Identification of acquired Notch3 dependency in metastatic Head and Neck Cancer

During cancer development, tumor cells acquire changes that enable them to invade surrounding tissues and seed metastasis at distant sites. These changes contribute to the aggressiveness of metastatic cancer and interfere with success of therapy. Our comprehensive analysis of "matched" pairs of HNSCC lines derived from primary tumors and corresponding metastatic sites identified several components of Notch3 signaling that are differentially expressed and/or altered in metastatic lines and confer a dependency on this pathway. These components were also shown to be differentially expressed between early and late stages of tumors in a TMA constructed from over 200 HNSCC patients. Finally, we show that suppression of Notch3 improves survival in mice in both subcutaneous and orthotopic models of metastatic HNSCC. Novel treatments targeting components of this pathway may prove effective in targeting metastatic HNSCC cells alone or in combination with conventional therapies.

Repurposing Itraconazole and Hydroxychloroquine to Target Lysosomal Homeostasis in Epithelial Ovarian Cancer

Drug repurposing is an attractive option for oncology drug development. Itraconazole is an antifungal ergosterol synthesis inhibitor that has pleiotropic actions including cholesterol antagonism, inhibition of Hedgehog and mTOR pathways. We tested a panel of 28 epithelial ovarian cancer (EOC) cell lines with itraconazole to define its spectrum of activity. To identify synthetic lethality in combination with itraconazole, a whole-genome drop-out genome-scale clustered regularly interspaced short palindromic repeats sensitivity screen in two cell lines (TOV1946 and OVCAR5) was performed. On this basis, we conducted a phase I dose-escalation study assessing the combination of itraconazole and hydroxychloroquine in patients with platinum refractory EOC (NCT03081702). We identified a wide spectrum of sensitivity to itraconazole across the EOC cell lines. Pathway analysis showed significant involvement of lysosomal compartments, the trans-golgi network and late endosomes/lysosomes; similar pathways are phenocopied by the autophagy inhibitor, chloroquine. We then demonstrated that the combination of itraconazole and chloroquine displayed Bliss defined synergy in EOC cancer cell lines. Furthermore, there was an association of cytotoxic synergy with the ability to induce functional lysosome dysfunction, by chloroquine. Within the clinical trial, 11 patients received at least one cycle of itraconazole and hydroxychloroquine. Treatment was safe and feasible with the recommended phase II dose of 300 and 600 mg twice daily, respectively. No objective responses were detected. Pharmacodynamic measurements on serial biopsies demonstrated limited pharmacodynamic impact. In vitro, itraconazole and chloroquine have synergistic activity and exert a potent antitumor effect by affecting lysosomal function. The drug combination had no clinical antitumor activity in dose escalation.

Significance

The combination of the antifungal drug itraconazole with antimalarial drug hydroxychloroquine leads to a cytotoxic lysosomal dysfunction, supporting the rational for further research on lysosomal targeting in ovarian cancer.

Multimerin-2 orchestrates the cross-talk between endothelial cells and pericytes: A mechanism to maintain vascular stability

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The ECM Multimerin-2 is a substrate for pericyte adhesion.

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The recruitment of pericytes leads to enhanced Multimerin-2 expression by endothelial cells.

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Multimerin-2 induces the expression of important cytokines both in endothelial cells and pericytes.

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The deposition of Multimerin-2 is key for the endothelial cell/pericyte crosstalk required for the establishment of vascular stability.

Tumor angiogenesis is vital for the growth and development of various solid cancers and as such is a valid and promising therapeutic target. Unfortunately, the use of the currently available anti-angiogenic drugs increases the progression-free survival by only a few months. Conversely, targeting angiogenesis to prompt both vessel reduction and normalization, has been recently viewed as a promising approach to improve therapeutic efficacy. As a double-edged sword, this line of attack may on one side halt tumor growth as a consequence of the reduction of nutrients and oxygen supplied to the tumor cells, and on the other side improve drug delivery and, hence, efficacy. Thus, it is of upmost importance to better characterize the mechanisms regulating vascular stability. In this context, recruitment of pericytes along the blood vessels is crucial to their maturation and stabilization. As the extracellular matrix molecule Multimerin-2 is secreted by endothelial cells and deposited also in juxtaposition between endothelial cells and pericytes, we explored Multimerin-2 role in the cross-talk between the two cell types. We discovered that Multimerin-2 is an adhesion substrate for pericytes. Interestingly, and consistent with the notion that Multimerin-2 is a homeostatic molecule deposited in the later stages of vessel formation, we found that the interaction between endothelial cells and pericytes promoted the expression of Multimerin-2. Furthermore, we found that Multimerin-2 modulated the expression of key cytokines both in endothelial cells and pericytes. Collectively, our findings posit Multimerin-2 as a key molecule in the cross-talk between endothelial cells and pericytes and suggest that the expression of this glycoprotein is required to maintain vascular stability.

A phase I/II study of hydroxychloroquine and suba-itraconazole in men with biochemical relapse of prostate cancer (HITMAN-PC): Dose escalation results

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Background: Preclinical data show hydroxychloroquine (HCQ) and suba-itraconazole (SI) together enhance prostate cancer cell death. The proposed mechanism is lysosome dysfunction including sequestration of cholesterol in endosomes and inhibition of gogi-lyosome trafficking. HCQ/SI could delay androgen deprivation therapy (ADT) and its associated morbidity in men with biochemical relapse of prostate cancer. In this phase I/II study, maximum tolerated dose (MTD), recommended phase II dose (RP2D), safety, pharmacokinetics (PK), and preliminary activity of HCQ/SI was investigated in such patients. Methods: Patients received escalating doses of HCQ with fixed SI 150mg BD in rolling 6 design. This will be followed by a planned phase II Simon 2-stage cohort expansion. Results: Eleven men were treated with HCQ/SI. Median age 73 (range 69-77), baseline PSA 4.4 µg/L (1.6-22.4) and doubling time 5.3 months (3.3-15.3). Two experienced dose-limiting toxicity: grade 3 diarrhoea and grade 3 alanine transferase elevation, both at HCQ 600mg BD. Most common treatment-related adverse events (AEs) were hypertension (91% all grade/18% grade 3), QTc prolongation (55%/0%), diarrhoea (36%/9%), and nausea (36%/0%). There were no grade 4 AEs or deaths. While there were no PSA responses (≥50% fall from baseline), PSA PFS by PCWG3 criteria was 5.5 months (2.0-9.0), and PSA doubling time was prolonged at 4 and 12 weeks in 82% and 45% respectively. ADT-free and metastasis-free survival are 14.3 months (95% CI 4.9-23.8) and 15.9 months (95% CI unevaluable) respectively. PK data will be presented. Conclusions: HCQ/SI demonstrated acceptable safety with MTD 600mg BD and RP2D 400mg BD. There is early signal of activity and phase II enrolment is to begin. Clinical trial information: NCT03513211.

Emergence of Enzalutamide Resistance in Prostate Cancer is Associated with BCL-2 and IKKB Dependencies

PURPOSE

Although enzalutamide (ENZ) has been widely used to treat de novo or castration-resistant metastatic prostate cancer, resistance develops and disease progression is ultimately inevitable. There are currently no approved targeted drugs to specifically delay or overcome ENZ resistance.

EXPERIMENTAL DESIGN

We selected several ENZ-resistant cell lines that replicated clinical characteristics of the majority of patients with ENZ-resistant disease. A high-throughput pharmacologic screen was utilized to identify compounds with greater cytotoxic effect for ENZ-resistant cell lines, compared with parental ENZ-sensitive cells. We validated the potential hits in vitro and in vivo, and used knockdown and overexpression assays to study the dependencies in ENZ-resistant prostate cancer.

RESULTS

ABT199 (BCL-2 inhibitor) and IMD0354 (IKKB inhibitor) were identified as potent and selective inhibitors of cell viability in ENZ-resistant cell lines in vitro and in vivo which were further validated using loss-of-function assays of BCL-2 and IKKB. Notably, we observed that overexpression of BCL-2 and IKKB in ENZ-sensitive cell lines was sufficient for the emergence of ENZ resistance. In addition, we confirmed that BCL-2 or IKKB inhibitors suppressed the development of ENZ resistance in xenografts. However, validation of both BCL-2 and IKKB in matched castration-sensitive/resistant clinical samples showed that, concurrent with the development of ENZ/abiraterone resistance in patients, only the protein levels of IKKB were increased.

CONCLUSIONS

Our findings identify BCL-2 and IKKB dependencies in clinically relevant ENZ-resistant prostate cancer cells in vitro and in vivo, but indicate that IKKB upregulation appears to have greater relevance to the progression of human castrate-resistant prostate cancer.

Abstract 3401: Targeting lysosomal homeostasis in ovarian cancer through drug repurposing

Background: Drug repurposing has become increasingly attractive as it avoids the long processes and costs associated with drug discovery. Itraconazole (Itra) is a broad-spectrum anti-fungal agent which has an established broad spectrum of activity in human cell lines including cholesterol antagonism and inhibition of Hedgehog and mTOR pathways. Many in vitro, in vivo and clinical studies have suggested anti-proliferative activity both alone and in combination with other chemotherapeutic agents, in particular in ovarian cancer. This study is aimed at supporting the therapeutic potential of Itra and discovering and repurposing new drugs that can increase Itra anticancer activity as well as identifying new targets in the treatment of ovarian cancer.

Methods: We tested a panel of 32 ovarian cancer cell lines with different doses of Itra and identified a subset of cells which showed significant sensitivity to the drug. To identify genetic vulnerabilities and find new therapeutic targets to combine with Itra, we performed a whole genome sensitivity CRISPR screen in 2 cell lines (TOV1946 and OVCAR5) treated with non-toxic (IC10) concentrations of Itra.

Results: Pathway analysis on the top hits from both the screens showed a significant involvement of lysosomal compartments, and in particular dynamics between trans Golgi network and late endosomes/lysosomes, pathways that are affected by the autophagy inhibitor Chloroquine (CQ). We subsequently demonstrated that the combination of Itra and CQ had a synergistic effect in many ovarian cancer cell lines, even in those resistant to Itra. Further, genetic and pharmacological manipulation of autophagy indicated that upstream inhibition of autophagy is not a key mediator of the Itra/CQ mechanism of action. However, combination of Itra with other lysosomotropic agents (Concanamycin A, Bafilomycin A and Tamoxifen) displayed overlapping activity with Itra/CQ, supporting the lysosomal involvement in sensitizing cells to Itra resulted from the CRISPR screens. Analysis of lysosomal pattern and function showed a combined effect of Itra and CQ in targeting lysosomes and neutralizing their activity.

Conclusion: We identified two FDA approved drugs – CQ and Tamoxifen - that can be used in combination with Itra and exert a potent anti-tumor effect in ovarian cancer by affecting lyosomal function and suggesting a likely dependency of these cells on lysosomal biology. Further studies are in progress.

Citation Format: Stefano Marastoni, Aleksandra Pesic, Sree Narayanan Nair, Zhu Juan Li, Ali Madani, Benjamin Haibe-Kains, Bradly G. Wouters, Anthony Joshua. Targeting lysosomal homeostasis in ovarian cancer through drug repurposing [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 3401.

Phase I/II trial assessing hydroxychloroquine and itraconazole in women with advanced platinum-resistant epithelial ovarian cancer (EOC) (HYDRA-01)

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Background: Autophagy is a mechanism of resistance to platinum chemotherapy. Itraconazole (Itr), an antifungal agent, can alter cholesterol-trafficking, leading to accumulation of cholesterol in endosomes/lysosomes and resulting in cancer cell death. Itr is also involved in regulation of angiogenesis, mTOR and Hedgehog pathways. In preclinical studies the Itr effect can be enhanced by combining it with the autophagy inhibitor hydroxychloroquine (H). Drug repurposing studies with Itr have shown a signal of activity in prostate, lung and basal cell carcinoma. Methods: A rolling-6 phase I design was used to enroll patients (pts) with platinum-resistant/refractory EOC. Pts received Itr 300mg twice daily (BID) with H as per dose escalation schedule (range 200mg BID- 600mg BID), continuously in a 28-day cycle. Primary objective was establishment of MTD; secondary objective was objective response rate, progression free survival (PFS). Pre- and on-treatment biopsies were mandatory to evaluate exploratory objectives assessing effect on apoptosis/proliferation, angiogenesis, cholesterol metabolism and mechanism of cytotoxicity. RNAseq and IHC was performed in the sequential biopsies. Results: 11 pts were enrolled, 9 evaluable for efficacy. Histology was high 91% and low-grade serous 9%. Median lines of prior therapy was 7. RP2D was Itr 300mg BID and H 600mg BID. 1 DLT was seen in dose-level 2 was grade 3 hypertension. Other grade ≥3 related toxicity were grade 3 hypokalemia and grade 4 QTc prolongation (1 pt, dose-level 3). No objective responses were observed and 1 pt had stable disease. Median PFS was 1.6 months (1-1.7). Pre- and on-treatment biopsy was available for 10 pts. Increase in autophagy related protein, LC3, P62 and lysosomal marker, LAMP1, expression by IHC was identified in 3 pts. RNAseq revealed no differences between pre and on treatment samples in cholesterol homeostasis, angiogenesis, lysosomal-autophagy, PI3K-mTOR pathways. Conclusions: The combination of Itr and H was feasible but did not show antitumour activity in this heavily pre-treated platinum resistant EOC population. Increase of IHC expression in autophagy related proteins was detected in 30% of pts but did not correlate with patient benefit. Clinical trial information: NCT03081702. [Table: see text]

Functional CRISPR and shRNA Screens Identify Involvement of Mitochondrial Electron Transport in the Activation of Evofosfamide

Evofosfamide (TH-302) is a hypoxia-activated DNA-crosslinking prodrug currently in clinical development for cancer therapy. Oxygen-sensitive activation of evofosfamide depends on one-electron reduction, yet the reductases that catalyze this process in tumors are unknown. We used RNA sequencing, whole-genome CRISPR knockout, and reductase-focused short hairpin RNA screens to interrogate modifiers of evofosfamide activation in cancer cell lines. Involvement of mitochondrial electron transport in the activation of evofosfamide and the related nitroaromatic compounds EF5 and FSL-61 was investigated using 143B ρ ⁰ (ρ zero) cells devoid of mitochondrial DNA and biochemical assays in UT-SCC-74B cells. The potency of evofosfamide in 30 genetically diverse cancer cell lines correlated with the expression of genes involved in mitochondrial electron transfer. A whole-genome CRISPR screen in KBM-7 cells identified the DNA damage-response factors SLX4IP, C10orf90 (FATS), and SLFN11, in addition to the key regulator of mitochondrial function, YME1L1, and several complex I constituents as modifiers of evofosfamide sensitivity. A reductase-focused shRNA screen in UT-SCC-74B cells similarly identified mitochondrial respiratory chain factors. Surprisingly, 143B ρ ⁰ cells showed enhanced evofosfamide activation and sensitivity but had global transcriptional changes, including increased expression of nonmitochondrial flavoreductases. In UT-SCC-74B cells, evofosfamide oxidized cytochromes a, b, and c and inhibited respiration at complexes I, II, and IV without quenching reactive oxygen species production. Our results suggest that the mitochondrial electron transport chain contributes to evofosfamide activation and that predicting evofosfamide sensitivity in patients by measuring the expression of canonical bioreductive enzymes such as cytochrome P450 oxidoreductase is likely to be futile.

The ablation of the matricellular protein EMILIN2 causes defective vascularization due to impaired EGFR-dependent IL-8 production affecting tumor growth

EMILIN2 is an extracellular matrix constituent playing an important role in angiogenesis; however, the underlying mechanism is unknown. Here we show that EMILIN2 promotes angiogenesis by directly binding epidermal growth factor receptor (EGFR), which enhances interleukin-8 (IL-8) production. In turn, IL-8 stimulates the proliferation and migration of vascular endothelial cells. Emilin2 null mice were generated and exhibited delayed retinal vascular development, which was rescued by the administration of the IL-8 murine ortholog MIP-2. Next, we assessed tumor growth and tumor-associated angiogenesis in these mice. Tumor cell growth in Emilin2 null mice was impaired as well as the expression of MIP-2. The vascular density of the tumors developed in Emilin2 null mice was prejudiced and vessels perfusion, as well as response to chemotherapy, decreased. Accordingly, human tumors expressing high levels of EMILIN2 were more responsive to chemotherapy. These results point at EMILIN2 as a key microenvironmental cue affecting vessel formation and unveil the possibility to develop new prognostic tools to predict chemotherapy efficacy.

EMILIN2 down-modulates the Wnt signalling pathway and suppresses breast cancer cell growth and migration

EMILIN2 is an extracellular matrix (ECM) protein that exerts contradictory effects within the tumour microenvironment: it induces apoptosis in a number of tumour cells, but it also enhances tumour neo-angiogenesis. In this study, we describe a new mechanism by which EMILIN2 attenuates tumour cell viability. Based on sequence homology with the cysteine-rich domain (CRD) of the Frizzled receptors, we hypothesized that EMILIN2 could affect Wnt signalling activation and demonstrate direct interaction with the Wnt1 ligand. This physical binding leads to decreased LRP6 phosphorylation and to the down-modulation of β-catenin, TAZ and their target genes. As a consequence, EMILIN2 negatively affects the viability, migration and tumourigenic potential of MDA-MB-231 breast cancer cells in a number of two- and three-dimensional in vitro assays. EMILIN2 does not modulate Wnt signalling downstream of the Wnt-Frizzled interaction, since it does not affect the activation of the pathway following treatment with the GSK3 inhibitors LiCl and CHIR99021. The interaction with Wnt1 and the subsequent biological effects require the presence of the EMI domain, as there is no effect with a deletion mutant lacking this domain. Moreover, in vivo experiments show that the ectopic expression of EMILIN2, as well as treatment with the recombinant protein, significantly reduce tumour growth and dissemination of cancer cells in nude mice. Accordingly, the tumour samples are characterized by a significant down-regulation of the Wnt signalling pathway. Altogether, these findings provide further evidence of the complex regulations governed by EMILIN2 in the tumour microenvironment, and they identify a key extracellular regulator of the Wnt signalling pathway.

mTOR pathway and mTOR inhibitors as agents for cancer therapy

Research into mTOR, mammalian Target Of Rapamycin as an important drug target continues to be extremely interesting, both in terms of the increased molecular knowledge being acquired at the basis of various human diseases, and also for possible applications in drug cancer therapy. The mTOR signaling system plays a key role in several transduction pathways that are necessary for cell cycle progression and cellular proliferation. Drugs known as mTOR inhibitors have been included in ongoing and in recently completed cancer trials. New insights into the mTOR signaling system are helping to clarify the functionality of key mTOR components, and especially their possible role in apoptosis, angiogenesis and tumor progression. Three other molecules, already approved for therapeutic use and being commercialized (Everolimius, Temsirolimus and Zotarolimus) are added to Rapamycin (also known as Sirolimus), the parent drug of the mTOR inhibitors. Of these, only Temsirolimus is currently approved in the treatment of renal cell carcinoma, while the others are approved for organ transplant rejection and coronary artery restenosis. There are at least 10 other molecules currently under development for clinical and preclinical studies. This review offers an updated synopsis of the mTOR signaling system, in particular as regards relevant aspects of cancer research, looks at the known mTOR inhibitors and gives a systematic vision of current trials for each individual molecule subject to clinical investigation.

Extracellular matrix: a matter of life and death

Extracellular matrix (ECM) is an essential component of the stromal microenvironment both from a structural and a functional point of view. The ECM functions as a scaffold for tissue organization and regulates growth factors and chemokines availability thus contributing to maintain tissue homeostasis. Attachment of cells to ECM is essential to support cell survival, growth, and proliferation, and the lack of these interactions can trigger a type of cell death named anoikis. Several studies point out that alterations of ECM composition are often responsible of many pathological conditions such as cancer, of which it has been demonstrated to be occasionally the main promoter. ECM does not always represent a prosurvival stimulus; among the different array of ECM molecules a set of proteins can negatively affect cell viability and are thought to play an important role in tumor progression. For this reason attention has been focused on these molecules as potential tools or targets for therapy.

EMILINs interact with anthrax protective antigen and inhibit toxin action in vitro

The informational spectrum method (ISM) is a virtual spectroscopy method for the fast analysis of potential protein-protein relationships. By applying the ISM approach to the GeneBank protein database the vascular proteins EMILIN1 (Elastin Microfibril Interface Located ProteIN), EMILIN2, MMN1, and MMN2 were identified as additional anthrax PA antigen interacting molecules. This virtual molecular interaction was formally proven by solid phase assays using recombinant proteins. The interaction is independent of the presence of divalent cations and does not involve PA aspartic residue at 683, a critical residue in receptor binding. In fact, the D683A point mutation fully prevented the cell intoxication ability of PA in the presence of Lethal Factor, but it was fully ineffective on the binding of mutated PA to EMILIN1 and EMILIN2. The ISM approach also led to the identification of the potential interaction sites between PA and EMILINs. A PA mutant with a deletion at residue D425 and solid phase protein-protein interaction studies as well as deletion mutant of EMILIN2 confirmed the hypothesized interaction site. Our findings imply that the PA-cell surface receptor interaction is not likely to provide the full explanation for the vascular lesions and prominent hemorrhages that follow Bacillus anthracis infection and spreading and call into play vascular associated proteins such as EMILINs as potential inhibitory proteins.

Regulation of the extrinsic apoptotic pathway by the extracellular matrix glycoprotein EMILIN2

Elastin microfibril interface-located proteins (EMILINs) constitute a family of extracellular matrix (ECM) glycoproteins characterized by the presence of an EMI domain at the N terminus and a gC1q domain at the C terminus. EMILIN1, the archetype molecule of the family, is involved in elastogenesis and hypertension etiology, whereas the function of EMILIN2 has not been resolved. Here, we provide evidence that the expression of EMILIN2 triggers the apoptosis of different cell lines. Cell death depends on the activation of the extrinsic apoptotic pathway following EMILIN2 binding to the TRAIL receptors DR4 and, to a lesser extent, DR5. Binding is followed by receptor clustering, colocalization with lipid rafts, death-inducing signaling complex assembly, and caspase activation. The direct activation of death receptors by an ECM molecule that mimics the activity of the known death receptor ligands is novel. The knockdown of EMILIN2 increases transformed cell survival, and overexpression impairs clonogenicity in soft agar and three-dimensional growth in natural matrices due to massive apoptosis. These data demonstrate an unexpected direct and functional interaction of an ECM constituent with death receptors and discloses an additional mechanism by which ECM cues can negatively affect cell survival.