicited robust responses in mouse models of rhabdomyosarcoma. Concurrent administration with chemotherapy was sufficient to overcome innate resistance or prevent acquired resistance to prexasertib in preclinical models of neuroblastoma, osteosarcoma, and Ewing sarcoma, or alveolar rhabdomyosarcoma, respectively.

CONCLUSIONS

Prexasertib has significant antitumor effects as a monotherapy or in combination with chemotherapy in multiple preclinical models of pediatric cancer. These findings support further investigation of prexasertib in pediatric malignancies.

Cytotoxic activity of difluoromethylornithine compared with fenretinide in neuroblastoma cell lines

BACKGROUND

Maintenance therapy with 13-cis-retinoic acid and immunotherapy (given after completion of intensive cytotoxic therapy) improves outcome for high-risk neuroblastoma patients. The synthetic retinoid fenretinide (4-HPR) achieved multiple complete responses in relapse/refractory neuroblastoma in early-phase clinical trials, has low systemic toxicity, and has been considered for maintenance therapy clinical trials. Difluoromethylornithine (DFMO, an irreversible inhibitor of ornithine decarboxylase with minimal single-agent clinical response data) is being used for maintenance therapy of neuroblastoma. We evaluated the cytotoxic activity of DFMO and fenretinide in neuroblastoma cell lines.

PROCEDURE

We tested 16 neuroblastoma cell lines in bone marrow-level hypoxia (5% O₂ ) using the DIMSCAN cytotoxicity assay. Polyamines were measured by HPLC-mass spectrometry and apoptosis by transferase dUTP nick end labeling (TUNEL) using flow cytometry.

RESULTS

At clinically achievable levels (100 μM), DFMO significantly decreased (P < 0.05) polyamine putrescine and achieved modest cytotoxicity (<1 log (90% cytotoxicity). Prolonged exposures (7 days) or culture in 2% and 20% O₂ did not enhance DFMO cytotoxicity. However, fenretinide (10 μM) even at a concentration lower than clinically achievable in neuroblastoma patients (20 μM) induced ≥ 1 log cell kill in 14 cell lines. The average IC₉₀ and IC₉₉ of fenretinide was 4.7 ± 1 μM and 9.9 ± 1.8 μM, respectively. DFMO did not induce a significant increase (P > 0.05) in apoptosis (TUNEL assay). Apoptosis by fenretinide was significantly higher (P < 0.001) compared with DFMO or controls.

CONCLUSIONS

DFMO as a single agent has minimal cytotoxic activity for neuroblastoma cell lines.

Ceramide synthase-6 confers resistance to chemotherapy by binding to CD95/Fas in T-cell acute lymphoblastic leukemia

Ceramide synthases (CERS) produce ceramides which are key intermediators in the biosynthesis of complex sphingolipids and play an important role in cell proliferation, differentiation, apoptosis and senescence. CERS6 is an isoform of ceramide synthases known to generate ceramides with C16 acyl chain (C₁₆-Cer). CERS6 and C₁₆-Cer levels were significantly higher in acute lymphoblastic leukemia (ALL) cells in comparison to peripheral blood mononuclear cells and T lymphocytes derived from healthy human volunteers. We investigated the role of CERS6 in chemo-resistance in T-ALL cell lines. Stable knockdown of CERS6 in CCRF-CEM and MOLT-4 cells resulted in increased sensitivity to ABT-737, a pan-BCL-2 inhibitor, while CCRF-CEM cells with exogenous CERS6 expression showed resistance to ABT-737 relative to the vector control. The cytotoxic activity of ABT-737 in CERS6 knockdown cells was significantly reduced by the addition of a caspase-8 inhibitor Z-IETD, suggesting that CERS6 alters the cytotoxicity via extrinsic pathway of apoptosis. By co-immunoprecipitation of CERS6 in CCRF-CEM cells, we identified CD95/Fas, a mediator of extrinsic apoptotic pathway, as a novel CERS6 binding partner. In Fas pull-down samples, FADD (Fas-associated protein with death domain) was detected at higher levels in cells with CERS6 knockdown compared with control cells when treated with ABT-737, and this was reversed by the overexpression of CERS6, demonstrating that CERS6 interferes with Fas–FADD DISC assembly. CERS6 may serve as a biomarker in determining the effectiveness of anticancer agents acting via the extrinsic pathway in T-ALL.

Microvascular Density Is Associated With Retinal Ganglion Cell Axonal Volume in the Laminar Compartments of the Human Optic Nerve Head

Purpose

To quantify associations between microvascular density and retinal ganglion cell (RGC) axonal volume in the laminar compartments of the human optic nerve head (ONH).

Methods

Eleven normal human ONHs were evaluated. Antibodies were used to label the vascular endothelium (factor VIII-related antigen/von Willebrand factor antibody) and RGC axons (neurofilament heavy antibody). Three-dimensional analysis of confocal scanning laser microscope images was used to study microvascular density and RGC axonal volume in the prelaminar, anterior lamina cribrosa, posterior lamina cribrosa, and retrolaminar compartments.

Results

Microvascular volume was significantly different between laminar compartments (P < 0.0083) and was greatest in the prelaminar region, occupying 11.7% of tissue volume. Microvascular volume per RGC axonal volume and cumulative capillary length per RGC axonal volume were significantly different between laminar compartments (all P < 0.0083). Both were significantly greater in the posterior laminar cribrosa (27.4% and 2.28 × 10-3 μm/μm3, respectively).

Conclusions

Microvascular density is closely coupled to RGC axonal volume in the ONH. The posterior laminar cribrosa is a site of high blood supply as evidenced by a greater ratio of microvascular density to RGC axonal volume. The greater percentage of tissue volume occupied by microvasculature in the prelaminar region may implicate it as a site where significant connections between the central retinal artery and short posterior ciliary arteries occur.

Abstract 4812: Vorinostat and fenretinide synergize in preclinical models of T-cell lymphoid malignancies via reactive oxygen species

Introduction: T-cell lymphoid malignancies (TCLMs) are in need of novel and more effective therapies. Pan-histone deacetylase (HDAC) inhibitors vorinostat and belinostat, and class I specific HDAC inhibitor romidepsin have achieved FDA registration as 2nd line therapies for peripheral and/or cutaneous T-cell lymphomas. The cytotoxic retinoid fenretinide achieved durable complete responses against T-cell lymphomas in early-phase clinical trials and T-cell lymphoma patients who failed prior HDAC inhibitor treatment responded to fenretinide (Clinical Cancer Res 23:4550-4555, 2017). Fenretinide is currently being evaluated in a Phase IIa clinical trial for relapsed/refractory PTCL patients (NCT02495415). We have previously shown romidepsin and fenretinide synergize in preclinical models of T-cell lymphoid malignancies (Molecular Cancer Therapeutics 16:649-661, 2017). There exist some key differences in the activity of various classes of HDAC's, which have significantly different chemical structures and metabolic profiles. Therefore we determined if the pan-HDAC inhibitor vorinostat synergizes with fenretinide.

Methods and Results: Using the DIMSCAN cytotoxicity assay, we demonstrated cytotoxic synergy between vorinostat and fenretinide in nine TCLM cell lines at clinically-achievable concentrations that lacked cytotoxicity for non-malignant cells (fibroblasts and blood mononuclear cells). In vivo, vorinostat + fenretinide + ketoconazole (enhances fenretinide exposures by inhibiting fenretinide metabolism) showed greater activity in subcutaneous (COG-LL-317m and TX-LY-183x PDX) TCLM xenograft models than single agent vorinostat or fenretinide + ketoconazole. Fenretinide + vorinostat caused a reactive oxygen species (ROS, measured by DCFDA dye)-dependent increase in apoptosis (via TUNEL assay), and histone acetylation (measured by immunoblotting). The synergistic cytotoxicity, apoptosis, and histone acetylation of fenretinide + vorinostat was abrogated by antioxidant vitamin C. Vorinostat + fenretinide activated p38 and JNK via ROS, and shRNA knockdown of p38 and JNK1 significantly decreased the synergistic cytotoxicity and apoptosis. Vorinostat + fenretinide also showed synergistic cytotoxicity for six B-lymphoid malignancy cell lines.

Conclusion: Like romidepsin, vorinostat combined with fenretinide achieved synergistic activity in preclinical models of TCLMs, but not in non-malignant cells, via a novel molecular mechanism. As vorinostat is an oral agent and not a PGP substrate it may have advantages in such combination therapy. These data support conducting a clinical trial of vorinostat combined with fenretinide in relapsed and refractory TCLMs.

Citation Format: Monish Ram Makena, Thinh H. Nguyen, Balakrishna Koneru, Ashly Hindle, Wan-Hsi Chen, Dattesh U. Verlekar, Min H. Kang, C. Patrick Reynolds. Vorinostat and fenretinide synergize in preclinical models of T-cell lymphoid malignancies via reactive oxygen species [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4812.

Phase I study of vorinostat in combination with isotretinoin in patients with refractory/recurrent neuroblastoma: A new approaches to Neuroblastoma Therapy (NANT) trial

BACKGROUND

Vorinostat combined with retinoids produces additive antitumor effects in preclinical studies of neuroblastoma. Higher systemic exposures of vorinostat than achieved in pediatric phase I trials with continuous daily dosing are necessary for in vivo increased histone acetylation and cytotoxic activity. We conducted a phase I trial in children with relapsed/refractory neuroblastoma to determine the maximum tolerated dose (MTD) of vorinostat on an interrupted schedule, escalating beyond the previously identified pediatric MTD.

METHODS

Isotretinoin (cis-13-retinoic acid) 80 mg/m² /dose was administered by mouth twice daily on days 1-14 in combination with escalating doses of daily vorinostat up to 430 mg/m² /dose (days 1-4; 8-11) in each 28-day cycle using the standard 3 + 3 design. Vorinostat pharmacokinetic testing and histone acetylation assays were performed.

RESULTS

Twenty-nine patients with refractory or relapsed neuroblastoma were enrolled and 28 were evaluable for dose escalation decisions. Median number of cycles completed was two (range 1-15); 11 patients received four or more cycles. Three patients experienced cycle 1 dose-limiting toxicities. A total of 18 patients experienced grade 3/4 toxicities related to study therapy. The maximum intended dose of vorinostat (430 mg/m² /day, days 1-4; 8-11) was tolerable and led to increased histone acetylation in surrogate tissues when compared to lower doses of vorinostat (P = 0.009). No objective responses were seen.

CONCLUSIONS

Increased dose vorinostat (430 mg/m² /day) on an interrupted schedule is tolerable in combination with isotretinoin. This dose led to increased vorinostat exposures and demonstrated increased histone acetylation. Prolonged stable disease in patients with minimal residual disease warrants further investigation.

Abstract 5841: Ceramide synthase-6 binding to CD95/Fas confers resistance to chemotherapy in T-cell acute lymphoblastic leukemia cells

Ceramide synthase (CERS) produces ceramides, key intermediators in the biosynthesis of complex sphingolipids and play an important role in cell growth, differentiation, apoptosis, and senescence. Six isoforms of ceramide synthases (CERS1-6) with varying substrate specificity generate ceramides of diverse chain lengths. In normal tissues, CERS2, synthesizing ceramides with C24 acyl chain (C24-Cer), is highly expressed in most of the tissues while CerS6 generates C16-Cer with low and tissue-specific distribution. Our data showed that CERS6 and C16-Cer levels were significantly higher in acute lymphoblastic leukemia (ALL) cells in comparison to peripheral blood mononuclear cells and T-Lymphocytes derived from healthy human volunteers. The purpose of this study was to investigate the role of CERS6 in chemo resistance in T-ALL models. Stable knockdown/overexpression of CERS6 was achieved by lentiviral vector transduction. Ceramide levels were measured by LC/MS. Cytotoxicity of conventional and investigational anti-leukemia agents was evaluated in T- ALL cells with altered CERS6 levels using DIMSCAN assay. CERS6 knockdown significantly decreased C16-Cer by 4-fold (p&lt;0.01) while CERS6 overexpression increased C16-Cer by 2-fold (p&lt;0.05). CERS6 knockdown in CCRF-CEM cells increased their sensitivity to a pan BCL-2 inhibitor, ABT-737 as well as a glucocorticoid, dexamethasone (DXM). The percent survival of CCRF-CEM cells with CERS6 knockdown treated with ABT-737 (100nM) or DXM (100nM) was 5% and 2% at 72h while cells transduced with non-targeting shRNA showed survival of 87% and 33% (p&lt;0.001). In CCRF-CEM cells with CERS6 overexpression, the percent survival, when treated with ABT-737 (300nM) or DXM (300nM) for 72h, was significantly higher relative to the cells transduced with vector control: 39% vs 2% for ABT-737 and 33% vs 0.4% for DXM, p&lt;0.01. Higher cleavage of PARP, Caspase 3 and Caspase 8 was seen in ABT-737 or DXM treated cells with CERS6 knockdown, which was reversed by the overexpression of CERS6. Sensitivity to ABT-737 in CERS6 knockdown cells was significantly reduced by a Caspase 8 inhibitor, suggesting that CERS6 alters ALL cell sensitivity to chemotherapy via extrinsic pathway of apoptosis. Pull down of CERS6 in CCRF-CEM cells identified CD95/Fas, a death receptor leading to activation of extrinsic apoptotic pathway, as a CERS6 binding partner. In CERS6 knockdown cells, a higher level of FADD was detected in Fas pull-down samples when treated with ABT-737 compared with cells transduced with non-targeting shRNA, indicating CERS6 interferes Fas/FADD assembly in inducing apoptosis. Taken together, CERS6 modulation affected the sensitivity of T-ALL cells to chemotherapy by interfering with Fas/FADD assembly in extrinsic apoptotic pathway. CERS6 may serve as a biomarker in determining the efficacy of anticancer drugs acting via extrinsic apoptotic pathway in T-ALL.

Citation Format: Dattesh U. Verlekar, Hwangeui Cho, Sung-Jen Wei, Min H. Kang. Ceramide synthase-6 binding to CD95/Fas confers resistance to chemotherapy in T-cell acute lymphoblastic leukemia cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5841.

Effects of Keratinocyte-Derived Cytokine (CXCL-1) on the Development of Theiler's Virus-Induced Demyelinating Disease

CXCL-1, also called keratinocyte-derived cytokine (KC), is a predominant chemokine produced in glial cells upon infection with Theiler's murine encephalomyelitis virus (TMEV). In this study, we assessed the role of KC in the development of TMEV-induced demyelinating disease by utilizing polyclonal anti-KC antibodies as well as KC-expressing recombinant TMEV. Our results indicate that the level of KC produced after infection with TMEV or stimulation with various TLRs is significantly higher in various cells from susceptible SJL mice compared to those in cells from resistant B6 mice. SJL mice treated with rabbit anti-KC antibodies displayed accelerated development of TMEV-induced demyelinating disease, elevated viral loads in the CNS and decreased antiviral T cell responses. In addition, infection of susceptible SJL mice with recombinant KC-TMEV produced biologically active KC, which resulted in the accelerated pathogenesis of demyelinating disease and elevated T cell responses to viral antigens compared to mice infected with control recombinant HEL-TMEV. These results strongly suggest that both the lack of KC during TMEV infection and the excessive presence of the chemokine promote the pathogenesis of demyelinating disease. Therefore, a balance in the level of KC during TMEV infection appears to be critically important in controlling the pathogenesis of demyelinating disease.

Abstract CT146: Plasma pharmacokinetics of liposomal irinotecan (nal-IRI) in pediatric oncology patients with recurrent or refractory solid tumors: South Plains Oncology Consortium Study 2012-001

Background/Objectives: Children with relapsed or refractory solid tumors have a poor prognosis. Irinotecan is active in some pediatric solid tumors and synergizes with alkylating agents. nal-IRI encapsulates irinotecan into long-circulating, liposome-based nanoparticles. In adults, nal-IRI demonstrated extended plasma exposure compared with non-liposomal irinotecan. In pediatric solid tumor models, nal-IRI had robust preclinical activity and synergized with cyclophosphamide, and therefore merits testing in children with relapsed and refractory solid tumors. Herein we describe a phase 1 dose-escalation study of nal-IRI in combination with cyclophosphamide (NCT02013336) and preliminary pharmacokinetic and safety results.

Methods: Cyclophosphamide was administered on days 1-5 of each cycle (250 mg/m2/d intravenously [IV]) with a single 90-min IV infusion of nal-IRI on day 3 of a Q3-week schedule, escalating from 60 mg/m2 to 210 mg/m2 (expressed as irinotecan HCL trihydrate salt), in a standard 3+3 dose-escalation design to determine the maximum tolerated dose. To date, the nal-IRI dose has been escalated from 60 mg/m2 to 150 mg/m2. Samples for pharmacokinetic analysis were collected during the first cycle of chemotherapy before infusion and at 4h, 24h, 48h, 120h, and 168h post-infusion. Plasma pharmacokinetics of total irinotecan and SN-38 were quantified using mixed effect modeling, and were compared with adult values from a population pharmacokinetic analysis of 6 clinical studies of nal-IRI.1

Results: To date, 10 males and 6 females with a median age of 12.8 years (range: 5-19) have been enrolled: 10 with Ewing sarcoma, 2 with neuroblastoma, 3 with osteosarcoma, and 1 with rhabdomyosarcoma. The estimated total irinotecan volume of distribution (Vd) was 1.9 L, clearance (CL) was 10.3 L/week, and half-life (t1/2) was 21.2 h, which were 42% (Vd and CL) of adult values and comparable to adult values (t1/2). The corresponding Cmax was 72% higher than that observed in adults. SN-38 clearance was 11.4 L/week (comparable to adults), t1/2 was 19.3 h (48% of adult values), and Cmax was 68% of adult values. Thrombocytopenia leading to treatment delay was a dose-limiting toxicity at 150 mg/m2 (n=1); other systemic toxicity attributed to chemotherapy within the 1st cycle was nausea/vomiting (n=1).

Conclusions: Preliminary safety and pharmacokinetic data support continued investigation of nal-IRI in pediatric oncology. Clinical outcomes including safety of patients treated in this study will be reported once a maximum tolerated dose is achieved.

1. Adiwijaya B et al. Clin Pharmacol Ther. 2017. In press.

Citation Format: Paul D. Harker-Murray, William H. Meyer, Patrick Leavey, Min H. Kang, Hwangeui Cho, Bambang S. Adiwijaya, Jonathan B. Fitzgerald, J Marc Pipas, Daryl C. Drummond, C. Patrick Reynolds. Plasma pharmacokinetics of liposomal irinotecan (nal-IRI) in pediatric oncology patients with recurrent or refractory solid tumors: South Plains Oncology Consortium Study 2012-001 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT146. doi:10.1158/1538-7445.AM2017-CT146

Abstract LB-049: Low plasma levels of 13-cis-retinoic acid (isotretinoin) and its active metabolite 4-oxo-13-cis-retinoic acid are associated with lower overall survival of high-risk neuroblastoma patients

Background and purpose: Isotretinoin (13-cis-retinoic acid; 13-cisRA), a differentiation inducer, improves outcome for high-risk neuroblastoma when given after myeloablative therapy. Published pharmacokinetic (PK) studies suggested that many patients achieve 13-cisRA levels lower than 5 μM (effective against neuroblastoma in vitro) and that 4-oxo-13-cisRA is an active metabolite of 13-cisRA. We assessed the pharmacokinetics (PK) of 13-cisRA and 4-oxo-13-cisRA and their relation to treatment outcome in Children’s Oncology Group (COG) phase III studies that treated high-risk neuroblastoma patients with 13-cisRA and immunotherapy.

Methods: Blood samples from COG high-risk neuroblastoma phase III clinical trials (A3973, ANBL0532, ANBL0032, and ANBL0931) were obtained for PK analyses. Plasma levels of 13-cisRA and 4-oxo-13-cisRA were measured using high-performance liquid chromatography for all patients treated with 13-cisRA. The relationship of PK to outcome was analyzed for the patient subgroup treated with 13-cisRA and ch14.18 anti-GD2 antibody + cytokines. PK variables analyzed included plasma levels of 13-cisRA, 4-oxo-13-cisRA, and the sum of both.

Results: Of 617 patients, 370 (60%) achieved median plasma concentrations of 13-cisRA + 4-oxo-13-cisRA (combined) &gt;5 μM. Plasma levels were higher in patients taking intact capsules relative to open-capsule takers (13-cisRA: 1.74 vs. 1.03, 4-oxo-13-cisRA: 7.2 vs. 3.3 μM, P &lt; 0.001). Both 13-cisRA and 4-oxo-13-cisRA concentrations positively correlated with older age (P &lt; 0.001). The relationship of PK to overall survival (OS) was analyzed for 524 patients treated with 13-cisRA and immunotherapy on ANBL0032 or ANBL0931. In patients ≥18 months old at diagnosis (n=445/524) the 5-year OS was significantly higher for patients with upper quartile 13-cisRA levels (2.5 μM, 73%) relative to lower quartile (0.6 μM, 60%, P = 0.039) although event-free survival was not significantly different (P = 0.44). Higher active metabolite concentrations (4-oxo-13-cisRA &gt;5 µM, 76%) was also associated with significantly higher OS relative to lower levels (&lt;1 µM, 66%, P = 0.032).

Conclusions: Age and route of administration influenced plasma levels of 13-cisRA and 4-oxo-13-cisRA. Combined levels of 13-cisRA and the active metabolite (4-oxo-13-cisRA) were &gt;5 µM in 85% of patients. In patients ≥18 months old, low plasma levels of 13-cisRA and 4-oxo-13-cisRA were associated with a lower overall survival.

Citation Format: Hwangeui Cho, Arlene Naranjo, Collin Van Ryn, Shengping Yang, Poonam Sonawane, Judith G. Villablanca, Alice L. You, Julie R. Park, Susan Kreissman, C Patrick Reynolds, Min H. Kang. Low plasma levels of 13-cis-retinoic acid (isotretinoin) and its active metabolite 4-oxo-13-cis-retinoic acid are associated with lower overall survival of high-risk neuroblastoma patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-049. doi:10.1158/1538-7445.AM2017-LB-049

Abstract 2038: Reactive oxygen species-mediated synergism of fenretinide and romidepsin in preclinical models of T-cell lymphoid malignancies

Introduction: T-cell lymphoid malignancies (TCLMs) are in need of novel and more effective therapies. Romidepsin is a histone deacetylase (HDAC) inhibitor that achieved FDA registration as 2nd line therapy for peripheral and cutaneous T-cell lymphomas. The cytotoxic retinoid fenretinide achieved durable complete responses against T-cell lymphomas in early-phase clinical trials and T-cell lymphoma patients who failed prior romidepsin treatment responded to fenretinide. Fenretinide is currently being evaluated in a Phase IIa clinical trial for relapsed/refractory PTCL patients (NCT02495415). We investigated the potential for using these two agents in combination in TCLMs. Methods and Results: Using the DIMSCAN assay, we demonstrated cytotoxic synergy between romidepsin and fenretinide in fifteen TCLM cell lines at clinically-achievable concentrations that lacked cytotoxicity for non-malignant cells (fibroblasts and blood mononuclear cells). In vivo, romidepsin + fenretinide + ketoconazole (enhances fenretinide exposures by inhibiting fenretinide metabolism) showed greater activity in subcutaneous (COG-LL-317m and TX-LY-183x PDX) and disseminated (COG-LL-317m Luc expressing the luciferase gene) TCLM xenograft models than single agent romidepsin or fenretinide + ketoconazole. Fenretinide + romidepsin caused a reactive oxygen species (ROS, measured by DCFDA dye)-dependent increase in pro-apoptotic proteins (Bim, tBid, Bax and Bad), apoptosis (via TUNEL assay), and inhibition of HDAC enzymatic activity, which achieved a synergistic increase in histone acetylation. The synergistic cytotoxicity, apoptosis, and histone acetylation of fenretinide + romidepsin was abrogated by antioxidants (vitamins C or E). Romidepsin + fenretinide activated p38 and JNK via ROS, and shRNA knockdown of p38 and JNK1 significantly decreased the synergistic cytotoxicity and apoptosis. Romidepsin + fenretinide also showed synergistic cytotoxicity for B-lymphoid malignancy cell lines, but did not increase ROS, acetylation of histones, activation of p38 + JNK, or cytotoxicity in fibroblasts and blood mononuclear cells. Conclusion: Romidepsin + fenretinide achieved synergistic activity in preclinical models of TCLMs, but not in non-malignant cells, via a novel molecular mechanism. These data support conducting clinical trials of romidepsin + fenretinide in relapsed and refractory TCLMs.

Citation Format: Monish Ram Makena, Balakrishna Koneru, Min H. Kang, C. Patrick Reynolds. Reactive oxygen species-mediated synergism of fenretinide and romidepsin in preclinical models of T-cell lymphoid malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2038. doi:10.1158/1538-7445.AM2017-2038

Clinical development of fenretinide as an antineoplastic drug: Pharmacology perspectives

Fenretinide (4-HPR) is a synthetic retinoid that has cytotoxic activity against cancer cells. Despite substantial in vitro cytotoxicity, response rates in early clinical trials with 4-HPR have been less than anticipated, likely due to the low bioavailability of the initial oral capsule formulation. Several clinical studies have shown that the oral capsule formulation at maximum tolerated dose (MTD) achieved <10 µmol/L concentrations in patients. To improve bioavailability of 4-HPR, new oral powder (LYM-X-SORB®, LXS) and intravenous lipid emulsion (ILE) formulations are being tested in early-phase clinical trials. ILE 4-HPR administered as five-day continuous infusion achieved over 50 µmol/L at MTD with minimal systemic toxicities; multiple complete and partial responses were observed in peripheral T cell lymphomas. The LXS oral powder 4-HPR formulation increased plasma levels approximately two-fold at MTD in children without dose-limiting toxicities and demonstrated multiple complete responses in recurrent neuroblastoma. The clinical activity observed with new 4-HPR formulations is attributed to increased bioavailability. Phase I and II clinical trials of both LXS 4-HPR and ILE 4-HPR are in progress as a single agent or in combination with other drugs. Impact statement One of the critical components in drug development is understanding pharmacology (especially pharmacokinetics) of the drugs being developed. Often the pharmacokinetic properties, such as poor solubility leading to poor bioavailability, of the drug can limit further development of the drug. The development of numerous drugs has often halted at clinical testing stages, and several of them were due to the pharmacological properties of the agents, resulting in increased drug development cost. The current review provides an example of how improved clinical activity can be achieved by changing the formulations of a drug with poor bioavailability. Thus, it emphasizes the importance of understanding pharmacologic characteristics of the drug in drug development.

P450 inhibitor ketoconazole increased the intratumor drug levels and antitumor activity of fenretinide in human neuroblastoma xenograft models

We previously reported that concurrent ketoconazole, an oral anti-fungal agent and P450 enzyme inhibitor, increased plasma levels of the cytotoxic retinoid, fenretinide (4-HPR) in mice. We have now determined the effects of concurrent ketoconazole on 4-HPR cytotoxic dose-response in four neuroblastoma (NB) cell lines in vitro and on 4-HPR activity against two cell line-derived, subcutaneous NB xenografts (CDX) and three patient-derived NB xenografts (PDX). Cytotoxicity in vitro was assessed by DIMSCAN assay. Xenografted animals were treated with 4-HPR/LXS (240 mg/kg/day) + ketoconazole (38 mg/kg/day) in divided oral doses in cycles of five continuous days a week. In one model, intratumoral levels of 4-HPR and metabolites were assessed by HPLC assay, and in two models intratumoral apoptosis was assessed by TUNEL assay, on Day 5 of the first cycle. Antitumor activity was assessed by Kaplan-Meier event-free survival (EFS). The in vitro cytotoxicity of 4-HPR was not affected by ketoconazole (p ≥ 0.06). Ketoconazole increased intratumoral levels of 4-HPR (p = 0.02), of the active 4-oxo-4-HPR metabolite (p = 0.04), and intratumoral apoptosis (p ≤ 0.0006), compared to 4-HPR/LXS-alone. Concurrent ketoconazole increased EFS in both CDX models compared to 4-HPR/LXS-alone (p ≤ 0.008). 4-HPR + ketoconazole also increased EFS in PDX models compared to controls (p ≤ 0.03). Thus, concurrent ketoconazole decreased 4-HPR metabolism with resultant increases of plasma and intratumoral drug levels and antitumor effects in neuroblastoma murine xenografts. These results support the clinical testing of concurrent ketoconazole and oral fenretinide in neuroblastoma.

Phase I Study of Fenretinide Delivered Intravenously in Patients with Relapsed or Refractory Hematologic Malignancies: A California Cancer Consortium Trial

Purpose: A phase I study was conducted to determine the MTD, dose-limiting toxicities (DLT), and pharmacokinetics of fenretinide delivered as an intravenous emulsion in relapsed/refractory hematologic malignancies.Experimental Design: Fenretinide (80-1,810 mg/m²/day) was administered by continuous infusion on days 1 to 5, in 21-day cycles, using an accelerated titration design.Results: Twenty-nine patients, treated with a median of three prior regimens (range, 1-7), were enrolled and received the test drug. Ninety-seven courses were completed. An MTD was reached at 1,280 mg/m²/day for 5 days. Course 1 DLTs included 6 patients with hypertriglyceridemia, 4 of whom were asymptomatic; 2 patients experienced DLT thrombocytopenia (asymptomatic). Of 11 patients with response-evaluable peripheral T-cell lymphomas, two had complete responses [CR, progression-free survival (PFS) 68+ months; unconfirmed CR, PFS 14+ months], two had unconfirmed partial responses (unconfirmed PR, PFS 5 months; unconfirmed PR, PFS 6 months), and five had stable disease (2-12 cycles). One patient with mature B-cell lymphoma had an unconfirmed PR sustained for two cycles. Steady-state plasma levels were approximately 10 mcg/mL (mid-20s μmol/L) at 640 mg/m²/day, approximately 14 mcg/mL (mid-30s μmol/L) at 905 mg/m²/day, and approximately 22 mcg/mL (mid-50s μmol/L) at 1,280 mg/m²/day.Conclusions: Intravenous fenretinide obtained significantly higher plasma levels than a previous capsule formulation, had acceptable toxicities, and evidenced antitumor activity in peripheral T-cell lymphomas. A recommended phase II dosing is 600 mg/m² on day 1, followed by 1,200 mg/m² on days 2 to 5, every 21 days. A registration-enabling phase II study in relapsed/refractory PTCL (ClinicalTrials.gov identifier: NCT02495415) is ongoing. Clin Cancer Res; 23(16); 4550-5. ©2017 AACR.

Initial testing (stage 1) of the curaxin CBL0137 by the pediatric preclinical testing program

BACKGROUND

CBL0137 is a novel drug that modulates FAcilitates Chromatin Transcription (FACT), resulting in simultaneous nuclear factor-κB suppression, heat shock factor 1 suppression and p53 activation. CBL0137 has demonstrated antitumor effects in animal models of several adult cancers and neuroblastoma.

PROCEDURES

CBL0137 was tested against the Pediatric Preclinical Testing Program (PPTP) in vitro cell line panel at concentrations ranging from 1.0 nM to 10.0 μM and against the PPTP in vivo solid tumor xenograft and acute lymphocytic leukemia (ALL) panels at 50 mg/kg administered intravenously weekly for 4 weeks.

RESULTS

The median relative IC₅₀ (rIC₅₀ ) value for the PPTP cell lines was 0.28 μM (range: 0.13-0.80 μM). There were no significant differences in rIC₅₀ values by histotype. CBL0137 induced significant differences in event-free survival (EFS) distribution compared to control in 10 of 31 (32%) evaluable solid tumor xenografts and in eight of eight (100%) evaluable ALL xenografts. Significance differences in EFS distribution were observed in four of six osteosarcoma lines, three of three rhabdoid tumor lines and two of six rhabdomyosarcoma lines. No objective responses were observed among the solid tumor xenografts. For the ALL panel, one xenograft achieved complete response and four achieved partial response.

CONCLUSIONS

The most consistent in vivo activity for CBL0137 was observed against ALL xenografts, with some solid tumor xenograft lines showing tumor growth delay. It will be important to relate the drug levels in mice at 50 mg/kg to those in humans at the recommended phase 2 dose.

Initial Testing (Stage 1) of MK-8242-A Novel MDM2 Inhibitor-by the Pediatric Preclinical Testing Program

BACKGROUND

MK-8242 is an inhibitor of MDM2 that stabilizes the tumor suppressor TP53 and induces growth arrest or apoptosis downstream of TP53 induction.

PROCEDURES

MK-8242 was tested against the Pediatric Preclinical Testing Program (PPTP) in vitro cell line panel at concentrations from 1.0 nM to 10.0 μM and against the PPTP in vivo xenograft panels using oral gavage on Days 1-5 and Day 15-19 at a dose of 125 mg/kg (solid tumors) or 75 mg/kg (acute lymphoblastic leukemia [ALL] models).

RESULTS

The median IC50 for MK-8242 was 0.07 μM for TP53 wild-type cell lines versus >10 μM for TP53 mutant cell lines. MK-8242 induced a twofold or greater delay in time to event in 10 of 17 (59%) of TP53 wild-type solid tumor xenografts, excluding osteosarcoma xenografts that have very low TP53 expression. Objective responses were observed in seven solid tumor xenografts representing multiple histotypes. For the systemic-disease ALL panel, among eight xenografts there were two complete responses (CRs) and six partial responses (PRs). Two additional MLL-rearranged xenografts (MV4;11 and RS4;11) grown subcutaneously showed maintained CR and PR, respectively. The expected pharmacodynamic responses to TP53 activation were observed in TP53 wild-type models treated with MK-8242. Pharmacokinetic analysis showed that MK-8242 drug exposure in SCID mice appears to exceed that was observed in adult phase 1 trials.

CONCLUSIONS

MK-8242-induced tumor regressions across multiple solid tumor histotypes and induced CRs or PRs for most ALL xenografts. This activity was observed at MK-8242 drug exposures that appear to exceed those observed in human phase 1 trials.

Evaluation of Alternative In Vivo Drug Screening Methodology: A Single Mouse Analysis

Traditional approaches to evaluating antitumor agents using human tumor xenograft models have generally used cohorts of 8 to 10 mice against a limited panel of tumor models. An alternative approach is to use fewer animals per tumor line, allowing a greater number of models that capture greater molecular/genetic heterogeneity of the cancer type. We retrospectively analyzed 67 agents evaluated by the Pediatric Preclinical Testing Program to determine whether a single mouse, chosen randomly from each group of a study, predicted the median response for groups of mice using 83 xenograft models. The individual tumor response from a randomly chosen mouse was compared with the group median response using established response criteria. A total of 2,134 comparisons were made. The single tumor response accurately predicted the group median response in 1,604 comparisons (75.16%). The mean tumor response correct prediction rate for 1,000 single mouse random samples was 78.09%. Models had a range for correct prediction (60%-87.5%). Allowing for misprediction of ± one response category, the overall mean correct single mouse prediction rate was 95.28%, and predicted overall objective response rates for group data in 66 of 67 drug studies. For molecularly targeted agents, occasional exceptional responder models were identified and the activity of that agent confirmed in additional models with the same genotype. Assuming that large treatment effects are targeted, this alternate experimental design has similar predictive value as traditional approaches, allowing for far greater numbers of models to be used that more fully encompass the heterogeneity of disease types. Cancer Res; 76(19); 5798-809. ©2016 AACR.

A Phase I New Approaches to Neuroblastoma Therapy Study of Buthionine Sulfoximine and Melphalan With Autologous Stem Cells for Recurrent/Refractory High-Risk Neuroblastoma

BACKGROUND

Myeloablative therapy for high-risk neuroblastoma commonly includes melphalan. Increased cellular glutathione (GSH) can mediate melphalan resistance. Buthionine sulfoximine (BSO), a GSH synthesis inhibitor, enhances melphalan activity against neuroblastoma cell lines, providing the rationale for a Phase 1 trial of BSO-melphalan.

PROCEDURES

Patients with recurrent/resistant high-risk neuroblastoma received BSO (3 gram/m(2) bolus, then 24 grams/m(2) /day infusion days -4 to -2), with escalating doses of intravenous melphalan (20-125 mg/m(2) ) days -3 and -2, and autologous stem cells day 0 using 3 + 3 dose escalation.

RESULTS

Among 28 patients evaluable for dose escalation, one dose-limiting toxicity occurred at 20 mg/m(2) melphalan (grade 3 aspartate aminotransferase/alanine aminotransferase) and one at 80 mg/m(2) (streptococcal bacteremia, grade 4 hypotension/pulmonary/hypocalcemia) without sequelae. Among 25 patients evaluable for response, there was one partial response (PR) and two mixed responses (MRs) among eight patients with prior melphalan exposure; one PR and three MRs among 16 patients without prior melphalan; one stable disease with unknown melphalan history. Melphalan pharmacokinetics with BSO were similar to reports for melphalan alone. Melphalan Cmax for most patients was below the 10 μM concentration that showed neuroblastoma preclinical activity with BSO.

CONCLUSIONS

BSO (75 gram/m(2) ) with melphalan (125 mg/m(2) ) is tolerable with stem cell support and active in recurrent/refractory neuroblastoma. Further dose escalation is feasible and may increase responses.

Conjugated polyelectrolyte nano field emission adlayers

Here we report on a straightforward and rapid means of enhancing the field electron emission performance of nascent vertically aligned multi-walled carbon nanotubes by introducing a polar zwitterionic conjugated polyelectrolyte adlayer at the vacuum-emitter interface. We attribute the observed 66% decrease in turn-on electric field to the augmented emitter micro-morphology and shifted surface band structure. The composite emitters can be optically modulated by exploiting the absorption cross-section of the solution cast adlayer, which increases the local carrier concentration which broadens the effective electrostatic shape of the emitter during optical excitation. Assessment via scanning anode field emission microscopy reveals a 25% improvement in DC time stability, a significant reduction in long-term hysteresis shift, and a threefold increase in bandwidth during pulsed mode operation.

Activity of MM-398, nanoliposomal irinotecan (nal-IRI), in Ewing's family tumor xenografts is associated with high exposure of tumor to drug and high SLFN11 expression

PURPOSE

To determine the pharmacokinetics and the antitumor activity in pediatric cancer models of MM-398, a nanoliposomal irinotecan (nal-IRI).

EXPERIMENTAL DESIGN

Mouse plasma and tissue pharmacokinetics of nal-IRI and the current clinical formulation of irinotecan were characterized. In vivo activity of irinotecan and nal-IRI was compared in xenograft models (3 each in nu/nu mice) of Ewing's sarcoma family of tumors (EFT), neuroblastoma (NB), and rhabdomyosarcoma (RMS). SLFN11 expression was assessed by Affymetrix HuEx arrays, Taqman RT-PCR, and immunoblotting.

RESULTS

Plasma and tumor concentrations of irinotecan and SN-38 (active metabolite) were approximately 10-fold higher for nal-IRI than for irinotecan. Two doses of NAL-IRI (10 mg/kg/dose) achieved complete responses maintained for >100 days in 24 of 27 EFT-xenografted mice. Event-free survival for mice with RMS and NB was significantly shorter than for EFT. High SLFN11 expression has been reported to correlate with sensitivity to DNA damaging agents; median SLFN11 mRNA expression was >100-fold greater in both EFT cell lines and primary tumors compared with NB or RMS cell lines or primary tumors. Cytotoxicity of SN-38 inversely correlated with SLFN11 mRNA expression in 20 EFT cell lines.

CONCLUSIONS

In pediatric solid tumor xenografts, nal-IRI demonstrated higher systemic and tumor exposures to SN-38 and improved antitumor activity compared with the current clinical formulation of irinotecan. Clinical studies of nal-IRI in pediatric solid tumors (especially EFT) and correlative studies to determine if SLFN11 expression can serve as a biomarker to predict nal-IRI clinical activity are warranted.

Initial Testing of NSC 750854, a Novel Purine Analog, Against Pediatric Tumor Models by the Pediatric Preclinical Testing Program

BACKGROUND

NSC 750854 is a purine analog with an antitumor activity profile distinctive from that of other anticancer purines. It has shown significant activity against adult cancer preclinical models.

PROCEDURE

NSC 750854 was tested against the Pediatric Preclinical Testing Program (PPTP) in vitro cell line panel at concentrations from 1.0 nM to 10 μM and against the PPTP in vivo xenograft panels administered intraperitoneally at a dose of 5 mg/kg daily for 5 days repeated at day 15.

RESULTS

The median relative IC50 (rIC50 ) value for the PPTP cell lines was 32 nM (range from 11 to 124 nM), with consistent cytotoxicity across all cell lines. Acute lymphoblastic leukemia (ALL) cell lines were more sensitive to NSC 750854 than non-ALL cell lines. NSC 750854 induced significant differences in EFS distribution compared to control in 31 of 35 (89%) solid tumor xenografts. It induced tumor growth inhibition meeting criteria for intermediate or high event free survival (EFS) T/C activity in 17 of 32 (53%) evaluable solid tumor xenografts (most consistently in the rhabdomyosarcoma panel). Objective responses were observed in 15 of 37 (41%) solid tumor xenografts and in all eight leukemia models with complete response (CR) or maintained complete response (MCR) in seven of eight leukemia models.

CONCLUSIONS

NSC 750854 has a unique spectrum of antitumor activity compared with other agents tested by the PPTP as it induces regression in tumor models with limited sensitivity to most agents tested to date. Given the promising level of activity observed for NSC 750854 against PPTP preclinical models, further exploration of its mechanism of action is warranted.

Pharmacodynamic and genomic markers associated with response to the XPO1/CRM1 inhibitor selinexor (KPT-330): A report from the pediatric preclinical testing program

BACKGROUND

Selinexor (KPT-330) is an inhibitor of the major nuclear export receptor, exportin 1 (XPO1, also termed chromosome region maintenance 1, CRM1) that has demonstrated activity in preclinical models and clinical activity against several solid and hematological cancers.

PROCEDURES

Selinexor was tested against the Pediatric Preclinical Testing Program (PPTP) in vitro cell line panel at concentrations from 1.0 nM to 10 μM and against the PPTP in vivo xenograft panels administered orally at a dose of 10 mg/kg thrice weekly for 4 weeks.

RESULTS

Selinexor demonstrated cytotoxic activity in vitro, with a median relative IC50 value of 123 nM (range 13.0 nM to >10 μM). Selinexor induced significant differences in event-free survival (EFS) distribution in 29 of 38 (76%) of the evaluable solid tumor xenografts and in five of eight (63%) of the evaluable ALL xenografts. Objective responses (partial or complete responses, PR/CR) were observed for 4 of 38 solid tumor xenografts including Wilms tumor, medulloblastoma (n = 2), and ependymoma models. For the ALL panel, two of eight (25%) xenografts achieved either CR or maintained CR. Two responding xenografts had FBXW7 mutations at R465 and two had SMARCA4 mutations. Selinexor induced p53, p21, and cleaved PARP in several solid tumor models.

CONCLUSIONS

Selinexor induced regression against several solid tumor and ALL xenografts and slowed tumor growth in a larger number of models. Pharmacodynamic effects for XPO1 inhibition were noted. Defining the relationship between selinexor systemic exposures in mice and humans will be important in assessing the clinical relevance of these results.

Initial testing (stage 1) of the anti-microtubule agents cabazitaxel and docetaxel, by the pediatric preclinical testing program

BACKGROUND

Although microtubule-destabilizing agents (principally vincristine) are in common use in pediatric oncology, the microtubule-stabilizing taxanes are uncommonly used to treat childhood cancers. Cabazitaxel has been reported to have activity superior to that of docetaxel in preclinical models of multidrug-resistant adult cancers, and it was active in patients who had progressed on or after docetaxel. The PPTP conducted a comparison of these two agents against the PPTP in vitro panel and against a limited panel of solid tumor xenografts.

PROCEDURES

Cabazitaxel and docetaxel were tested against the PPTP in vitro cell line panel at concentrations from 0.01 to 0.1 μM and in vivo against a subset of the PPTP solid tumor xenograft models at a dose of 10 or 7.5 mg/kg on an every 4 days × 3 I.V. schedule.

RESULTS

In vitro, both cabazitaxel and docetaxel had similar potency (median rIC50 0.47 nM and 0.88 nM, respectively) and a similar activity profile, with Ewing sarcoma cells being significantly more sensitive to both agents. In vitro sensitivity to docetaxel inversely correlated with mRNA expression for ABCB1, but the correlation with ABCB1 expression was weaker for cabazitaxel. In vivo cabazitaxel demonstrated significantly greater activity than docetaxel in five of 12 tumor models, inducing regressions in six models compared with three models for docetaxel.

CONCLUSIONS

Cabazitaxel demonstrated superior activity compared to docetaxel. The lower cabazitaxel systemic exposure tolerated in humans compared to mice needs to be considered when extrapolating these results to the clinical setting.

Metabolic characteristics of 13-cis-retinoic acid (isotretinoin) and anti-tumour activity of the 13-cis-retinoic acid metabolite 4-oxo-13-cis-retinoic acid in neuroblastoma

BACKGROUND AND PURPOSE

Isotretinoin (13-cis-retinoic acid; 13-cRA) is a differentiation inducer used to treat minimal residual disease after myeloablative therapy for high-risk neuroblastoma. However, more than 40% of children develop recurrent disease during or after 13-cRA treatment. The plasma concentrations of 13-cRA in earlier studies were considered subtherapeutic while 4-oxo-13-cis-RA (4-oxo-13-cRA), a metabolite of 13-cRA considered by some investigators as inactive, were greater than threefold higher than 13-cRA. We sought to define the metabolic pathways of 13-cRA and investigated the anti-tumour activity of its major metabolite, 4-oxo-13-cRA.

EXPERIMENTAL APPROACH

Effects of 13-cRA and 4-oxo-13-cRA on human neuroblastoma cell lines were assessed by DIMSCAN and flow cytometry for cell proliferation, MYCN down-regulation by reverse transcription PCR and immunoblotting, and neurite outgrowth by confocal microscopy. 13-cRA metabolism was determined using tandem MS in human liver microsomes and in patient samples.

KEY RESULTS

Six major metabolites of 13-cRA were identified in patient samples. Of these, 4-oxo-13-cRA was the most abundant, and 4-oxo-13-cRA glucuronide was also detected at a higher level in patients. CYP3A4 was shown to play a major role in catalysing 13-cRA to 4-oxo-13-cRA. In human neuroblastoma cell lines, 4-oxo-13-cRA and 13-cRA were equi-effective at inducing neurite outgrowth, inhibiting proliferation, decreasing MYCN mRNA and protein, and increasing the expression of retinoic acid receptor-β mRNA and protein levels.

CONCLUSIONS AND IMPLICATIONS

We showed that 4-oxo-13-cRA is as active as 13-cRA against neuroblastoma cell lines. Plasma levels of both 13-cRA and 4-oxo-13-cRA should be evaluated in pharmacokinetic studies of isotretinoin in neuroblastoma.

Delayed Presentation of Catheter-related Subclavian Artery Pseudoaneurysm

Central venous catheterization is a common diagnostic and therapeutic procedure in modern clinical practice. Pseudoaneurysms of the subclavian artery are rare and usually occur immediately after the causative event, whether the cause was trauma or a medical procedure. Here, we report a case of a 71-year-old woman with delayed presentation of catheter-related subclavian pseudoaneurysm. The patient’s symptoms began two weeks after the initial catheterization, probably because of slow leakage of blood from the injured subclavian artery caused by incomplete compression of the puncture site and uremic coagulopathy. She was successfully treated with ultrasound-guided thrombin and angiography-guided histoacryl injection without stent insertion or surgery. Keywords: butyl 2-cyanacrylate; pseudoaneurysm; subclavian; thrombin.