Targeting the GLI family of transcription factors for the development of anti-cancer drugs

Recent progress in the development of nanomaterials targeting multiple cancer metabolic pathways: a review of mechanistic approaches for cancer treatment

Cancer is a very heterogeneous disease, and uncontrolled cell division is the main characteristic of cancer. Cancerous cells need a high nutrition intake to enable aberrant growth and survival. To do so, cancer cells modify metabolic pathways to produce energy and anabolic precursors and preserve redox balance. Due to the importance of metabolic pathways in tumor growth and malignant transformation, metabolic pathways have also been given promising perspectives for cancer treatment, providing more effective treatment strategies, and target-specific with minimum side effects. Metabolism-based therapeutic nanomaterials for targeted cancer treatment are a promising option. Numerous types of nanoparticles (NPs) are employed in the research and analysis of various cancer therapies. The current review focuses on cutting-edge strategies and current cancer therapy methods based on nanomaterials that target various cancer metabolisms. Additionally, it highlighted the primacy of NPs-based cancer therapies over traditional ones, the challenges, and the future potential.

Targeting the Hedgehog pathway with novel Gli1 hydrophobic tagging degraders

The Hedgehog/Glioma-associated oncogene (Hh/Gli) signaling pathway plays an essential role in embryonic development and tissue homeostasis. Aberrant regulation of this pathway has been linked to various human malignancies. Gli1, the downstream transcription factor of the Hh pathway, is the ultimate effector of the canonical Hh pathway and has been identified as a common regulator of several tumorigenic pathways prevalent in Hh-independent cancers. Thus Gli1 represents a unique and promising drug target for a wide range of cancers. However, the identification and development of small molecules that directly target Gli1 protein have progressed slowly, due to an insufficient efficacy and selectivity. Herein, we developed novel small-molecule Gli1 degraders based on the hydrophobic tagging (HyT) strategy. The Gli1 HyT degrader 8e potently inhibited the proliferation of Gli1-overexpressed HT29 colorectal cancer cells, induced Gli1 degradation with a DC50 value of 5.4 μM in HT29 and achieved 70% degradation at 7.5 μM in MEFPTCH1-/- and MEFSUFU-/-cell lines, via proteasome pathway. Compared to the canonical Hh antagonist Vismodegib, 8e exhibited much stronger potency in suppressing the mRNA expression of Hh target genes in Hh-overactivated MEFPTCH1-/- and Vismodegib resistant MEFSUFU-/- cells. Our study provides small molecule Gli1 degraders effectively interfering with both canonical and noncanonical Hh signaling and overcoming current Smoothened (SMO) antagonists resistance, which might pave a new avenue for developing therapeutic modalities targeting Hh/Gli1 signaling pathway.

Inhibition of GLI Transcriptional Activity and Prostate Cancer Cell Growth and Proliferation by DAX1

The Hedgehog (Hh) signaling pathway plays an essential role in the initiation and progression of prostate cancer. This is mediated by transcriptional factors belonging to the GLI (glioma-associated oncogene) family, which regulate downstream targets to drive prostate cancer progression. The activity of GLI proteins is tightly controlled by a range of mechanisms, including molecular interactions and post-translational modifications. In particular, mitogenic and oncogenic signaling pathways have been shown to regulate GLI protein activity independently of upstream Hh pathway signaling. Identifying GLI protein regulators is critical for the development of targeted therapies that can improve patient outcomes. This study aimed to identify a novel protein that directly regulates the activity of GLI transcription factors in prostate cancer. We performed gene expression, cellular analyses, and reporter assays to demonstrate that DAX1 (dosage-sensitive sex reversal adrenal hypoplasia congenital critical region on X chromosome, gene 1) interacts with GLI1 and GLI2, the master regulators of Hh signaling. Interestingly, DAX1 overexpression significantly inhibited Hh signaling by reducing GLI1 and GLI2 activity, prostate cancer cell proliferation, and viability. Our results shed light on a novel regulatory mechanism of Hh signaling in prostate cancer cells. The interaction between DAX1 and GLI transcription factors provides insight into the complex regulation of Hh signaling in prostate cancer. Given the importance of Hh signaling in prostate cancer progression, targeting DAX1-GLI interactions may represent a promising therapeutic approach against prostate cancer. Overall, this study provides new insights into the regulation of the Hh pathway and its role in prostate cancer progression. The findings suggest that DAX1 could serve as a potential therapeutic target for the treatment of prostate cancer.

The Role of Hedgehog Signaling in the Melanoma Tumor Bone Microenvironment

A crucial regulator in melanoma progression and treatment resistance is tumor microenvironments, and Hedgehog (Hh) signals activated in a tumor bone microenvironment are a potential new therapeutic target. The mechanism of bone destruction by melanomas involving Hh/Gli signaling in such a tumor microenvironment is unknown. Here, we analyzed surgically resected oral malignant melanoma specimens and observed that Sonic Hedgehog, Gli1, and Gli2 were highly expressed in tumor cells, vasculatures, and osteoclasts. We established a tumor bone destruction mouse model by inoculating B16 cells into the bone marrow space of the right tibial metaphysis of 5-week-old female C57BL mice. An intraperitoneal administration of GANT61 (40 mg/kg), a small-molecule inhibitor of Gli1 and Gli2, resulted in significant inhibition of cortical bone destruction, TRAP-positive osteoclasts within the cortical bone, and endomucin-positive tumor vessels. The gene set enrichment analysis suggested that genes involved in apoptosis, angiogenesis, and the PD-L1 expression pathway in cancer were significantly altered by the GANT61 treatment. A flow cytometry analysis revealed that PD-L1 expression was significantly decreased in cells in which late apoptosis was induced by the GANT61 treatment. These results suggest that molecular targeting of Gli1 and Gli2 may release immunosuppression of the tumor bone microenvironment through normalization of abnormal angiogenesis and bone remodeling in advanced melanoma with jaw bone invasion.

8-Hydroxyquinoline derivatives suppress GLI1-mediated transcription through multiple mechanisms

Aberrant activation of the Hedgehog (Hh) signaling pathway has been observed in various human malignancies. Glioma-associated oncogene transcription factor 1 (GLI1) is the ultimate effector of the canonical Hh pathway and has also been identified as a common regulator of several tumorigenic pathways prevalent in Hh-independent cancers. The anti-cancer potential of GLI1 antagonism with small molecule inhibitors has demonstrated initial promise; however, the continued development of GLI1 inhibitors is still needed. We previously identified a scaffold containing an 8-hydroxyquinoline as a promising lead GLI1 inhibitor (compound 1). To further develop this scaffold, we performed a systematic structure-activity relationship study to map the structural requirements of GLI1 inhibition by this chemotype. A series of biophysical and cellular experiments identified compound 39 as an enhanced GLI1 inhibitor with improved activity. In addition, our studies on this scaffold suggest a potential role for SRC family kinases in regulating oncogenic GLI1 transcriptional activity.

Expanding the spectrum of GLI1-altered mesenchymal tumors-A high-grade uterine sarcoma harboring a novel PAMR1::GLI1 fusion and literature review of GLI1-altered mesenchymal neoplasms of the gynecologic tract

GLI1-altered mesenchymal tumors comprise a group of seemingly unrelated entities, including pericytoma with t(7;12) translocation, plexiform fibromyxoma, gastroblastoma, malignant epithelioid neoplasm with GLI1 rearrangements, and GLI1-amplified mesenchymal neoplasms. Herein, we report a high-grade uterine sarcoma harboring a novel PAMR1::GLI1 fusion and present a literature review of GLI1-altered mesenchymal neoplasms of the gynecologic tract. A 57-year-old female presented with an abdomino-pelvic mass, felt since a decade prior. Magnetic resonance imaging showed a heterogenous myometrial mass extending beyond the serosa. The patient underwent oncologic surgical resection. Gross examination revealed a perforated multi-nodular uterine tumor (21 cm) with a firm white and soft fleshy cut surface, featuring hemorrhage and necrosis. The tumor was morphologically heterogenous, disclosing frankly sarcomatous areas composed of pleomorphic spindle and focally epithelioid cells, intermingled with a component of low-grade spindle cells arranged in fascicles. There was a rich vascular network and zones of necrosis with peripheral amianthoid-like collagen plaques. Lymphovascular invasion and metastasis to lymph nodes and omentum were present. The tumor was immunopositive for CD10 and cyclinD1, and negative for cytokeratins, myogenic, melanotic, and hormonal markers. ArcherTM Fusion Sarcoma Assay detected PAMR1(exon1)::GLI1(exon4) fusion, confirmed on RT-PCR and Sanger sequencing. The patient received chemo-radiotherapy, however, developed metastatic recurrence and demised 18 months post-surgery. Altogether, this is a rare and diagnostically challenging case of a uterine sarcoma harboring a novel GLI1 fusion. Emerging GLI/Hedgehog inhibitors provide clinical relevance to recognizing these tumors in modern pathology.

Arsenic Trioxide Triggers Apoptosis of Metastatic Oral Squamous Cells Carcinoma with Concomitant Downregulation of GLI1 in Hedgehog Signaling

Given the lack of advances in Oral Squamous Cell Carcinoma (OSCC) therapy in recent years, pharmacological strategies to block OSCC-related signaling pathways have gained prominence. The present study aimed to evaluate the therapeutic potential of Arsenic Trioxide (ATO) concerning its antitumoral effects and the inhibition of the Hedgehog (HH) pathway in OSCC. Initially, ATO cytotoxicity was assessed in a panel of cell lines. Cell viability, cell cycle, death patterns, and cell morphology were analyzed, as well as the effect of ATO on the expression of HH pathway components. After the cytotoxic assay, HSC3 cells were chosen for all in vitro assays. ATO increased apoptotic cell death and nuclear fragmentation in the sub-G1 cell cycle phase and promoted changes in cell morphology. In addition, the reduced expression of GLI1 indicated that ATO inhibits HH activity. The present study provides evidence of ATO as an effective cytotoxic drug for oral cancer treatment in vitro.

Analysis of Primary Cilium Expression and Hedgehog Pathway Activation in Mesothelioma Throws Back Its Complex Biology

The primary cilium (PC) is a sensory organelle present on the cell surface, modulating the activity of many pathways. Dysfunctions in the PC lead to different pathologic conditions including cancer. Hedgehog signaling (Hh) is regulated by PC and the loss of its control has been observed in many cancers, including mesothelioma. Malignant pleural mesothelioma (MPM) is a fatal cancer of the pleural membranes with poor therapeutic options. Recently, overexpression of the Hh transcriptional activator GL1 has been demonstrated to be associated with poor overall survival (OS) in MPM. However, unlike other cancers, the response to G-protein-coupled receptor smoothened (SMO)/Hh inhibitors is poor, mainly attributable to the lack of markers for patient stratification. For all these reasons, and in particular for the role of PC in the regulation of Hh, we investigated for the first time the status of PC in MPM tissues, demonstrating intra- and inter-heterogeneity in its expression. We also correlated the presence of PC with the activation of the Hh pathway, providing uncovered evidence of a PC-independent regulation of the Hh signaling in MPM. Our study contributes to the understanding MPM heterogeneity, thus helping to identify patients who might benefit from Hh inhibitors.

Canonical Hedgehog Pathway and Noncanonical GLI Transcription Factor Activation in Cancer

The Hedgehog signaling pathway is one of the fundamental pathways required for development and regulation of postnatal regeneration in a variety of tissues. The pathway has also been associated with cancers since the identification of a mutation in one of its components, PTCH, as the cause of Basal Cell Nevus Syndrome, which is associated with several cancers. Our understanding of the pathway in tumorigenesis has expanded greatly since that initial discovery over two decades ago. The pathway has tumor-suppressive and oncogenic functions depending on the context of the cancer. Furthermore, noncanonical activation of GLI transcription factors has been reported in a number of tumor types. Here, we review the roles of canonical Hedgehog signaling pathway and noncanonical GLI activation in cancers, particularly epithelial cancers, and discuss an emerging concept of the distinct outcomes that these modes have on cancer initiation and progression.

GLI1-altered epithelioid soft tissue tumor: A newly described entity with a predilection for the tongue

A novel subset of epithelioid soft tissue tumors with GLI1 gene fusions or amplifications has recently been characterized. Histologically, these tumors typically exhibit multinodular or plexiform growth of ovoid, round to epithelioid neoplastic cells, with a distinctive nested architecture separated by a rich delicate arborizing vascular network. The immunoprofile is variable and nonspecific, indicating no definitive line of differentiation. GLI1-altered epithelioid soft tissue tumor is considered to be a low-grade sarcoma; however, with a limited number of cases reported, the biologic behavior of this entity is unclear. Interestingly, these tumors frequently occur in the head and neck, with a clear predilection for the tongue. To date, 11 cases of lingual GLI1-altered epithelioid soft tissue tumors have been reported in the English literature, and none showed evidence of recurrence or metastasis. Herein, we report an additional case of lingual GLI1-altered epithelioid soft tissue tumor harboring GLI1 fusion in a 56-year-old man with regional nodal metastasis and distant metastasis to increase the awareness of this entity among oral pathologists and clinicians. An accumulation of similar cases is mandatory to clarify biological behaviors and also for the development of new therapeutic strategies.

GLI1 Gene Alterations in Neoplasms of the Genitourinary and Gynecologic Tract

We report 4 neoplasms of the kidney (2 cases) and uterus (2 cases) harboring rearrangements or amplifications of the GLI1 gene, which because of their unusual clinical presentation, morphology, and immunoprofile mimicked other neoplasms, causing significant diagnostic challenge. The neoplasms occurred in 4 female patients ages 33 to 88 years. Histologically they all demonstrated nodular growth, solid architecture, bland epithelioid to ovoid-spindle cells with pale cytoplasm set in a variably myxoid or hyalinized stroma. One uterine tumor also demonstrated a focal round cell pattern, while another demonstrated focal pleomorphism. Unlike most previously reported neoplasms with these genetic abnormalities, the neoplasms in the current series were negative for S100 protein and minimally reactive for actin. All labeled for CD10 and cyclin D1, while 2 labeled for estrogen receptor and BCOR and 1 labeled for desmin, raising consideration of endometrial stromal sarcoma, myxoid leiomyosarcoma, metastatic breast carcinoma, and glomus tumor. One renal neoplasm demonstrated a GLI1-FOXO4 gene fusion and the other harbored a GLI1 gene rearrangement (unknown partner). The 2 uterine neoplasms exhibited GLI1 gene amplifications. GLI1-altered neoplasms (particularly those with GLI1 amplification) show variable morphology and lack a consistent immunophenotype, and thus may trigger diagnostic challenges which can be resolved by molecular testing.

Cellular Mechanisms of Liver Fibrosis

The liver is a central organ in the human body, coordinating several key metabolic roles. The structure of the liver which consists of the distinctive arrangement of hepatocytes, hepatic sinusoids, the hepatic artery, portal vein and the central vein, is critical for its function. Due to its unique position in the human body, the liver interacts with components of circulation targeted for the rest of the body and in the process, it is exposed to a vast array of external agents such as dietary metabolites and compounds absorbed through the intestine, including alcohol and drugs, as well as pathogens. Some of these agents may result in injury to the cellular components of liver leading to the activation of the natural wound healing response of the body or fibrogenesis. Long-term injury to liver cells and consistent activation of the fibrogenic response can lead to liver fibrosis such as that seen in chronic alcoholics or clinically obese individuals. Unidentified fibrosis can evolve into more severe consequences over a period of time such as cirrhosis and hepatocellular carcinoma. It is well recognized now that in addition to external agents, genetic predisposition also plays a role in the development of liver fibrosis. An improved understanding of the cellular pathways of fibrosis can illuminate our understanding of this process, and uncover potential therapeutic targets. Here we summarized recent aspects in the understanding of relevant pathways, cellular and molecular drivers of hepatic fibrosis and discuss how this knowledge impact the therapy of respective disease.