The BET bromodomain inhibitor ZEN-3365 targets the Hedgehog signaling pathway in acute myeloid leukemia

Targeting cancer hallmark vulnerabilities in hematologic malignancies by interfering with Hedgehog/GLI signaling

Understanding the genetic alterations, disrupted signaling pathways, and hijacked mechanisms in oncogene-transformed hematologic cells is critical for the development of effective and durable treatment strategies against liquid tumors. In this review, we focus on the specific involvement of the Hedgehog (HH)/GLI pathway in the manifestation and initiation of various cancer features in hematologic malignancies, including multiple myeloma, T- and B-cell lymphomas, and lymphoid and myeloid leukemias. By reviewing canonical and noncanonical, Smoothened-independent HH/GLI signaling and summarizing preclinical in vitro and in vivo studies in hematologic malignancies, we elucidate common molecular mechanisms by which HH/GLI signaling controls key oncogenic processes and cancer hallmarks such as cell proliferation, cancer stem cell fate, genomic instability, microenvironment remodeling, and cell survival. We also summarize current clinical trials with HH inhibitors and discuss successes and challenges, as well as opportunities for future combined therapeutic approaches. By providing a bird's eye view of the role of HH/GLI signaling in liquid tumors, we suggest that a comprehensive understanding of the general oncogenic effects of HH/GLI signaling on the formation of cancer hallmarks is essential to identify critical vulnerabilities within tumor cells and their supporting remodeled microenvironment, paving the way for the development of novel and efficient personalized combination therapies for hematologic malignancies.

BRD4 as a potential target for human papillomaviruses associated cancer

Around 99% of cervical cancer and 5%-10% of human cancer are associated with human papillomaviruses (HPV). Notably, the life-cycle of HPV begins by low-level infection of the basal cells of the stratified epithelium, where the viral genomes are replicated and passed on to the daughter proliferating basal cells. The production of new viral particles remains restricted to eventually differentiated cells. HPVs support their persistent infectious cycle by hijacking pivotal pathways and cellular processes. Bromodomain-containing protein 4 (BRD4) is one of the essential cellular factors involved in multiple stages of viral transcription and replication. In this review, we demonstrate the role of BRD4 in the multiple stages of HPV infectious cycle. Also, we provide an overview of the intense research about the cellular functions of BRD4, the mechanism of action of bromodomain and extra terminal inhibitors, and how it could lead to the development of antiviral/anticancer therapies.

Multiprotein GLI Transcriptional Complexes as Therapeutic Targets in Cancer

The Hedgehog signaling pathway functions in both embryonic development and adult tissue homeostasis. Importantly, its aberrant activation is also implicated in the progression of multiple types of cancer, including basal cell carcinoma and medulloblastoma. GLI transcription factors function as the ultimate effectors of the Hedgehog signaling pathway. Their activity is regulated by this signaling cascade via their mRNA expression, protein stability, subcellular localization, and ultimately their transcriptional activity. Further, GLI proteins are also regulated by a variety of non-canonical mechanisms in addition to the canonical Hedgehog pathway. Recently, with an increased understanding of epigenetic gene regulation, novel transcriptional regulators have been identified that interact with GLI proteins in multi-protein complexes to regulate GLI transcriptional activity. Such complexes have added another layer of complexity to the regulation of GLI proteins. Here, we summarize recent work on the regulation of GLI transcriptional activity by these novel protein complexes and describe their relevance to cancer, as such GLI regulators represent alternative and innovative druggable targets in GLI-dependent cancers.

Hedgehog/GLI signaling in hematopoietic development and acute myeloid leukemia-From bench to bedside

While the underlying genetic alterations and biology of acute myeloid leukemia (AML), an aggressive hematologic malignancy characterized by clonal expansion of undifferentiated myeloid cells, have been gradually unraveled in the last decades, translation into clinical treatment approaches has only just begun. High relapse rates remain a major challenge in AML therapy and are to a large extent attributed to the persistence of treatment-resistant leukemic stem cells (LSCs). The Hedgehog (HH) signaling pathway is crucial for the development and progression of multiple cancer stem cell driven tumors, including AML, and has therefore gained interest as a therapeutic target. In this review, we give an overview of the major components of the HH signaling pathway, dissect HH functions in normal and malignant hematopoiesis, and specifically elaborate on the role of HH signaling in AML pathogenesis and resistance. Furthermore, we summarize preclinical and clinical HH inhibitor studies, leading to the approval of the HH pathway inhibitor glasdegib, in combination with low-dose cytarabine, for AML treatment.