Modulation of SLFN11 induces changes in DNA Damage response in breast cancer

BACKGROUND

Lack of Schlafen family member 11 (SLFN11) expression has been recently identified as a dominant genomic determinant of response to DNA damaging agents in numerous cancer types. Thus, several strategies aimed at increasing SLFN11 are explored to restore chemosensitivity of refractory cancers. In this study, we examined various approaches to elevate SLFN11 expression in breast cancer cellular models and confirmed a corresponding increase in chemosensitivity with using the most successful efficient one. As oncogenic transcriptomic downregulation is often driven by methylation of the promotor region, we explore the demethylation effect of 5-aza-2'-deoxycytidine (decitabine), on the SLFN11 gene. Since SLFN11 has been reported as an interferon inducible gene, and interferon is secreted during an active anti-tumor immune response, we investigated the in vitro effect of IFN-γ on SLFN11 expression in breast cancer cell lines. As a secondary approach to pick up cross talk between immune cells and SLFN11 expression we used indirect co-culture of breast cancer cells with activated PBMCs and evaluated if this can drive SLFN11 upregulation. Finally, as a definitive and specific way to modulate SLFN11 expression we implemented SLFN11 dCas9 (dead CRISPR associated protein 9) systems to specifically increase or decrease SLFN11 expression.

RESULTS

After confirming the previously reported correlation between methylation of SLFN11 promoter and its expression across multiple cell lines, we showed in-vitro that decitabine and IFN-γ could increase moderately the expression of SLFN11 in both BT-549 and T47D cell lines. The use of a CRISPR-dCas9 UNISAM and KRAB system could increase or decrease SLFN11 expression significantly (up to fivefold), stably and specifically in BT-549 and T47D cancer cell lines. We then used the modified cell lines to quantify the alteration in chemo sensitivity of those cells to treatment with DNA Damaging Agents (DDAs) such as Cisplatin and Epirubicin or DNA Damage Response (DDRs) drugs like Olaparib. RNAseq was used to elucidate the mechanisms of action affected by the alteration in SLFN11 expression. In cell lines with robust SLFN11 promoter methylation such as MDA-MB-231, no SLFN11 expression could be induced by any approach.

CONCLUSION

To our knowledge this is the first report of the stable non-lethal increase of SLFN11 expression in a cancer cell line. Our results show that induction of SLFN11 expression can enhance DDA and DDR sensitivity in breast cancer cells and dCas9 systems may represent a novel approach to increase SLFN11 and achieve higher sensitivity to chemotherapeutic agents, improving outcome or decreasing required drug concentrations. SLFN11-targeting therapies might be explored pre-clinically to develop personalized approaches.

An integrated tumor, immune and microbiome atlas of colon cancer

The lack of multi-omics cancer datasets with extensive follow-up information hinders the identification of accurate biomarkers of clinical outcome. In this cohort study, we performed comprehensive genomic analyses on fresh-frozen samples from 348 patients affected by primary colon cancer, encompassing RNA, whole-exome, deep T cell receptor and 16S bacterial rRNA gene sequencing on tumor and matched healthy colon tissue, complemented with tumor whole-genome sequencing for further microbiome characterization. A type 1 helper T cell, cytotoxic, gene expression signature, called Immunologic Constant of Rejection, captured the presence of clonally expanded, tumor-enriched T cell clones and outperformed conventional prognostic molecular biomarkers, such as the consensus molecular subtype and the microsatellite instability classifications. Quantification of genetic immunoediting, defined as a lower number of neoantigens than expected, further refined its prognostic value. We identified a microbiome signature, driven by Ruminococcus bromii, associated with a favorable outcome. By combining microbiome signature and Immunologic Constant of Rejection, we developed and validated a composite score (mICRoScore), which identifies a group of patients with excellent survival probability. The publicly available multi-omics dataset provides a resource for better understanding colon cancer biology that could facilitate the discovery of personalized therapeutic approaches.

Abstract B09: Exploring IKKβ as an antiangiogenic therapeutic target in KRAS-induced lung cancer

Activating mutations in KRAS are prevalent in cancer, but therapies targeted to oncogenic RAS have so far failed. An alternative route for blocking RAS-driven oncogenic pathways is to target downstream effectors of RAS involved in promoting the oncogenic phenotype. One of the critical characteristics required for tumors to grow and progress is the ability of tumor cells to drive angiogenesis. Interestingly, oncogenic RAS promotes angiogenesis by upregulating the proangiogenic IL-8 cytokine, an NF-κB target gene, and we have shown that NF-κB activation by KRAS requires the IKKβ kinase. Interestingly, IKKβ targeting only minimally affects KRAS-mutant cell growth in vitro, nonetheless it significantly reduces KRAS-induced lung tumor growth in situ. Therefore, we hypothesized that IKKβ inhibition would reduce KRAS-induced lung tumor growth by impairing angiogenesis. To test this hypothesis, we targeted IKKβ in KRAS-mutant lung cancer cell lines A549 and H358, both by RNAi and by treatment with Compound A (CmpdA), a highly specific IKKβ inhibitor. Both approaches reduced expression and secretion of IL-8 and VEGF, another NF-κB-regulated proangiogenic growth factor. Moreover, conditioned media from IKKβ-targeted lung cells reduced endothelial cell migration and tube formation in vitro. Furthermore, siRNA-mediated IKKβ inhibition reduced xenograft tumor growth and angiogenesis in vivo. Finally, we determined that IKKβ inhibition can affect endothelial cell function independently of cancer cells as well, as CmpdA treatment directly reduced endothelial cell migration and reduced pathologic retinal angiogenesis in a mouse model of neonatal retinopathy. Taken together, these results suggest that IKKβ inhibition therapy may be an important general antiangiogenic therapy and may reduce KRAS-induced lung tumor angiogenesis, thereby providing a clinical therapeutic benefit for lung cancer patients harboring KRAS mutations.

Citation Format: Tatiana C. Carneiro-Lobo, Edmilson Ozorio dos Santos, Luiza Coimbra Scalabrini, Laura B. Cardeal, Albert S. Baldwin, Ricardo José Giordano, Daniela S. Basseres. Exploring IKKβ as an antiangiogenic therapeutic target in KRAS-induced lung cancer [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr B09.

Hypoxia regulates the expression of tissue factor pathway signaling elements in a rat glioma model

Hypoxia and necrosis are fundamental features of glioma, and their emergence is critical for the rapid biological progression of this fatal tumor. The presence of vaso-occlusive thrombus is higher in grade IV tumors [glioblastoma multiforme (GBM)] compared with lower grade tumors, suggesting that the procoagulant properties of the tumor contribute to its aggressive behavior, as well as the establishment of tumor hypoxia and necrosis. Tissue factor (TF), the primary cellular initiator of coagulation, is overexpressed in GBMs and likely favors a thrombotic microenvironment. Phosphatase and tensin homolog (PTEN) loss and hypoxia are two common alterations observed in glioma that may be responsible for TF upregulation. In the present study, ST1 and P7 rat glioma lines, with different levels of aggressiveness, were comparatively analyzed with the aim of identifying differences in procoagulant mechanisms. The results indicated that P7 cells display potent procoagulant activity compared with ST1 cells. Flow cytometric analysis showed less pronounced levels of TF in ST1 cells compared with P7 cells. Notably, P7 cells supported factor X (FX) activation via factor VIIa, whereas no significant FXa generation was observed in ST1 cells. Furthermore, the exposure of phosphatidylserine on the surface of P7 and ST1 cells was investigated. The results supported the assembly of prothrombinase complexes, accounting for the production of thrombin. Furthermore, reverse transcription-quantitative polymerase chain reaction showed that CoCl₂ (known to induce a hypoxic-like stress) led to an upregulation of TF levels in P7 and ST1 cells. Therefore, increased TF expression in P7 cells was accompanied by increased TF procoagulant activity. In addition, hypoxia increased the shedding of procoagulant TF-bearing microvesicles in both cell lines. Finally, hypoxic stress induced by treatment with CoCl₂ upregulated the expression of the PAR1 receptor in both P7 and ST1 cells. In addition to PAR1, P7, but not ST1 cells, expressed higher levels of PAR2 under hypoxic stress. Thus, modulating these molecular interactions may provide additional insights for the development of more efficient therapeutic strategies against aggressive glioma.

Expression of tissue factor signaling pathway elements correlates with the production of vascular endothelial growth factor and interleukin-8 in human astrocytoma patients

The expression levels of tissue factor (TF), the clotting initiator protein, have been correlated with angiogenesis and the histological grade of malignancy in glioma patients. The pro-tumor function of TF is linked to a family of G protein-coupled receptors known as protease-activated receptors (PARs), which may be activated by blood coagulation proteases. Activation of PARs elicits a number of responses, including the expression of vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8). In the present study, we analyzed the expression of TF signaling pathway elements (TF, PAR1 and PAR2) and evaluated their correlation with the expression of downstream products (VEGF and IL-8) in human astrocytoma patients. Quantitative PCR (qPCR) showed a significant increase in TF expression in grade IV (glioblastoma) tumors, which was inversely correlated with the expression of the tumor-suppressor PTEN. Immunohistochemistry and qPCR analyses demonstrated a highly significant elevation in the expression of PAR1, but not PAR2, in tumor samples from high-grade astrocytoma patients. The elevated VEGF expression levels detected in the high-grade astrocytoma samples were positively correlated with TF, PAR1 and PAR2 expression. In addition, IL-8 was significantly increased in glioblastoma patients and positively correlated with TF and PAR2 expression. Further in vitro assays employing the human glioma cell lines U87-MG and HOG demonstrated that a synthetic peptide PAR2 agonist stimulated VEGF and IL-8 production. Our findings suggest a role for TF signaling pathway elements in astrocytoma progression, particularly in glioblastoma. Therefore, TF/PAR signaling elements may be suitable targets for the development of new therapies for the treatment of aggressive glioma.

The tick-derived inhibitor Ixolaris prevents tissue factor signaling on tumor cells

BACKGROUND

Tissue factor (TF) is frequently overexpressed in cancer cells and correlated with more aggressive tumor phenotypes and poor prognosis. In addition to promoting coagulation-dependent metastasis and cancer-associated thrombosis, tumor cell-expressed TF mediates direct cell signaling involving the protease-activated receptor (PAR) 2. Ixolaris is a tick-derived inhibitor of the TF-factor (F)VIIa-Xa coagulation initiation complex which blocks primary tumor growth and angiogenesis in glioblastoma and melanoma models.

METHODS

In this study we address the anti-tumor effects of Ixolaris in TF-VIIa-PAR2 signaling-dependent breast cancer models, a xenograft model of highly aggressive human MDA-MB-231 mfp cells and a syngeneic model of PAR2-deficient and replete PyMT mouse mammary carcinoma cells.

RESULTS

Ixolaris potently inhibited the procoagulant activity of human MDA-MB-231mfp or murine PyMT breast cancer cells. Ixolaris blocked signaling by the ternary TF-FVIIa-FXa complex, and, surprisingly, at higher concentrations also the binary TF-FVIIa complex on MDA-MB-231 cells. We show that Ixolaris interacts with certain residues in the human VIIa protease domain that are involved in PAR2 cleavage. In contrast to human VIIa, Ixolaris was a poor inhibitor of murine TF-FVIIa signaling and did not attenuate PAR2-dependent tumor growth in a syngeneic mouse model of breast cancer progression.

CONCLUSION

These data show that Ixolaris inhibits PAR2 cleavage specifically by human TF signaling complexes and suggest that Ixolaris may block tumor growth of human cell models with ectopic FVIIa expression through inhibition of direct TF-FVIIa-PAR2 signaling as well as its anticoagulant activity.

Tissue factor and cell signalling in cancer progression and thrombosis

The close link between coagulation activation and clinical cancer is well established and recent progress has defined underlying molecular pathways by which tumour cells interact with the haemostatic system to promote cancer progression. Tumour type-specific oncogenic transformations cause constitutive and hypoxia-dependent upregulation of tissue factor (TF) in cancer cells, but TF expressed by vascular, stromal and inflammatory cells also contributes to the procoagulant character of the tumour microenvironment. A growing body of genetic and pharmacological evidence implicates signalling by protease activated receptors (PARs) and specifically by tumour cell-expressed TF-VIIa-PAR2 in the induction of an array of proangiogenic and immune modulating cytokines, chemokines and growth factors. Specific inhibition of this pathway results in attenuated tumour growth and angiogenesis. PARs are increasingly recognised as targets for proteases outside the coagulation system and emerging evidence indicates that alternative protease signalling pathways synergise with the coagulation system to promote tumour growth, angiogenesis and metastasis. The elucidation of new therapeutic targets in tumour-promoting protease signalling pathways requires new diagnostic approaches to identify patients that will benefit from tailored therapy targeting procoagulant or signalling aspects of the TF pathway.

Ixolaris, a tissue factor inhibitor, blocks primary tumor growth and angiogenesis in a glioblastoma model

BACKGROUND

The expression levels of the clotting initiator protein Tissue Factor (TF) correlate with vessel density and the histological malignancy grade of glioma patients. Increased procoagulant tonus in high grade tumors (glioblastomas) also indicates a potential role for TF in progression of this disease, and suggests that anticoagulants could be used as adjuvants for its treatment.

OBJECTIVES

We hypothesized that blocking of TF activity with the tick anticoagulant Ixolaris might interfere with glioblastoma progression.

METHODS AND RESULTS

TF was identified in U87-MG cells by flow-cytometric and functional assays (extrinsic tenase). In addition, flow-cytometric analysis demonstrated the exposure of phosphatidylserine in the surface of U87-MG cells, which supported the assembly of intrinsic tenase (FIXa/FVIIIa/FX) and prothrombinase (FVa/FXa/prothrombin) complexes, accounting for the production of FXa and thrombin, respectively. Ixolaris effectively blocked the in vitro TF-dependent procoagulant activity of the U87-MG human glioblastoma cell line and attenuated multimolecular coagulation complexes assembly. Notably, Ixolaris inhibited the in vivo tumorigenic potential of U87-MG cells in nude mice, without observable bleeding. This inhibitory effect of Ixolaris on tumor growth was associated with downregulation of VEGF and reduced tumor vascularization.

CONCLUSION

Our results suggest that Ixolaris might be a promising agent for anti-tumor therapy in humans.