The FACT inhibitor CBL0137 Synergizes with Cisplatin in Small-Cell Lung Cancer by Increasing NOTCH1 Expression and Targeting Tumor-Initiating Cells

Exploiting the DNA Damage Response for Prostate Cancer Therapy

Prostate cancers that progress despite androgen deprivation develop into castration-resistant prostate cancer, a fatal disease with few treatment options. In this review, we discuss the current understanding of prostate cancer subtypes and alterations in the DNA damage response (DDR) that can predispose to the development of prostate cancer and affect its progression. We identify barriers to conventional treatments, such as radiotherapy, and discuss the development of new therapies, many of which target the DDR or take advantage of recurring genetic alterations in the DDR. We place this in the context of advances in understanding the genetic variation and immune landscape of CRPC that could help guide their use in future treatment strategies. Finally, we discuss several new and emerging agents that may advance the treatment of lethal disease, highlighting selected clinical trials.

Histone chaperone SSRP1 is required for apoptosis inhibition and mitochondrial function in HCC via transcriptional promotion of TRAP1

Epigenetic regulation contributes to human health and disease, especially cancer, but the mechanisms of many epigenetic regulators remain obscure. Most research is focused on gene regulatory processes, such as mRNA translation and DNA damage repair, rather than the effects on biological functions like mitochondrial activity and oxidative phosphorylation. Here, we identified an essential role for the histone chaperone structure-specific recognition protein 1 (SSRP1) in mitochondrial oxidative respiration in hepatocellular carcinoma, and found that SSRP1 suppression led to mitochondrial damage and decreased oxidative respiration. Further, we focused on TNF receptor-associated protein 1 (TRAP1), the only member of the heat shock protein 90 (HSP90) family, which directly interacts with selected respiratory complexes and affects their stability and activity. We confirmed that SSRP1 downregulation caused a decrease in TRAP1 expression at both the mRNA and protein levels. A chromatin immunoprecipitation assay also showed that SSRP1 could deposit in the TRAP1 promoter region, indicating that SSRP1 maintains mitochondrial function and reactive oxygen species levels through TRAP1. Additionally, rescue experiments and animal experiments confirmed the mechanism of SSRP1 and TRAP1 interaction. In summary, we identified a new mechanism that connects mitochondrial respiration and apoptosis, via SSRP1.

CBL0137 activates ROS/BAX signaling to promote caspase-3/GSDME-dependent pyroptosis in ovarian cancer cells

Curaxin CBL0137 was designed to regulate p53 and nuclear factor-κB simultaneously and exhibits antitumor activity by inhibiting tumor cell proliferation and inducing apoptosis in multiple cancers. However, whether CBL0137 can induce pyroptosis has not yet been reported. This study demonstrated that CBL0137 induces caspase-3/gasdermin E (GSDME)-dependent pyroptosis via the reactive oxygen species (ROS)/BAX pathway. In ovarian cancer cells, CBL0137 inactivated the chromatin remodeling complex which could facilitate chromatin transcription, leading to the decreased transcription of antioxidant genes and oxidation and causing increased ROS levels. BAX was recruited on the mitochondrial membrane by mitochondrial ROS and induced the release of cytochrome c to cleave caspase-3. This led to the cleavage of the N-terminal of GSDME to form pores on the cell membrane and induced pyroptosis. Results of in vivo experiments revealed that CBL0137 also had anti-tumor effects on ovarian cancer cells in vivo. Our study outcomes reveal the mechanisms and targets of CBL0137 inducing pyroptosis in ovarian cancer cells and indicate that CBL0137 is a promising therapeutic agent for ovarian cancer.

Curaxin CBL0137 inhibits endothelial inflammation and atherogenesis via suppression of the Src-YAP signalling axis

BACKGROUND AND PURPOSE

Atherosclerotic vascular disease is the leading cause of mortality and morbidity worldwide. Our previous study uncovered that endothelium-specific knockdown of YAP suppresses atherogenesis, suggesting that YAP is a promising therapeutic target against atherosclerotic vascular disease. We established a drug screening platform, which aimed to identify new YAP inhibitors for anti-atherosclerotic treatment.

EXPERIMENTAL APPROACH

Drug screening was performed by a luciferase reporter gene assay. RNA sequencing was performed to acquire the transcriptomic profile of CBL0137-treated endothelial cells. We assessed and validated the inhibitory effect of CBL0137 on YAP activity and inflammatory response in HUVECs and HAECs. We evaluated the vasoprotective effect of CBL0137 in vivo against plaque formation in ApoE^-/- mice, using both disturbed flow-induced and chronic western diet-induced atherosclerotic models.

KEY RESULTS

We identified CBL0137 as a novel YAP inhibitor from an FDA drug library. CBL0137 inhibited YAP activity by restraining its phosphorylation at Y357. CBL0137 inhibited YAP activity to repress endothelial inflammation. Mechanistically, CBL0137 suppressed YAP phosphorylation at Y357 via the tyrosine-protein kinase Src. Furthermore, administration of CBL0137 ameliorated endothelial inflammation and the atherogenesis induced by disturbed flow and consumption of an atherogenic diet in ApoE^-/- mice.

CONCLUSION AND IMPLICATIONS

To our knowledge, this is the first study to identify CBL0137 as a novel YAP inhibitor. We have demonstrated that pharmacologically targeting YAP by CBL0137 inhibits atherogenesis. The present results suggest that CBL0137 holds promise as a new drug for the treatment of atherosclerotic vascular disease.

The FACT-targeted drug CBL0137 enhances the effects of rituximab to inhibit B-cell non-Hodgkin's lymphoma tumor growth by promoting apoptosis and autophagy

BACKGROUND

Aggressive B-cell non-Hodgkin's lymphoma (B-NHL) patients often develop drug resistance and tumor recurrence after conventional immunochemotherapy, for which new treatments are needed.

METHODS

We investigated the antitumor effects of CBL0137. In vitro, cell proliferation was assessed by CCK-8 and colony formation assay. Flow cytometry was performed to analyze cell cycle progression, apoptosis, mitochondrial depolarization, and reactive oxygen species (ROS) production. Autophagy was detected by transmission electron microscopy and mGFP-RFP-LC3 assay, while western blotting was employed to detect proteins involved in apoptosis and autophagy. RNA-sequencing was conducted to analyze the transcription perturbation after CBL0137 treatment in B-NHL cell lines. Finally, the efficacy and safety of CBL0137, rituximab, and their combination were tested in vivo.

RESULTS

CBL0137, a small molecule anticancer agent that has significant antitumor effects in B-NHL. CBL0137 sequesters the FACT (facilitates chromatin transcription) complex from chromatin to produce cytotoxic effects in B-NHL cells. In addition, we discovered novel anticancer mechanisms of CBL0137. CBL0137 inhibited human B-NHL cell proliferation by inducing cell cycle arrest in S phase via the c-MYC/p53/p21 pathway. Furthermore, CBL0137 triggers ROS generation and induces apoptosis and autophagy in B-NHL cells through the ROS-mediated PI3K/Akt/mTOR and MAPK signaling pathways. Notably, a combination of CBL0137 and rituximab significantly suppressed B-NHL tumor growth in subcutaneous models, consistent with results at the cellular level in vitro.

CONCLUSIONS

CBL0137 has potential as a novel approach for aggressive B-NHL, and its combination with rituximab can provide new therapeutic options for patients with aggressive B-NHL. Video Abstract.

Targeting Features of Curaxin CBL0137 on Hematological Malignancies In Vitro and In Vivo

The anticancer activity of Curaxin CBL0137, a DNA-binding small molecule with chromatin remodulating effect, has been demonstrated in different cancers. Herein, a comparative evaluation of CBL0137 activity was performed in respect to acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myeloid leukemia and multiple myeloma (MM) cultured in vitro. MTT assay showed AML and MM higher sensitivity to CBL0137's cytostatic effect comparatively to other hematological malignancy cells. Flow cytometry cell cycle analysis revealed an increase in subG1 and G2/M populations after CBL0137 cell treatment, but the prevalent type of arrest varied. Apoptosis activation by CBL0137 measured by Annexin-V/PI dual staining was more active in AML and MM cells. RT2 PCR array showed that changes caused by CBL0137 in signaling pathways involved in cancer pathogenesis were more intensive in AML and MM cells. On the murine model of AML WEHI-3, CBL0137 showed significant anticancer effects in vivo, which were evaluated by corresponding changes in spleen and liver. Thus, more pronounced anticancer effects of CBL0137 in vitro were observed in respect to AML and MM. Experiments in vivo also indicated the perspective of CBL0137 use for AML treatment. This in accordance with the frontline treatment approach in AML using epigenetic drugs.

CBL0137 impairs homologous recombination repair and sensitizes high-grade serous ovarian carcinoma to PARP inhibitors

BACKGROUND

High-grade serous ovarian carcinomas (HGSCs) are a heterogeneous subtype of epithelial ovarian cancers and include serous cancers arising in the fallopian tube and peritoneum. These cancers are now subdivided into homologous recombination repair (HR)-deficient and proficient subgroups as this classification impacts on management and prognosis. PARP inhibitors (PARPi) have shown significant clinical efficacy, particularly as maintenance therapy following response to platinum-based chemotherapy in BRCA-mutant or homologous recombination (HR)-deficient HGSCs in both the 1st and 2nd line settings. However, PARPi have limited clinical benefit in HR-proficient HGSCs which make up almost 50% of HGSC and improving outcomes in these patients is now a high priority due to the poor prognosis with ineffectiveness of the current standard of care. There are a number of potential lines of investigation including efforts in sensitizing HR-proficient tumors to PARPi. Herein, we aimed to develop a novel combination therapy by targeting SSRP1 using a small molecule inhibitor CBL0137 with PARPi in HR-proficient HGSCs.

EXPERIMENTAL DESIGN

We tested anti-cancer activity of CBL0137 monotherapy using a panel of HGSC cell lines and patient-derived tumor cells in vitro. RNA sequencing was used to map global transcriptomic changes in CBL0137-treated patient-derived HR-proficient HGSC cells. We tested efficacy of CBL0137 in combination with PARPi using HGSC cell lines and patient-derived tumor cells in vitro and in vivo.

RESULTS

We show that SSRP1 inhibition using a small molecule, CBL0137, that traps SSRP1 onto chromatin, exerts a significant anti-growth activity in vitro against HGSC cell lines and patient-derived tumor cells, and also reduces tumor burden in vivo. CBL0137 induced DNA repair deficiency via inhibition of the HR repair pathway and sensitized SSRP1-high HR-proficient HGSC cell lines and patient-derived tumor cells/xenografts to the PARPi, Olaparib in vitro and in vivo. CBL0137 also enhanced the efficacy of DNA damaging platinum-based chemotherapy in HGSC patient-derived xenografts.

CONCLUSION

Our findings strongly suggest that combination of CBL0137 and PARP inhibition represents a novel therapeutic strategy for HR-proficient HGSCs that express high levels of SSRP1 and should be investigated in the clinic.

Histone Chaperones and Digestive Cancer: A Review of the Literature

BACKGROUND

The global burden of digestive cancer is expected to increase. Therefore, crucial for the prognosis of patients with these tumors is to identify early diagnostic markers or novel therapeutic targets. There is accumulating evidence connecting histone chaperones to the pathogenesis of digestive cancer. Histone chaperones are now broadly defined as a class of proteins that bind histones and regulate nucleosome assembly. Recent studies have demonstrated that multiple histone chaperones are aberrantly expressed and have distinct roles in digestive cancers.

OBJECTIVE

The purpose of this review is to present the current evidence regarding the role of histone chaperones in digestive cancer, particularly their mechanism in the development and progression of esophageal, gastric, liver, pancreatic, and colorectal cancers. In addition, the prognostic significance of particular histone chaperones in patients with digestive cancer is discussed.

METHODS

According to PRISMA guidelines, we searched the PubMed, Embase, and MEDLINE databases to identify studies on histone chaperones and digestive cancer from inception until June 2022.

RESULTS

A total of 104 studies involving 21 histone chaperones were retrieved.

CONCLUSIONS

This review confirms the roles and mechanisms of selected histone chaperones in digestive cancer and suggests their significance as potential prognostic biomarkers and therapeutic targets. However, due to their non-specificity, more research on histone chaperones should be conducted in the future to elucidate novel strategies of histone chaperones for prognosis and treatment of digestive cancer.

Targeting the epigenetic processes to enhance antitumor immunity in small cell lung cancer

Dysregulation of the epigenetic processes, such as DNA methylation, histone modifications, and modulation of chromatin states, drives aberrant transcription that promotes initiation and progression of small cell lung cancer (SCLC). Accumulating evidence has proven crucial roles of epigenetic machinery in modulating immune cell functions and antitumor immune response. Epigenetics-targeting drugs such as DNA methyltransferase inhibitors, histone deacetylase inhibitors, and histone methyltransferase inhibitors involved in preclinical and clinical trials may trigger antitumor immunity. Herein, we summarize the impact of epigenetic processes on tumor immunogenicity and antitumor immune cell functions in SCLC. Furthermore, we review current clinical trials of epigenetic therapy against SCLC and the mechanisms of epigenetic inhibitors to boost antitumor immunity. Eventually, we discuss the opportunities of developing therapeutic regimens combining epigenetic agents with immunotherapy for SCLC.

The histone chaperone FACT: a guardian of chromatin structure integrity

The identification of FACT as a histone chaperone enabling transcription through chromatin in vitro has strongly shaped how its roles are envisioned. However, FACT has been implicated in essentially all aspects of chromatin biology, from transcription to DNA replication, DNA repair, and chromosome segregation. In this review, we focus on recent literature describing the role and mechanisms of FACT during transcription. We highlight the prime importance of FACT in preserving chromatin integrity during transcription and challenge its role as an elongation factor. We also review evidence for FACT's role as a cell-type/gene-specificregulator of gene expression and briefly summarize current efforts at using FACT inhibition as an anti-cancerstrategy.

Durable response to durvalumab-based immunochemotherapy in small-cell lung carcinoma transformation from EGFR-mutant non-small cell lung cancer: A case report

Combined small‐cell lung carcinoma (C‐SCLC) is small‐cell lung carcinoma (SCLC) with added non–small‐cell morphology. We report a case of epidermal growth factor receptor (EGFR) mutation‐positive C‐SCLC in an 84‐year‐old patient with metastatic brain lesions who developed intrinsic resistance to osimertinib, a tyrosine kinase inhibitor (TKI). The patient was diagnosed with small‐cell transformation of non–small‐cell lung carcinoma (NSCLC) and received 6 cycles of dose‐adjusted durvalumab with etoposide and carboplatin. In December 2021, the patient received the seventeenth cycle of maintenance durvalumab 19 months after diagnosis and showed continued treatment response and disease control. Comprehensive molecular profiling and repeated biopsies are recommended in NSCLC patients who progress on first‐line EGFR‐TKIs. Durvalumab in combination with chemotherapy appears to be beneficial for EGFR mutation‐positive C‐SCLC patients that are resistant to TKIs.

Subgroup-Specific Diagnostic, Prognostic, and Predictive Markers Influencing Pediatric Medulloblastoma Treatment

Medulloblastoma (MB) is the most common malignant central nervous system tumor in pediatric patients. Mainstay of therapy remains surgical resection followed by craniospinal radiation and chemotherapy, although limitations to this therapy are applied in the youngest patients. Clinically, tumors are divided into average and high-risk status on the basis of age, metastasis at diagnosis, and extent of surgical resection. However, technological advances in high-throughput screening have facilitated the analysis of large transcriptomic datasets that have been used to generate the current classification system, dividing patients into four primary subgroups, i.e., WNT (wingless), SHH (sonic hedgehog), and the non-SHH/WNT subgroups 3 and 4. Each subgroup can further be subdivided on the basis of a combination of cytogenetic and epigenetic events, some in distinct signaling pathways, that activate specific phenotypes impacting patient prognosis. Here, we delve deeper into the genetic basis for each subgroup by reviewing the extent of cytogenetic events in key genes that trigger neoplastic transformation or that exhibit oncogenic properties. Each of these discussions is further centered on how these genetic aberrations can be exploited to generate novel targeted therapeutics for each subgroup along with a discussion on challenges that are currently faced in generating said therapies. Our future hope is that through better understanding of subgroup-specific cytogenetic events, the field may improve diagnosis, prognosis, and treatment to improve overall quality of life for these patients.

The FAcilitates Chromatin Transcription (FACT) complex: Its roles in DNA repair and implications for cancer therapy

Genomic DNA in the nucleus is wrapped around nucleosomes, a repeating unit of chromatin. The nucleosome, consisting of octamer of core histones, is a barrier for several cellular processes that require access to the naked DNA. The FAcilitates Chromatin Transcription (FACT), a histone chaperone complex, is involved in nucleosome remodeling via eviction or assembly of histones during transcription, replication, and DNA repair. Increasing evidence suggests that FACT plays an important role in multiple DNA repair pathways including transcription-coupled nucleotide excision repair (TC-NER) of UV-induced damage, DNA single- and double-strand breaks (DSBs) repair, and base excision repair (BER) of oxidized or alkylated damaged bases. Further, studies have shown overexpression of FACT in multiple types of cancer and its association with drug resistance and patients' poor prognosis. In this review, we discuss how FACT is accumulated at the damage site and what functions it performs. We describe the known mechanisms by which FACT facilitates repair of different types of DNA damage. Further, we highlight the recent advances in a class of FACT inhibitors, called curaxins, which show promise as a new adjuvant therapy to sensitize multiple types of cancer to chemotherapy and radiation.

Kidney cancer biomarkers and targets for therapeutics: survivin (BIRC5), XIAP, MCL-1, HIF1α, HIF2α, NRF2, MDM2, MDM4, p53, KRAS and AKT in renal cell carcinoma

The incidence of renal cell carcinoma (RCC) is increasing worldwide with an approximate 20% mortality rate. The challenge in RCC is the therapy-resistance. Cancer resistance to treatment employs multiple mechanisms due to cancer heterogeneity with multiple genetic and epigenetic alterations. These changes include aberrant overexpression of (1) anticancer cell death proteins (e.g., survivin/BIRC5), (2) DNA repair regulators (e.g., ERCC6) and (3) efflux pump proteins (e.g., ABCG2/BCRP); mutations and/or deregulation of key (4) oncogenes (e.g., MDM2, KRAS) and/or (5) tumor suppressor genes (e.g., TP5/p53); and (6) deregulation of redox-sensitive regulators (e.g., HIF, NRF2). Foci of tumor cells that have these genetic alterations and/or deregulation possess survival advantages and are selected for survival during treatment. We will review the significance of survivin (BIRC5), XIAP, MCL-1, HIF1α, HIF2α, NRF2, MDM2, MDM4, TP5/p53, KRAS and AKT in treatment resistance as the potential therapeutic biomarkers and/or targets in RCC in parallel with our analized RCC-relevant TCGA genetic results from each of these gene/protein molecules. We then present our data to show the anticancer drug FL118 modulation of these protein targets and RCC cell/tumor growth. Finally, we include additional data to show a promising FL118 analogue (FL496) for treating the specialized type 2 papillary RCC.

Histone chaperone FACT complex inhibitor CBL0137 interferes with DNA damage repair and enhances sensitivity of medulloblastoma to chemotherapy and radiation

Medulloblastoma (MB) is a malignant pediatric brain tumor with a poor prognosis. Post-surgical radiation and cisplatin-based chemotherapy have been a mainstay of treatment, which often leads to substantial neurocognitive impairments and morbidity, highlighting the need for a novel therapeutic target to enhance the sensitivity of MB tumors to cytotoxic therapies. We performed a comprehensive study using a cohort of 71 MB patients' samples and pediatric MB cell lines and found that MB tumors have elevated levels of nucleosome remodeling FACT (FAcilitates Chromatin Transcription) complex and DNA repair enzyme AP-endonuclease1 (APE1). FACT interacts with APE1 and facilitates recruitment and acetylation of APE1 to promote repair of radiation and cisplatin-induced DNA damage. Further, levels of FACT and acetylated APE1 both are correlate strongly with MB patients' survival. Targeting FACT complex with CBL0137 inhibits DNA repair and alters expression of a subset of genes, and significantly improves the potency of cisplatin and radiation in vitro and in MB xenograft. Notably, combination of CBL0137 and cisplatin significantly suppressed MB tumor growth in an intracranial orthotopic xenograft model. We conclude that FACT complex promotes chemo-radiation resistance in MB, and FACT inhibitor CBL0137 can be used as a chemo-radiation sensitizer to augment treatment efficacy and reduce therapy-related toxicity in high-risk pediatric patients.

Overcoming anti-cancer drug resistance via restoration of tumor suppressor gene function

The cytotoxic anti-cancer drugs cisplatin, paclitaxel, doxorubicin, 5-fluorouracil (5-FU), as well as targeted drugs including imatinib, erlotinib, and nivolumab, play key roles in clinical cancer treatment. However, the frequent emergence of drug resistance severely comprosises their anti-cancer efficacy. A number of studies indicated that loss of function of tumor suppressor genes (TSGs) is involved in the development of cancer drug resistance, apart from decreased drug influx, increased drug efflux, induction of anti-apoptosis mechanisms, alterations in tumor microenvironment, drug compartmentalization, enhanced DNA repair and drug inactivation. TSGs are involved in the pathogenesis of tumor formation through regulation of DNA damage repair, cell apoptosis, autophagy, proliferation, cell cycle progression, and signal transduction. Our increased understanding of TSGs in the past decades demonstrates that gene mutation is not the only reason that leads to the inactivation of TSGs. Loss of function of TSGs may be based on the ubiquitin-proteasome pathway, epigenetic and transcriptional regualtion, post-translation modifications like phosphorylation as well as cellular translocation of TSGs. As the above processes can constitute"druggable targets", these mechanisms provide novel therapeutic approaches in targeting TSGs. Some small molecule compounds targeting these approaches re-activated TSGs and reversed cancer drug resistance. Along this vein, functional restoration of TSGs is a novel and promising approach to surmount cancer drug resistance. In the current review, we draw a scenario based on the role of loss of function of TSGs in drug resistance, on mechanisms leading to inactivation of TSGs and on pharmacological agents acting on these mechanisms to overcome cancer drug resistance. This review discusses novel therapeutic strategies targeting TSGs and offers possible modalities to conquer cancer drug resistance.

Exploring the Interaction of Curaxin CBL0137 with G-Quadruplex DNA Oligomers

Curaxins and especially the second-generation derivative curaxin CBL0137 have important antitumor activities in multiple cancers such as glioblastoma, melanoma and others. Although most of the authors suggest that their mechanism of action comes from the activation of p53 and inactivation of NF-kB by targeting FACT, there is evidence supporting the involvement of DNA binding in their antitumor activity. In this work, the DNA binding properties of curaxin CBL0137 with model quadruplex DNA oligomers were studied by ¹H NMR, CD, fluorescence and molecular modeling. We provided molecular details of the interaction of curaxin with two G-quadruplex structures, the single repeat of human telomere d(TTAGGGT)₄ and the c-myc promoter Pu22 sequence. We also performed ¹H and ³¹P NMR experiments were also performed in order to investigate the interaction with duplex DNA models. Our data support the hypothesis that the interaction of curaxin with G-quadruplex may provide a novel insight into the DNA-binding properties of CBL0137, and it will be helpful for the design of novel selective DNA-targeting curaxin analogues.

Inhibition of the FACT Complex Targets Aberrant Hedgehog Signaling and Overcomes Resistance to Smoothened Antagonists

Hedgehog signaling is aberrantly activated in hematologic malignancies and solid tumors, and targeting it is a promising therapeutic strategy against these cancers. Resistance to clinically available hedgehog-targeted Smoothened inhibitor (SMOi) drugs has become a critical issue in hedgehog-driven cancer treatment. Our previous studies identified inhibition of BET and CDK7 as two epigenetic/transcriptional-targeted therapeutic strategies for overcoming SMOi resistance, providing a promising direction for anti-hedgehog drug development. To uncover additional strategies for inhibiting aberrant hedgehog activity, here we performed CRISPR-Cas9 screening with an single-guide RNA library targeting epigenetic and transcriptional modulators in hedgehog-driven medulloblastoma cells, combined with tumor dataset analyses. Structure specific recognition protein 1 (SSRP1), a subunit of facilitates chromatin transcription (FACT) complex, was identified as a hedgehog-induced essential oncogene and therapeutic target in hedgehog-driven cancer. The FACT inhibitor CBL0137, which has entered clinical trials for cancer, effectively suppressed in vitro and in vivo growth of multiple SMOi-responsive and SMOi-resistant hedgehog-driven cancer models. Mechanistically, CBL0137 exerted anti-hedgehog activity by targeting transcription of GLI1 and GLI2, which are core transcription factors of the hedgehog pathway. SSRP1 bound the promoter regions of GLI1 and GLI2, while CBL0137 treatment substantially disrupted these interactions. Moreover, CBL0137 synergized with BET or CDK7 inhibitors to antagonize aberrant hedgehog pathway and growth of hedgehog-driven cancer models. Taken together, these results identify FACT inhibition as a promising epigenetic/transcriptional-targeted therapeutic strategy for treating hedgehog-driven cancers and overcoming SMOi resistance. SIGNIFICANCE: This study identifies FACT inhibition as an anti-hedgehog therapeutic strategy for overcoming resistance to Smoothened inhibitors and provides preclinical support for initiating clinical trials of FACT-targeted drug CBL0137 against hedgehog-driven cancers.

Single-cell transcriptome profiling reveals molecular heterogeneity in human umbilical cord tissue and culture-expanded mesenchymal stem cells

Human umbilical cord-derived mesenchymal stem/stromal cells (UMSCs) demonstrate great therapeutic potential in regenerative medicine. The use of UMSCs for clinical applications requires high quantity and good quality of cells usually by in vitro expansion. However, the heterogeneity and the characteristics of cultured UMSCs and the cognate human umbilical cord tissue at single-cell resolution remain poorly defined. In this study, we created a single-cell transcriptome profile of human umbilical cord tissue and the cognate culture-expanded UMSCs. Based on the inferred characteristics of cell clusters and trajectory analysis, we identified three subgroups in culture-expanded UMSCs and putative novel transcription factors (TFs) in regulating UMSC state transition. Further, putative ligand-receptor interaction analysis demonstrated that cellular interactions most frequently occurred in epithelial-like cells with other cell groups in umbilical cord tissue. Moreover, we dissected the transcriptomic differences of in vitro and in vivo subgroups and inferred the telomere-related molecules and pathways that might be activated in UMSCs for cell expansion in vitro. Our study provides a comprehensive and integrative study of the transcriptomics of human umbilical cord tissue and their cognate-cultured counterparts, which paves the way for a deeper understanding of cellular heterogeneity and offers fundamental biological insight of UMSCs-based cell therapy.

Curaxin-Induced DNA Topology Alterations Trigger the Distinct Binding Response of CTCF and FACT at the Single-Molecule Level

The candidate anticancer drug curaxins can insert into DNA base pairs and efficiently inhibit the growth of various cancers. However, how curaxins alter the genomic DNA structure and affect the DNA binding property of key proteins remains to be clarified. Here, we first showed that curaxin CBL0137 strongly stabilizes the interaction between the double strands of DNA and reduces DNA bending and twist rigidity simultaneously, by single-molecule magnetic tweezers. More importantly, we found that CBL0137 greatly impairs the binding of CTCF but facilitates trapping FACT on DNA. We revealed that CBL0137 clamps the DNA double helix that may induce a huge barrier for DNA unzipping during replication and transcription and causes the distinct binding response of CTCF and FACT on DNA. Our work provides a novel mechanical insight into CBL0137's anticancer mechanisms at the nucleic acid level.

Effective inhibition of MYC-amplified group 3 medulloblastoma by FACT-targeted curaxin drug CBL0137

Medulloblastoma (MB) is the most common malignant pediatric brain tumor that can be categorized into four major molecular subgroups. Group 3 MB with MYC amplification (MYCamp-G3-MB) has been shown to be highly aggressive and exhibited worst prognosis, indicating the need for novel effective therapy most urgently. A few epigenetic targeted therapeutic strategies have recently been proven to effectively treat preclinical models of MYCamp-G3-MB, including BET inhibition, HDAC inhibition and SETD8 inhibition, unveiling a promising direction for further investigation. In this study, we carried out systemic bioinformatic analyses of public-available MB datasets as well as functional genomic screening datasets of primary MYCamp-G3-MB lines to search for other potential therapeutic targets within epigenetic modulators. We identified SSRP1, a subunit of histone-chaperone FACT complex, to be the top drug target candidate as it is highly cancer-dependent in whole-genome CRISPR-Cas9 screening across multiple MYCamp-G3-MB lines; significantly upregulated in MYCamp-G3-MB compared to normal cerebellum and most of the rest MB subtypes; its higher expression is correlated with worse prognosis; and it has a blood-brain-barrier penetrable targeted drug that has entered early phase human clinical trials already. Then we utilized RNA-interference approach to verify the cancer-dependency of SSRP1 in multiple MYCamp-G3-MB lines and further confirmed the therapeutic efficacy of FACT-targeted curaxin drug CBL0137 on treating preclinical models of MYCamp-G3-MB in vitro and in vivo, including an orthotopic intracranial xenograft model. Mechanistically, transcriptome analyses showed CBL0137 preferentially suppressed cell-cycle and DNA-repair related biological processes. Moreover, it selectively disrupted transcription of MYC and NEUROD1, two critical oncogenic transcription factors of MYCamp-G3-MB, via depleting FACT complex from their promoter regions. In summary, our study demonstrates FACT-targeted CBL0137 works effectively on treating MYCamp-G3-MB, presenting another promising epigenetic-targeted therapeutic strategy against the most devastating form of MB.

CBL0137 increases the targeting efficacy of Rovalpituzumab tesirine against tumour-initiating cells in small cell lung cancer

Small cell lung cancer (SCLC) is characterised by high relapse rates. Tumour-initiating cells (TICs) are responsible for drug resistance and recurrence of cancer. Rovalpituzumab tesirine (Rova-T), a potent humanised antibody–drug conjugate, selectively targets delta-like protein 3, which is highly expressed in SCLC TICs. The experimental drug CBL0137 (CBL) inhibits the histone chaperone FACT (facilitates chromatin transcription), which is required for the expression of transcription factors that are essential for TIC maintenance. Rova-T and CBL each target SCLC TICs as single agents. However, acquired or intrinsic resistance to single agents is a major problem in cancer. Therefore, we investigated the potential effect of combining Rova-T and CBL in SCLC to eradicate TICs more effectively. Our preclinical studies report a novel and highly translatable therapeutic strategy of dual targeting TICs using Rova-T in combination with CBL to potentially increase survival of SCLC patients.

The small molecule drug CBL0137 increases the level of DNA damage and the efficacy of radiotherapy for glioblastoma

Glioblastoma (GBM) is an incurable brain tumor with inevitable recurrence. This is in part due to a highly malignant cancer stem cell (CSC) subpopulation of tumor cells that is particularly resistant to conventional treatments, including radiotherapy. Here we show that CBL0137, a small molecule anti-cancer agent, sensitizes GBM CSCs to radiotherapy. CBL0137 sequesters the FACT (facilitates chromatin transcription) complex to chromatin, resulting in cytotoxicity preferentially within tumor cells. We show that when combined with radiotherapy, CBL0137 inhibited GBM CSC growth and resulted in more DNA damage in the CSCs compared to irradiation or drug alone. Using an in vivo subcutaneous model, we showed that the frequency of GBM CSCs was reduced when tumors were pretreated with CBL0137 and then exposed to irradiation. Survival studies with orthotopic GBM models resulted in significantly extended survival for mice treated with combinatorial therapy. As GBM CSCs contribute to the inevitable recurrence in patients, targeting them is imperative. This work establishes a new treatment paradigm for GBM that sensitizes CSCs to irradiation and may ultimately reduce tumor recurrence.

Modeling Endothelialized Hepatic Tumor Microtissues for Drug Screening

Compared to various traditional 2D approaches, the scaffold-based 3D tumor models have emerged as an effective strategy to investigate the complex mechanisms behind cancer progression and responses to drug treatments, by providing biomimetic extracellular matrix and stromal-like microenvironments including the vascular elements. Herein, the development of a 3D endothelialized hepatic tumor microtissue model based on the fusion of multicellular aggregates of human hepatocellular carcinoma cells and human umbilical vein endothelial cells cocultured in poly(lactic-co-glycolic acid)-based porous microspheres (PLGA PMs) is reported. In contrast to the conventional 2D culture, the cells within the PLGA PMs exhibit significantly higher half-maximal inhibitory concentration values against anticancer drugs, including doxorubicin and cisplatin. Furthermore, the feasibility of coculturing other cell types, such as fibroblasts (L929) and HepG2 cells, is investigated. Together, the findings emphasize the significance of engineered 3D hepatic tumor microtissue models using PLGA PM-based multicellular aggregates for drug screening applications.

Detection of miR-155-5p and imaging lung cancer for early diagnosis: in vitro and in vivo study

Purpose

Currently, the routine screening program has insufficient capacity for the early diagnosis of lung cancer. Therefore, a type of chitosan-molecular beacon (CS-MB) probe was developed to recognize the miR-155-5p and image the lung cancer cells for the early diagnosis.

Methods

Based on the molecular beacon (MB) technology and nanotechnology, the CS-MB probe was synthesized self-assembly. There are four types of cells—three kinds of animal models and one type of histopathological sections of human lung cancer were utilized as models, including A549, SPC-A1, H446 lung cancer cells, tumor-initiating cells (TICs), subcutaneous and lung xenografts mice, and lox-stop-lox(LSL) K-ras G12D transgenic mice. The transgenic mice dynamically displayed the process from normal lung tissues to atypical hyperplasia, adenoma, carcinoma in situ, and adenocarcinoma. The different miR-155-5p expression levels in these cells and models were measured by quantitative real-time polymerase chain reaction (qRT-PCR). The CS-MB probe was used to recognize the miR-155-5p and image the lung cancer cells by confocal microscopy in vitro and by living imaging system in vivo.

Results

The CS-MB probe could be used to recognize the miR-155-5p and image the lung cancer cells significantly in these cells and models. The fluorescence intensity trends detected by the CS-MB probe were similar to the expression levels trends of miR-155 tested by qRT-PCR. Moreover, the fluorescence intensity showed an increasing trend with the tumor progression in the transgenic mice model, and the occurrence and development of lung cancer were dynamically monitored by the differen fluorescence intensity. In addition, the miR-155-5p in human lung cancer tissues could be detected by the miR-155-5p MB.

Conclusion

Both in vivo and in vitro experiments demonstrated that the CS-MB probe could be utilized to recognize the miR-155-5p and image the lung cancer cells. It provided a novel experimental and theoretical basis for the early diagnosis of the disease. Also, the histopathological sections of human lung cancer research laid the foundation for subsequent preclinical studies. In addition, different MBs could be designed to detect other miRNAs for the early diagnosis of other tumors.

A Translational Hepatic Artery Infusion (HAI) Model for Hepatocellular Carcinoma in Woodchucks

BACKGROUND

Woodchucks (Marmota monax) are a well-accepted animal model for the investigation of spontaneous hepatocellular carcinoma (HCC). As HCC tumors obtain nutrient blood supply exclusively from the hepatic artery, hepatic artery infusion (HAI) has been applied to HCC. However, there is a scarcity of experimental animal models to standardize drug regimens and examine novel agents. The purpose of this study was to establish an HAI model in woodchucks.

MATERIALS AND METHODS

HAI ports were placed in the gastroduodenal artery (GDA) of 11 woodchucks. The ports were infused with either a vehicle (dextrose 5% in water) or an experimental drug, CBL0137, once a week for 3 wk. Technical success rates, anatomical variation, morbidity and mortality, and tumor responses between groups were analyzed.

RESULTS

The GDA access was feasible and reproducible in all woodchucks (11/11). The average operation time was 95 ± 20 min with no increase in the levels of liver enzymes detected from either infusate. The most common morbidity of CBL0137 therapy was anorexia after surgery. One woodchuck died due to hemorrhage at the gallbladder removal site from hepatic coagulopathy. Significantly higher CBL0137 concentrations were measured in the liver compared with blood after each HAI. Tumor growth was suppressed after multiple CBL0137 HAI treatments which corresponded to greater T cell infiltration and increased tumor cell apoptosis.

CONCLUSIONS

HAI via GDA was a feasible and reproducible approach with low morbidity and mortality in woodchucks. The described techniques serve as a reliable platform for the identification and characterization of therapeutics for HCC.

The 3D Genome as a Target for Anticancer Therapy

The role of 3D genome organization in the precise regulation of gene expression is well established. Accordingly, the mechanistic connections between 3D genome alterations and disease development are becoming increasingly apparent. This opinion article provides a snapshot of our current understanding of the 3D genome alterations associated with cancers. We discuss potential connections of the 3D genome and cancer transcriptional addiction phenomenon as well as molecular mechanisms of action of 3D genome-disrupting drugs. Finally, we highlight issues and perspectives raised by the discovery of the first pharmaceutical strongly affecting 3D genome organization.

Interleukin 6 is increased in preclinical HNSCC models of acquired cetuximab resistance, but is not required for maintenance of resistance

The epidermal growth factor receptor inhibitor cetuximab is the only oncogene-targeted agent that has been FDA approved for the treatment of head and neck squamous cell carcinoma (HNSCC). Currently, there are no biomarkers used in the clinic to predict which HNSCC tumors will respond to cetuximab, and even in tumors that regress with treatment, acquired resistance occurs in the majority of cases. Though a number of mechanisms of acquired resistance to cetuximab have been identified in preclinical studies, no therapies targeting these resistance pathways have yet been effectively translated into the clinic. To address this unmet need, we examined the role of the cytokine interleukin 6 (IL-6) in acquired cetuximab resistance in preclinical models of HNSCC. We found that IL-6 secretion was increased in PE/CA-PJ49 cells that had acquired resistance to cetuximab compared to the parental cells from which they were derived. However, addition of exogenous IL-6 to parental cells did not promote cetuximab resistance, and inhibition of the IL-6 pathway did not restore cetuximab sensitivity in the cetuximab-resistant cells. Further examination of the IL-6 pathway revealed that expression of IL6R, which encodes a component of the IL-6 receptor, was decreased in cetuximab-resistant cells compared to parental cells, and that treatment of the cetuximab-resistant cells with exogenous IL-6 did not induce phosphorylation of signal transducer and activator of transcription 3, suggesting that the IL-6 pathway was functionally impaired in the cetuximab-resistant cells. These findings demonstrate that, even if IL-6 is increased in the context of cetuximab resistance, it is not necessarily required for maintenance of the resistant phenotype, and that targeting the IL-6 pathway may not restore sensitivity to cetuximab in cetuximab-refractory HNSCC.

Cancer Stem Cells: Powerful Targets to Improve Current Anticancer Therapeutics

A frequent observation in several malignancies is the development of resistance to therapy that results in frequent tumor relapse and metastasis. Much of the tumor resistance phenotype comes from its heterogeneity that halts the ability of therapeutic agents to eliminate all cancer cells effectively. Tumor heterogeneity is, in part, controlled by cancer stem cells (CSC). CSC may be considered the reservoir of cancer cells as they exhibit properties of self-renewal and plasticity and the capability of reestablishing a heterogeneous tumor cell population. The endowed resistance mechanisms of CSC are mainly attributed to several factors including cellular quiescence, accumulation of ABC transporters, disruption of apoptosis, epigenetic reprogramming, and metabolism. There is a current need to develop new therapeutic drugs capable of targeting CSC to overcome tumor resistance. Emerging in vitro and in vivo studies strongly support the potential benefits of combination therapies capable of targeting cancer stem cell-targeting agents. Clinical trials are still underway to address the pharmacokinetics, safety, and efficacy of combination treatment. This review will address the main characteristics, therapeutic implications, and perspectives of targeting CSC to improve current anticancer therapeutics.

Prevention of Colorectal Carcinogenesis by DNA-Binding Small-Molecule Curaxin CBL0137 Involves Suppression of Wnt Signaling

Chemoprevention is considered a valid approach to reduce the incidence of colorectal cancer, one of the most common malignancies worldwide. Here, we investigated the tumor-preventive activity of curaxin CBL0137. This compound represents a new class of nonmutagenic DNA-binding small molecules that alter chromatin stability and inhibit the function of the histone chaperone FACT. Among downstream effects of CBL0137 treatment are activation of p53 and type I interferons and inhibition of NFκB, HSF1, and MYC. In addition, our data show that in both human and mouse colorectal cancer cells in vitro, CBL0137 inhibits the APC/WNT/β-catenin signaling pathway, which plays a key role in colon carcinogenesis. Using quantitative RT-PCR and microarray hybridization, we have demonstrated decreased expression of multiple components and downstream targets of the WNT pathway in colon cancer cells treated with CBL0137. At the same time, CBL0137 induced expression of WNT antagonists. Inhibition of WNT signaling activity by CBL0137 was also confirmed by luciferase reporter assay. Tumor-preventive activity of CBL0137 in vivo was tested in a murine model of colorectal carcinogenesis induced by 1,2-dimethylhydrazine (DMH), which is known to involve WNT pathway dysregulation. After DMH subcutaneous treatment, mice were administered CBL0137 in drinking water. Efficacy of CBL0137 in suppressing development of colorectal cancer in this model was evidenced by reduced incidence of adenocarcinomas and adenomas in both males and females and decrease in tumor multiplicity. These data support the prospective use of CBL0137 in chemoprevention of colorectal cancer as well as of other malignances associated with activated WNT signaling.

Histone chaperone HIRA dictate proliferation vs differentiation of chronic myeloid leukemia cells

Abnormal proliferation and disrupted differentiation of hematopoietic progenitors mark leukemia. Histone cell cycle regulator A (HIRA), a histone chaperone, regulates hemogenic to hematopoietic transition involved in normal hematopoiesis. But, its role remains unexplored in leukemia, a case of dysregulated hematopoiesis. Here, the Cancer Cell Line Encyclopedia database analysis showed enhanced HIRA mRNA expression in cells of hematopoietic and lymphoid origin with maximal expression in the chronic myeloid leukemia (CML) cell line, K562. This observation was further endorsed by the induced expression of HIRA in CML patient samples compared to healthy individuals and Acute Myeloid Leukemia patients. Downregulation of HIRA in K562 cells displayed cell cycle arrest, loss in proliferation, presence of polyploidy with significant increase in CD41+ population thereby limiting proliferation but inducing differentiation of leukemia cells to megakaryocyte fate. Induced megakaryocyte differentiation of mouse Hira-knockout hematopoietic progenitors in vivo further confirmed the in vitro findings in leukemia cells. Molecular analysis showed the involvement of MKL1/GATA2/H3.3 axis in dictating differentiation of CML cells to megakaryocytes. Thus, HIRA could be exploited for differentiation induction therapy in CML and in chronic pathological conditions involving low platelet counts.

Characterising acquired resistance to erlotinib in non-small cell lung cancer patients

Introduction: The therapy of patients with lung adenocarcinoma has significantly changed after the discovery of epidermal growth factor receptor (EGFR) mutations. EGFR mutations occur in 10-15% of Caucasian lung cancer patients and are associated with favorable outcome to orally administered EGFR tyrosine kinase inhibitors (TKIs), like erlotinib. However, as soon as the tumor cells are under the pressure of the specific inhibitor, compensatory signaling pathways are activated and resistance emerges. Areas covered: In this review we will focus on the mechanisms of resistance to the first-generation EGFR TKI, erlotinib, and will mainly summarize the findings throughout the last 10 years in the field of EGFR-mutant lung cancer. Expert opinion: Widespread research has been performed and several mechanisms of resistance to EGFR TKIs, especially first- and second-generation, have been identified. Still, no adequate combinatory therapies have received regulatory approval for the treatment of EGFR-mutant patients at the time of resistance. The third-generation EGFR TKI, osimertinib has been approved for patients whose tumor has become resistant through the secondary T790M resistant EGFR mutation. The identification of the mechanisms of resistance and the application of the adequate therapy to each patient is still an unmet need.

Potent antileukemic activity of curaxin CBL0137 against MLL-rearranged leukemia

Around 10% of acute leukemias harbor a rearrangement of the MLL/KMT2A gene, and the presence of this translocation results in a highly aggressive, therapy-resistant leukemia subtype with survival rates below 50%. There is a high unmet need to identify safer and more potent therapies for MLL-rearranged (MLL-r) leukemia that can be combined with established chemotherapeutics to decrease treatment-related toxicities. The curaxin, CBL0137, has demonstrated nongenotoxic anticancer and chemopotentiating effects in a number of preclinical cancer models and is currently in adult Phase I clinical trials for solid tumors and hematological malignancies. The aim of our study was to investigate whether CBL0137 has potential as a therapeutic and chemopotentiating compound in MLL-r leukemia through a comprehensive analysis of its efficacy in preclinical models of the disease. CBL0137 decreased the viability of a panel of MLL-r leukemia cell lines (n = 12) and xenograft cells derived from patients with MLL-r acute lymphoblastic leukemia (ALL, n = 3) in vitro with submicromolar IC50s. The small molecule drug was well-tolerated in vivo and significantly reduced leukemia burden in a subcutaneous MV4;11 MLL-r acute myeloid leukemia model and in patient-derived xenograft models of MLL-r ALL (n = 5). The in vivo efficacy of standard of care drugs used in remission induction for pediatric ALL was also potentiated by CBL0137. CBL0137 exerted its anticancer effect by trapping Facilitator of Chromatin Transcription (FACT) into chromatin, activating the p53 pathway and inducing an Interferon response. Our findings support further preclinical evaluation of CBL0137 as a new approach for the treatment of MLL-r leukemia.

Future Options of Molecular-Targeted Therapy in Small Cell Lung Cancer

Lung cancer is the leading cause of cancer-related deaths worldwide. With a focus on histology, there are two major subtypes: Non-small cell lung cancer (NSCLC) (the more frequent subtype), and small cell lung cancer (SCLC) (the more aggressive one). Even though SCLC, in general, is a chemosensitive malignancy, relapses following induction therapy are frequent. The standard of care treatment of SCLC consists of platinum-based chemotherapy in combination with etoposide that is subsequently enhanced by PD-L1-inhibiting atezolizumab in the extensive-stage disease, as the addition of immune-checkpoint inhibition yielded improved overall survival. Although there are promising molecular pathways with potential therapeutic impacts, targeted therapies are still not an integral part of routine treatment. Against this background, we evaluated current literature for potential new molecular candidates such as surface markers (e.g., DLL3, TROP-2 or CD56), apoptotic factors (e.g., BCL-2, BET), genetic alterations (e.g., CREBBP, NOTCH or PTEN) or vascular markers (e.g., VEGF, FGFR1 or CD13). Apart from these factors, the application of so-called 'poly-(ADP)-ribose polymerases' (PARP) inhibitors can influence tumor repair mechanisms and thus offer new perspectives for future treatment. Another promising therapeutic concept is the inhibition of 'enhancer of zeste homolog 2' (EZH2) in the loss of function of tumor suppressors or amplification of (proto-) oncogenes. Considering the poor prognosis of SCLC patients, new molecular pathways require further investigation to augment our therapeutic armamentarium in the future.

Curaxin CBL0137 Exerts Anticancer Activity via Diverse Mechanisms

Chemotherapy with or without radiation remains the first choice for most cancers. However, intolerant side effects and conventional drug resistance restrict actual clinical efficacy. Curaxin CBL0137 is designed to regulate p53 and nuclear factor-κB simultaneously and to prevent the resistance caused by a single target. Functionally, CBL0137 exhibits an antitumor activity in multiple cancers, including glioblastoma, renal cell carcinoma, melanoma, neuroblastoma, and small cell lung cancer (SCLC). Mechanistically, CBL0137 is originally identified to act by facilitates chromatin transcription (FACT) complex. Further investigations reveal that several pathways, such as NOTCH1 and heat shock factor 1 (HSF1), are involved in the process. CBL0137 has been reported to target cancer stem cells (CSCs) and enhance chemotherapy/monotherapy efficacy. The translational advance of CBL0137 into clinical practice is expected to provide a promising future for cancer treatment.

[Medical treatment of small cell lung cancer: Can we leave the area of cisplatin-etoposide?]

Small cell lung cancer accounts for 14% of all lung cancers. It remains a major challenge for oncology as the progresses made in the past three decades are modest. After a rapid overview of current knowledge regarding somatic genomic alterations, this state-of-art addresses pathways to improve small-cell lung cancer outcome such as the targeting of DNA damage repair mechanisms firstly anti-PARPs, inhibitory molecules of EZH2, derepression of the NOTCH pathway, rovalbituzumab-tesirine, inhibition of serine/threonine Aurora A kinase, temozolomide and its dependence on methylation of the MGMT promoter. This first chapter suggests the beginning of precision medicine in small cell lung cancer. The last section focuses on the development of immuno-oncological agents and the information collected from phase 1 and 2 studies: the low intensity of PD-L1 tissue expression and the possible relationship of the activity of these agents as a function of tumor mutational burden are pointed out.