Gli1 contributes to cellular resistance to cisplatin through altered cellular accumulation of the drug

Defining the Role of GLI/Hedgehog Signaling in Chemoresistance: Implications in Therapeutic Approaches

Insight into cancer signaling pathways is vital in the development of new cancer treatments to improve treatment efficacy. A relatively new but essential developmental signaling pathway, namely Hedgehog (Hh), has recently emerged as a major mediator of cancer progression and chemoresistance. The evolutionary conserved Hh signaling pathway requires an in-depth understanding of the paradigm of Hh signaling transduction, which is fundamental to provide the necessary means for the design of novel tools for treating cancer related to aberrant Hh signaling. This review will focus substantially on the canonical Hh signaling and the treatment strategies employed in different studies, with special emphasis on the molecular mechanisms and combination treatment in regard to Hh inhibitors and chemotherapeutics. We discuss our views based on Hh signaling's role in regulating DNA repair machinery, autophagy, tumor microenvironment, drug inactivation, transporters, epithelial-to-mesenchymal transition, and cancer stem cells to promote chemoresistance. The understanding of this Achilles' Heel in cancer may improve the therapeutic outcome for cancer therapy.

Baicalin attenuates XRCC1-mediated DNA repair to enhance the sensitivity of lung cancer cells to cisplatin

Baicalin plays important roles in different types of cancer. A previous report showed that baicalin attenuates cisplatin resistance in lung cancer. However, its mechanism remains unclear. In this study, we investigated the effect and mechanism of baicalin on DNA repair and sensitivity of lung cancer cells to cisplatin. A549 and A549/DPP cells were treated with baicalin and cisplatin. A549/DPP cells were transfected with XRCC1 and siXRCC1. Cell viability and DNA damage were detected by MTT and comet assay. Apoptosis rate and cell cycle were detected by flow cytometry assay. The expressions of Bax, Bcl-2, and Cyclin D1 were detected by western blot. XRCC1 expression was detected by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blot. Baicalin and cisplatin decreased cell viability in A549 and A549/DPP cells in dose-dependent manner. Baicalin enhanced the effect of cisplatin on promoting apoptosis, arresting cell on S stage and triggering DNA damage accompanied with the upregulation of Bcl-2-associated X protein (Bax) and downregulation of B-cell lymphoma 2 (Bcl-2) and Cyclin D1 in A549/DPP cells. Moreover, baicalin promoted the inhibitory effect of cisplatin on XRCC1 expression in A549 and A549/DPP cells. However, the synthetic effects of baicalin and cisplatin on A549/DPP cells were partially inhibited by XRCC1 overexpression and promoted by XRCC1 knockdown. This study demonstrates that baicalin interferes with XRCC1-mediated cellar DNA repair to sensitize lung cancer cells to cisplatin.

PD-0332991 combined with cisplatin inhibits nonsmall cell lung cancer and reversal of cisplatin resistance

Background: Acquired resistance of chemotherapy, especially cisplatin, is a major challenge in lung cancer treatment. We conducted this study to examine whether a cyclin D kinase 4/6 (CDK4/6) inhibitor, PD 0332991, could reverse cisplatin resistance in human lung cancer cells. In addition, we explored the underlying mechanisms.

Method: We used CCK‐8 assay to got the IC50 of PD‐0332991 and cisplatin in A549 and A549/CDDP respectively. CCK‐8 assay, CalcuSyn 2.0 software, cell cycle distribution and apoptosis used to identify PD‐0332991 could reverse the acquired resistance of cisplatin. At last, western‐blot used to show the mechanism of PD‐0332991 enhances the effects of cisplatin.

Results: We found that PD‐0332991 potentiated cisplatin‐induced growth inhibition in both cisplatin‐sensitive (A549) and cisplatin‐resistant (A549/CDDP) cells via downregulation of the proliferation, induction of apoptosis (A549 increased to 7.06%; A549/CDDP increased to 7.03%), and G0/G1 cell cycle arrest (A549 increased to 9.15%; A549/CDDP increased to 49.92%). Western blot analysis revealed that PD‐0332991 enhance the effect of cisplatin through inhibit Rb‐E2Fs pathway.

Conclusions: These findings suggest that PD‐0332991 could reverse the acquired resistance of cisplatin in lung cancer cells and provide a novel treatment strategy for lung cancer patients with cisplatin resistance.

Overexpression of Fatty Acid 2-Hydroxylase is Associated with an Increased Sensitivity to Cisplatin by Ovarian Cancer and Better Prognoses

Background: Recent discoveries indicate that the enzyme fatty acid 2-hydroxylase (FA2H) is associated with biological behavior and can be used for outcome prediction in several types of cancers. Such relevancy, however, between FA2H and ovarian cancer is not clear. Therefore, we carried out this study to compare the expression of FA2H with the clinicopathological features of ovarian cancer. Methods: Using the Oncomine database, we examined the expression levels of the FA2H gene in ovarian cancer tissues and their adjacent noncancerous tissues that had been evaluated by quantitative reverse-transcription polymerase chain reaction (PCR) analyses. We performed Kaplan-Meier curve analyses for overall survival and progression-free survival. In addition, relationships between the FA2H expression levels and clinicopathological features of ovarian cancer were analyzed. Finally, FA2H small interfering RNAs (siRNAs) or negative control siRNAs were separately transfected into OVCAR-3 and SKOV-3 cells to explore the downstream effects. From these results, Gli1 expression was tested by real-time PCR, and the effects of FA2H expression levels on the sensitivity of ovarian cancer cells to cisplatin chemotherapy was evaluated using sulforhodamine B assays. Results: Compared with the adjacent tissues, FA2H was expressed at lower levels in the ovarian cancer tissues. In survival analyses, decreased FA2H was significantly associated with poorer survival outcome in multiple subtypes of ovarian cancer. In addition, FA2H expression was significantly associated with Fédération Internationale de Gynécologie et d'Obstétrique (FIGO) stage, differentiation, lymph node involvement, tumor size, ascites, CA125 levels, and pelvic involvement. Knockdown of FA2H expression by siRNAs in the OVCAR-3 and SKOV-3 cell lines reduced their sensitivity to cisplatin, via modulation of GLI Family Zinc Finger 1 (Gli1) gene expression. Conclusion: Our results demonstrate that FA2H is a biomarker for ovarian cancer and it may serve as a useful prognostic factor.

A Novel Therapeutic siRNA Nanoparticle Designed for Dual-Targeting CD44 and Gli1 of Gastric Cancer Stem Cells

Purpose

Gastric cancer stem cells (CSCs) are important for the initiation, growth, recurrence, and metastasis of gastric cancer, due to their chemo-resistance and indefinite proliferation. Herein, to eliminate gastric CSCs, we developed novel CSC-targeting glioma-associated oncogene homolog 1 (Gli1) small interfering RNA (siRNA) nanoparticles that are specifically guided by a di-stearoyl-phosphatidyl-ethanolamine- hyaluronic-acid (DSPE-HA) single-point conjugate, as an intrinsic ligand of the CD44 receptor. We refer to these as targeting Gli1 siRNA nanoparticles.

Methods

We used the reductive amination reaction method for attaching amine groups of DSPE to aldehydic group of hyaluronic acid (HA) at the reducing end, to synthesize the DSPE-HA single-point conjugate. Next, targeting Gli1 siRNA nanoparticles were prepared using the layer-by-layer assembly method. We characterized the stem cellular features of targeting Gli1 siRNA nanoparticles, including their targeting efficiency, self-renewal capacity, the migration and invasion capacity of gastric CSCs, and the penetration ability of 3D tumor spheroids. Next, we evaluated the therapeutic efficacy of the targeting Gli1 siRNA nanoparticles by using in vivo relapsed tumor models of gastric CSCs.

Results

Compared with the multipoint conjugates, DSPE-HA single-point conjugates on the surface of nanoparticles showed significantly higher binding affinities with CD44. The targeting Gli1 siRNA nanoparticles significantly decreased Gli1 protein expression, inhibited CSC tumor spheroid and colony formation, and suppressed cell migration and invasion. Furthermore, in vivo imaging demonstrated that targeting Gli1 siRNA nanoparticles accumulated in tumor tissues, showing significant antitumor recurrence efficacy in vivo.

Conclusion

In summary, our targeting Gli1 siRNA nanoparticles significantly inhibited CSC malignancy features by specifically blocking Hedgehog (Hh) signaling both in vitro and in vivo, suggesting that this novel siRNA delivery system that specifically eliminates gastric CSCs provides a promising targeted therapeutic strategy for gastric cancer treatment.

Fatty acid 2-hydroxylation inhibits tumor growth and increases sensitivity to cisplatin in gastric cancer

Background

Most gastric cancers are diagnosed at an advanced or metastatic stage with poor prognosis and survival rate. Fatty acid 2-hydroxylase (FA2H) with high expression in stomach generates chiral (R)-2-hydroxy FAs ((R)-2-OHFAs) and regulates glucose utilization which is important for cell proliferation and invasiveness. We hypothesized that FA2H impacts gastric tumor growth and could represent a novel target to improve gastric cancer therapy.

Methods

FA2H level in 117 human gastric tumors and its association with tumor growth, metastasis and overall survival were examined. Its roles and potential mechanisms in regulating tumor growth were studied by genetic and pharmacological manipulation of gastric cancer cells in vitro and in vivo.

Findings

FA2H level was lower in gastric tumor tissues as compared to surrounding tissues and associated with clinicopathologic status of patients, which were confirmed by analyses of multiple published datasets. FA2H depletion decreased tumor chemosensitivity, partially due to inhibition of AMPK and activation of the mTOR/S6K1/Gli1 pathway. Conversely, FA2H overexpression or treatment with (R)-2-OHFAs had the opposite effects. In line with these in vitro observations, FA2H knockdown promoted tumor growth with increased level of tumor Gli1 in vivo. Moreover, (R)-2-OHFA treatment significantly decreased Gli1 level in gastric tumors and enhanced tumor chemosensitivity to cisplatin, while alleviating the chemotherapy-induced weight loss in mice.

Interpretation

Our results demonstrate that FA2H plays an important role in regulating Hh signaling and gastric tumor growth and suggest that (R)-2-OHFAs could be effective as nontoxic wide-spectrum drugs to promote chemosensitivity.

Fund

Grants of NSF, NIH, and PAPD.

GLI1 overexpression promotes gastric cancer cell proliferation and migration and induces drug resistance by combining with the AKT-mTOR pathway

Hedgehog (HH) pathway significantly affected the pathogenesis of Gastric cancer (GC), but the multiple uncanonical HH pathways that are mediated by Zinc Finger protein GLI1 (GLI1) are still unclear. In the present work, we evaluated GLI1 and p-AKT expression in GC using immunohistochemistry (IHC) analysis. GLI1 and AKT specific shRNA was transfected into GC cell lines to investigate the cross-regulation between HH pathway and AKT-mTOR pathway. The effect of GLI1 and p-AKT on proliferation, migration, and drug resistance were examined. Moreover, a mouse xenograft model of GC was established to verify the role of GLI1 and p-AKT in promoting drug sensitivity in vivo. Our results suggested the clinicopathological factors and prognosis by the differential expression of GLI1 and p-AKT in GC patients. GLI1 was activated by the AKT-mTOR pathway. Co-expression of GLI1 and p-AKT was associated with cell viability, migration, and drug resistance and indicated a poor prognosis in GC patients. Agents targeted against both GLI1 and p-AKT may reverse drug-resistance and achieve better inhibition than agents targeted against a single molecule. There was a significant correlation between the high expression of GLI1 and p-AKT in GC. Additionally, our study confirmed the activity of the AKT-mTOR-GLI1 axis, which provided a new viable field for GC treatment.

Role of GLI Transcription Factors in Pathogenesis and Their Potential as New Therapeutic Targets

GLI transcription factors have important roles in intracellular signaling cascade, acting as the main mediators of the HH-GLI signaling pathway. This is one of the major developmental pathways, regulated both canonically and non-canonically. Deregulation of the pathway during development leads to a number of developmental malformations, depending on the deregulated pathway component. The HH-GLI pathway is mostly inactive in the adult organism but retains its function in stem cells. Aberrant activation in adult cells leads to carcinogenesis through overactivation of several tightly regulated cellular processes such as proliferation, angiogenesis, EMT. Targeting GLI transcription factors has recently become a major focus of potential therapeutic protocols.

Investigating the role of Hedgehog/GLI1 signaling in glioblastoma cell response to temozolomide

Resistance to chemotherapy substantially hinders successful glioblastoma (GBM) treatment, contributing to an almost 100% mortality rate. Resistance to the frontline chemotherapy, temozolomide (TMZ), arises from numerous signaling pathways that are deregulated in GBM, including Hedgehog (Hh) signaling. Here, we investigate suppression of Hh signaling as an adjuvant to TMZ using U87-MG and T98G cell lines as in vitro models of GBM. We found that silencing GLI1 with siRNA reduces cell metabolic activity by up to 30% in combination with TMZ and reduces multidrug efflux activity by 2.5-fold. Additionally, pharmacological GLI inhibition modulates nuclear p53 levels and decreases MGMT expression in combination with TMZ. While we surprisingly found that silencing GLI1 does not induce apoptosis in the absence of TMZ co-treatment, we discovered silencing GLI1 without TMZ co-treatment induces senescence as evidenced by a significant 2.3-fold increase in senescence associated β-galactosidase staining, and this occurs in a loss of PTEN-dependent manner. Finally, we show that GLI inhibition increases apoptosis in glioma stem-like cells by up to 6.8-fold in combination with TMZ, and this reduces the size and number of neurospheres grown from glioma stem-like cells. In aggregate, our data warrant the continued investigation of Hh pathway inhibitors as adjuvants to TMZ chemotherapy and highlight the importance of identifying signaling pathways that determine whether co-treatment will be successful.

Aspirin inhibits the SHH/GLI1 signaling pathway and sensitizes malignant glioma cells to temozolomide therapy

Aberrant activation of sonic hedgehog (SHH)/glioma-associated oncogene homolog 1 (GLI1) pathway plays an important role in the tumorigenicity of malignant glioma cells and resistance to temozolomide (TMZ). Here we investigated the aspirin's antineoplastic molecular route by targeting SHH/GLI1 pathway and examined the feasibility of aspirin combined with TMZ therapy. Western blot and quantitative real-time polymerase chain reaction (qRT-PCR) revealed that the activity of the SHH/GLI1 pathway was strongly inhibited by aspirin. Aspirin acted as the glioma growth-inhibitory and pro-apoptosis roles by inhibiting the SHH/GLI1 pathway and reprogramming the epithelial to mesenchymal transition (EMT). The immunofluorescence assay showed aspirin could prevent the nuclear translocation of GLI1 to inhibit its transcriptional regulation. The stable lentiviral overexpression of GLI1 reversed the DNA double strand breaks (DSBs) caused by the GANT61 and TMZ. Furthermore, aspirin combined with TMZ enhanced chemosensitivity and GLI1-induced chemoprotection was partly blocked by aspirin in vitro and in vivo. Collectively, aspirin has a therapeutic potential for SHH/GLI1 targeted therapy against glioma cells. Acquired activation of GLI1 protects glioma cells against TMZ therapy. Impairment of DNA DSBs repair activity might be involved in the route of aspirin-induced chemosensitivity. Combined aspirin with TMZ may be a promising strategy against malignant glioma.

Correlation of Gli1 and HER2 expression in gastric cancer: Identification of novel target

HER2 becomes the standard of care for guiding adjuvant treatment of gastric cancer with trastuzumab in recent years. However, the usage of this target agent is still limited because of the resistance to trastuzumab or the negative expression of HER2 in tumor tissues. The Gli1 and HER2 both play an important role in the pathogenesis of gastric cancer. However, the correlation of them is still unclear. Here we found Gli1 and HER2 are highly expressed in gastric cancer tissues, and they are positively related. Next, we found Gli1 positive patients live a shorter survival time no matter HER2 positive or negative. Furthermore, univariate and multivariate analysis revealed that venous invasion, HER2 expression, Gli1 expression were independent prognostic factors for the survival time in gastric cancer. In addition, suppressing the expression level of Gli1 can decrease the cell viability and migration ability in cells and subcutaneous tumors. Finally, we found that HER2 may regulate Gli1 by Akt-mTOR-p70S6K pathway. Inhibit of HER2 and SMO have synergistic effect on reduction of cell viability. In conclusion, Gli1 is a favorable prognostic indicator in gastric cancer. As a novel target, Gli1 worth further study, especially in Her2-targeted therapy-resistant cancers.

Nek2A/SuFu feedback loop regulates Gli-mediated Hedgehog signaling pathway

Suppressor of Fused (SuFu), one of the most conserved components of the Hedgehog (Hh) signaling, binds Gli transcription factors and impedes activation of target gene expression in mammalian cells. Despite the central importance of SuFu in the Hh pathway, little is known about SuFu regulation. In a previous study, we identified NIMA-related expressed kinase 2A (Nek2A) as a SuFu-interacting protein. Here, we show that Nek2A stabilizes SuFu through impairing ubiquitin/proteasome degradation of SuFu. In addition, Nek2A negatively regulates target genes of Hh signaling as well as Gli2 transcriptional activity. In turn, inhibition of Hh signaling by GANT61 diminishes mRNA and protein levels of Nek2A, and Hh agonist promotes transcription of NEK2A gene. Chromatin immunoprecipitation assays revealed that Gli1 and Gli2 directly bind to the promoter regions of NEK2A gene and induced its transcription. Thus, we uncovered one of the mechanisms by which Nek2A acts as a modulator of the Hh signaling pathway in the context of a novel negative-feedback loop, which may offer new insights into Gli-mediated Hh signaling regulation in development and human diseases.

Hedgehog inhibition enhances efficacy of radiation and cisplatin in orthotopic cervical cancer xenografts

BACKGROUND

The Hedgehog (Hh) pathway is upregulated in cervical cancer and associated with poor outcome. We explored the effects of Hh pathway inhibition in combination with RTCT in a patient derived orthotopic cervical cancer xenograft model (OCICx).

METHODS

5E1, a monoclonal antibody for SHH, or Sonidegib (LDE225), a clinical SMO inhibitor (Novartis) were added to RTCT. We investigated tumour growth delay, metastasis and GI toxicity using orthotopic cervical cancer xenografts models. The xenografts were treated with radiotherapy (15 × 2 Gy daily fractions over 3 weeks) and weekly cisplatin 4 mg kg^-1 concurrently, with or without 5E1 or Sonidegib (LDE225). The Hh inhibitors were administered by subcutaneous injection (5E1; 20 mg kg^-1 weekly for 3 weeks), or by oral gavage (Sonidegib; 60 mg kg^-1 daily for 3 weeks).

RESULTS

We observed that both Hh inhibitors administered with RTCT were well tolerated and showed increased tumour growth delay, and reduced metastasis, with no increase in acute GI-toxicity relative to RTCT alone.

CONCLUSIONS

Our data suggest Hh can be a valid therapeutic target in cervical cancer and supports data suggesting a potential therapeutic role for targeting Hh in patients undergoing RTCT. This warrants further investigation in clinical trials.

Combination of gambogic acid with cisplatin enhances the antitumor effects on cisplatin-resistant lung cancer cells by downregulating MRP2 and LRP expression

Cisplatin resistance is a main clinical problem of lung cancer therapy. Gambogic acid (GA) could prohibit the proliferation of a variety of human cancer cells. However, the effects of GA on cisplatin-resistant lung cancer are still unclear. The objective of the present study was to find out the antitumor effects of GA on cisplatin-resistant human lung cancer A549/DDP cells and further explore its underlying mechanisms. Cell Counting Kit-8 assay was used to observe the impacts of GA and/or cisplatin on the proliferation of lung cancer cells; flow cytometry was used to detect the effects of GA on cell cycle and apoptosis; Western blot was used to examine the effects of GA on the expression of lung resistance protein (LRP) and multidrug resistance-associated protein 2 (MRP2) protein in A549/DDP cells. Our results showed that GA dose- and time-dependently prohibited the proliferation and induced significant cell apoptosis in A549 and A549/DDP cells. GA also induced G0/G1 arrest in both A549/DDP and A549 cells. Moreover, GA upregulated protein expression level of cleaved caspase-3 and Bax and downregulated protein expression level of pro-caspase-9 and Bcl-2 in time- and dose-dependent way in A549/DDP cells. GA combined with cisplatin enhanced the cells apoptotic rate and reduced the cisplatin resistance index in A549/DDP cells. In addition, GA reduced the MRP2 and LRP protein expression level in A549/DDP cells. GA inhibits the proliferation, induces cell cycle arrest and apoptosis in A549/DDP cells. Combination of GA with cisplatin enhances the antitumor effects on cisplatin-resistant lung cancer cells by downregulating MRP2 and LRP expression.

Aberrant GLI1 Activation in DNA Damage Response, Carcinogenesis and Chemoresistance

The canonical hedgehog (HH) pathway is a multicomponent signaling cascade (HH, protein patched homolog 1 (PTCH1), smoothened (SMO)) that plays a pivotal role during embryonic development through activation of downstream effector molecules, namely glioma-associated oncogene homolog 1 (GLI1), GLI2 and GLI3. Activation of GLIs must be tightly regulated as they modulate target genes which control tissue patterning, stem cell maintenance, and differentiation during development. However, dysregulation or mutations in HH signaling leads to genomic instability (GI) and various cancers, for example, germline mutation in PTCH1 lead to Gorlin syndrome, a condition where patients develop numerous basal cell carcinomas and rarely rhabdomyosarcoma (RMS). Activating mutations in SMO have also been recognized in sporadic cases of medulloblastoma and SMO is overexpressed in many other cancers. Recently, studies in several human cancers have shown that GLI1 expression is independent from HH ligand and canonical intracellular signaling through PTCH and SMO. In fact, this aberrantly regulated GLI1 has been linked to several non-canonical oncogenic growth signals such as Kirsten rat sarcoma viral oncogene homolog (KRAS), avian myelocytomatosis virus oncogene cellular homolog (C-MYC), transforming growth factor β (TGFβ), wingless-type MMTV integration site family (WNT) and β-catenin. Recent studies from our lab and other independent studies demonstrate that aberrantly expressed GLI1 influences the integrity of several DNA damage response and repair signals, and if altered, these networks can contribute to GI and impact tumor response to chemo- and radiation therapies. Furthermore, the ineffectiveness of SMO inhibitors in clinical studies argues for the development of GLI1-specific inhibitors in order to develop effective therapeutic modalities to treat these tumors. In this review, we focus on summarizing current understanding of the molecular, biochemical and cellular basis for aberrant GLI1 expression and discuss GLI1-mediated HH signaling on DNA damage responses, carcinogenesis and chemoresistance.

The Impact of Hedgehog Signaling Pathway on DNA Repair Mechanisms in Human Cancer

Defined cellular mechanisms have evolved that recognize and repair DNA to protect the integrity of its structure and sequence when encountering assaults from endogenous and exogenous sources. There are five major DNA repair pathways: mismatch repair, nucleotide excision repair, direct repair, base excision repair and DNA double strand break repair (including non-homologous end joining and homologous recombination repair). Aberrant activation of the Hedgehog (Hh) signaling pathway is a feature of many cancer types. The Hh pathway has been documented to be indispensable for epithelial-mesenchymal transition, invasion and metastasis, cancer stemness, and chemoresistance. The functional transcription activators of the Hh pathway include the GLI proteins. Inhibition of the activity of GLI can interfere with almost all DNA repair types in human cancer, indicating that Hh/GLI functions may play an important role in enabling tumor cells to survive lethal types of DNA damage induced by chemotherapy and radiotherapy. Thus, Hh signaling presents an important therapeutic target to overcome DNA repair-enabled multi-drug resistance and consequently increase chemotherapeutic response in the treatment of cancer.