Targeting HOX-PBX interactions causes death in oral potentially malignant and squamous carcinoma cells but not normal oral keratinocytes

The Potential MicroRNA Diagnostic Biomarkers in Oral Squamous Cell Carcinoma of the Tongue

Oral squamous cell carcinoma (OSCC) of the tongue is a common type of head and neck malignancy with a poor prognosis, underscoring the urgency for early detection. MicroRNAs (miRNAs) have remarkable stability and are easily measurable. Thus, miRNAs may be a promising biomarker candidate among biomarkers in cancer diagnosis. Biomarkers have the potential to facilitate personalized medicine approaches by guiding treatment decisions and optimizing therapy regimens for individual patients. Utilizing data from The Cancer Genome Atlas, we identified 13 differentially expressed upregulated miRNAs in OSCC of the tongue. Differentially expressed miRNAs were analyzed by enrichment analysis to reveal underlying biological processes, pathways, or functions. Furthermore, we identified miRNAs associated with the progression of OSCC of the tongue, utilizing receiver operating characteristic analysis to evaluate their potential as diagnostic biomarkers. A total of 13 upregulated miRNAs were identified as differentially expressed in OSCC of the tongue. Five of these miRNAs had high diagnostic power. In particular, miR-196b has the potential to serve as one of the most effective diagnostic biomarkers. Then, functional enrichment analysis for the target gene of miR-196b was performed, and a protein-protein interaction network was constructed. This study assessed an effective approach for identifying miRNAs as early diagnostic markers for OSCC of the tongue.

HOXA9 transcription factor is a double-edged sword: from development to cancer progression

The HOXA9 transcription factor serves as a molecular orchestrator in cancer stemness, epithelial-mesenchymal transition (EMT), metastasis, and generation of the tumor microenvironment in hematological and solid malignancies. However, the multiple modes of regulation, multifaceted functions, and context-dependent interactions responsible for the dual role of HOXA9 as an oncogene or tumor suppressor in cancer remain obscure. Hence, unravelling its molecular complexities, binding partners, and interacting signaling molecules enables us to comprehend HOXA9-mediated transcriptional programs and molecular crosstalk. However, it is imperative to understand its central role in fundamental biological processes such as embryogenesis, foetus implantation, hematopoiesis, endothelial cell proliferation, and tissue homeostasis before designing targeted therapies. Indeed, it presents an enormous challenge for clinicians to selectively target its oncogenic functions or restore tumor-suppressive role without altering normal cellular functions. In addition to its implications in cancer, the present review also focuses on the clinical applications of HOXA9 in recurrence and drug resistance, which may provide a broader understanding beyond oncology, open new avenues for clinicians for accurate diagnoses, and develop personalized treatment strategies. Furthermore, we have also discussed the existing therapeutic options and accompanying challenges in HOXA9-targeted therapies in different cancer types.

PBX1 as a novel master regulator in cancer: Its regulation, molecular biology, and therapeutic applications

PBX1 is a critical transcription factor at the top of various cell fate-determining pathways. In cancer, PBX1 stands at the crossroads of multiple oncogenic signaling pathways and mediates responses by recruiting a broad repertoire of downstream targets. Research thus far has corroborated the involvement of PBX1 in cancer proliferation, resisting apoptosis, tumor-associated neoangiogenesis, epithelial-mesenchymal transition (EMT) and metastasis, immune evasion, genome instability, and dysregulating cellular metabolism. Recently, our understanding of the functional regulation of the PBX1 protein has advanced, as increasing evidence has depicted a regulatory network consisting of transcriptional, post-transcriptional, and post-translational levels of control mechanisms. Furthermore, accumulating studies have supported the clinical utilization of PBX1 as a prognostic or therapeutic target in cancer. Preliminary results showed that PBX1 entails vast potential as a targetable master regulator in the treatment of cancer, particularly in those with high-risk features and resistance to other therapeutic strategies. In this review, we will explore the regulation, protein-protein interactions, molecular pathways, clinical application, and future challenges of PBX1.

PBX1: a TALE of two seasons-key roles during development and in cancer

Pre-B cell leukemia factor 1 (PBX1) is a Three Aminoacid Loop Extension (TALE) homeodomain-containing transcription factor playing crucial roles in organ pattering during embryogenesis, through the formation of nuclear complexes with other TALE class and/or homeobox proteins to regulate target genes. Its contribution to the development of several organs has been elucidated mainly through the study of murine knockout models. A crucial role for human development has been recently highlighted through the discovery of different de novo pathogenic PBX1 variants in children affected by developmental defects. In the adult, PBX1 is expressed in selected tissues such as in the brain, in the gastro-intestinal and urinary systems, or in hematopoietic stem and progenitor cells, while in other organs is barely detectable. When involved in the t(1;19) chromosomal translocation it acts as an oncogene, since the resulting fusion protein drives pre-B cell leukemia, due to the induction of target genes not normally targeted by the native protein. Its aberrant expression has been associated to tumor development, progression, or therapy-resistance as in breast cancer, ovarian cancer or myeloproliferative neoplasm (MPN). On the other hand, in colorectal cancer PBX1 functions as a tumor suppressor, highlighting its context-dependent role. We here discuss differences and analogies of PBX1 roles during embryonic development and in cancer, focusing mainly on the most recent discoveries.

Correlation analysis of PBX family with immune invasion and drug sensitivity in colon adenocarcinoma

Objedtive

Pre-B cell leukemia (PBX) has been found to be associated with cancer, but poorly studied with colon adenocarcinoma (COAD). In this study, the correlation between PBX family and COAD pathogenesis and immune cytokine infiltration was further explored by analyzing online tumor databases, in order to find new biomarkers for the diagnosis of COAD.

Methods

The online database was used to analyze gene differential expression, methylation level, gene mutation rate, immune infiltration difference, drug sensitivity, and so on.

Results

PBX1 and PBX3 decreased in COAD. PBX2 and PBX4 increased. The expression of PBX1 and PBX2 in different clinical stages was different. PBX4 was valuable for the prognosis of COAD. PBX family has correlation between COAD and immune infiltration. PBX2 was correlated with different pathological stages. PBX3 had the highest gene mutation rate, followed by PBX1, PBX2 and PBX4. PBX1, PBX2 and PBX4 were correlated with the sensitivity of multiple drugs.

Conclusion

The PBX family is differentially expressed in COAD and has a genetic mutation, and its protein network is closely related to the HOX family and is associated with immune infiltration of COAD.

Single-cell multiomic analysis identifies a HOX-PBX gene network regulating the survival of lymphangioleiomyomatosis cells

Lymphangioleiomyomatosis (LAM) is a rare, progressive lung disease that predominantly affects women. LAM cells carry TSC1/TSC2 mutations, causing mTORC1 hyperactivation and uncontrolled cell growth. mTORC1 inhibitors stabilize lung function; however, sustained efficacy requires long-term administration, and some patients fail to tolerate or respond to therapy. Although the genetic basis of LAM is known, mechanisms underlying LAM pathogenesis remain elusive. We integrated single-cell RNA sequencing and single-nuclei ATAC-seq of LAM lungs to construct a gene regulatory network controlling the transcriptional program of LAM cells. We identified activation of uterine-specific HOX-PBX transcriptional programs in pulmonary LAMCORE cells as regulators of cell survival depending upon HOXD11-PBX1 dimerization. Accordingly, blockage of HOXD11-PBX1 dimerization by HXR9 suppressed LAM cell survival in vitro and in vivo. PBX1 regulated STAT1/3, increased the expression of antiapoptotic genes, and promoted LAM cell survival in vitro. The HOX-PBX gene network provides promising targets for treatment of LAM/TSC mTORC1-hyperactive cancers.

HOXA1, a breast cancer oncogene

More than 25 years ago, the first literature records mentioned HOXA1 expression in human breast cancer. A few years later, HOXA1 was confirmed as a proper oncogene in mammary tissue. In the following two decades, molecular data about the mode of action of the HOXA1 protein, the factors contributing to activate and maintain HOXA1 gene expression and the identity of its target genes have accumulated and provide a wider view on the association of this transcription factor to breast oncogenesis. Large-scale transcriptomic data gathered from wide cohorts of patients further allowed refining the relationship between breast cancer type and HOXA1 expression. Several recent reports have reviewed the connection between cancer hallmarks and the biology of HOX genes in general. Here we take HOXA1 as a paradigm and propose an extensive overview of the molecular data centered on this oncoprotein, from what its expression modulators, to the interactors contributing to its oncogenic activities, and to the pathways and genes it controls. The data converge to an intricate picture that answers questions on the multi-modality of its oncogene activities, point towards better understanding of breast cancer aetiology and thereby provides an appraisal for treatment opportunities.

Downstream of the HOX genes: explaining conflicting tumour suppressor and oncogenic functions in cancer

The HOX genes are a highly conserved group of transcription factors that have key roles in early development, but which are also highly expressed in most cancers. Many studies have found strong associative relationships between the expression of individual HOX genes in tumours and clinical parameters including survival. For the majority of HOX genes, high tumour expression levels seem to be associated with a worse outcome for patients, and in some cases this has been shown to result from the activation of pro-oncogenic genes and pathways. However, there are also many studies that indicate a tumour suppressor role for some HOX genes, sometimes with conclusions that contradict earlier work. In this review, we have attempted to clarify the role of HOX genes in cancer by focusing on their downstream targets as identified in studies that provide experimental evidence for their activation or repression. On this basis, the majority of HOX genes would appear to have a pro-oncogenic function, with the notable exception of HOXD10, which acts exclusively as a tumour suppressor. HOX proteins regulate a wide range of target genes involved in metastasis, cell death, proliferation, and angiogenesis, and activate key cell signalling pathways. Furthermore, for some functionally related targets, this regulation is achieved by a relatively small subgroup of HOX genes.

MicroRNA-141-3p inhibits the progression of oral squamous cell carcinoma via targeting PBX1 through the JAK2/STAT3 pathway

Oral squamous cell carcinoma (OSCC), which is the most common epithelial malignant neoplasm in the head and neck, is characterized by local infiltration and metastasis of lymph nodes. The five-year survival rate of OSCC remains low despite the advances in clinical methods. miR-141-3p has been shown to activate or inhibit tumorigenesis. However, the effects of miR-141-3p on invasion and migration of OSCC remain unclear. The present study aimed to evaluate the effects of miR-141-3p on invasion, proliferation, and migration in oral squamous cell carcinoma (OSCC). Reverse transcription quantitative PCR, western blotting and immunohistochemistry were used to detect microRNA(miR)-141-3p and pre-B-cell leukaemia homeobox-1 (PBX1) expression in OSCC tissues and cell lines. The luciferase reporter assay was used to detect targets of miR-141-3p in OSCC. MTT, Transwell and wound healing assays were used to determine the cell proliferation and invasive and migratory abilities, respectively. Expression of constitutive phosphorylated (p)-Janus kinase 2 (JAK2) and p-signal transducer and activator of transcription 3 (STAT3) was detected using western blotting in tissues and cells. miR-141-3p expression was decreased in OSCC tissues and cells, while PBX1 protein expression was increased compared with non-cancerous controls. The result from the dual-luciferase reporter assay revealed that PBX1 was the direct target of miR-141-3p in OSCC tissues. Furthermore, miR-141-3p overexpression and PBX1 knockdown could reduce cell invasion, proliferation and migration, and inhibit the JAK2/STAT3 pathway; however, miR-141-3p downregulation had the opposite effects. In addition, silencing of PBX1 using small interfering RNA could weaken the effects of miR-141-3p inhibitor on JAK2/STAT3 pathway and cell progression in CAL27 cells. In summary, the findings from this study indicated that miR-141-3p upregulation could inhibit OSCC cell invasion, proliferation and migration, by targeting PBX1 via the JAK2/STAT3 pathway.

PBX1-directed stem cell transcriptional program drives tumor progression in myeloproliferative neoplasm

PBX1 regulates the balance between self-renewal and differentiation of hematopoietic stem cells and maintains proto-oncogenic transcriptional pathways in early progenitors. Its increased expression was found in myeloproliferative neoplasm (MPN) patients bearing the JAK2V617F mutation. To investigate if PBX1 contributes to MPN, and to explore its potential as therapeutic target, we generated the JP mouse strain, in which the human JAK2 mutation is induced in the absence of PBX1. Typical MPN features, such as thrombocythemia and granulocytosis, did not develop without PBX1, while erythrocytosis, initially displayed by JP mice, gradually resolved over time; splenic myeloid metaplasia and in vitro cytokine independent growth were absent upon PBX1 inactivation. The aberrant transcriptome in stem/progenitor cells from the MPN model was reverted by the absence of PBX1, demonstrating that PBX1 controls part of the molecular pathways deregulated by the JAK2V617F mutation. Modulation of the PBX1-driven transcriptional program might represent a novel therapeutic approach.

Coexpression of HOXA6 and PBX2 promotes metastasis in gastric cancer

HOXA6 gene plays a role of the oncogene in various cancers. Nonetheless, its effect on gastric cancer (GC) occurrence and development is still unclear. We analysed whether HOXA6 interacts with the PBX2 protein using the STRING database. The molecular mechanism by which HOXA6 synergizes with PBX2 in GC metastasis is not fully understood. Here, we found that the expression of HOXA6 was increased in GC tissues and cell lines. The upregulation of HOXA6 was closely associated with differentiation, lymph node metastasis, AJCC stage, TNM stage, and poor survival outcome in GC patients based on tissue microarray (TMA) data. Moreover, the overexpression of HOXA6 promoted, whereas siRNA-mediated repression of HOXA6 inhibited, the cell proliferation, migration, and invasion of GC cells. Furthermore, HOXA6 could physically interact with and stabilize PBX2. In addition, HOXA6 and PBX2 expression was positively correlated in GC cells and tissue. HOXA6 and PBX2 suppression in GC cells also led to decreased migration and invasion potential in vitro. In vivo, HOXA6 was shown to cooperate with PBX2 to enhance cell metastasis via orthotopic implantation. These data indicate that HOXA6 promotes cell proliferation, migration, and invasion and that the HOXA6-PBX2 axis may be a useful biomarker for disease progression in GC.

Oncogenic and tumor suppressor function of MEIS and associated factors

MEIS proteins are historically associated with tumorigenesis, metastasis, and invasion in cancer. MEIS and associated PBX-HOX proteins may act as tumor suppressors or oncogenes in different cellular settings. Their expressions tend to be misregulated in various cancers. Bioinformatic analyses have suggested their upregulation in leukemia/lymphoma, thymoma, pancreas, glioma, and glioblastoma, and downregulation in cervical, uterine, rectum, and colon cancers. However, every cancer type includes, at least, a subtype with high MEIS expression. In addition, studies have highlighted that MEIS proteins and associated factors may function as diagnostic or therapeutic biomarkers for various diseases. Herein, MEIS proteins and associated factors in tumorigenesis are discussed with recent discoveries in addition to how they could be modulated by noncoding RNAs or newly developed small-molecule MEIS inhibitors.

Context-dependent HOX transcription factor function in health and disease

During animal development, HOX transcription factors determine the fate of developing tissues to generate diverse organs and appendages. The power of these proteins is striking: mis-expressing a HOX protein causes homeotic transformation of one body part into another. During development, HOX proteins interpret their cellular context through protein interactions, alternative splicing, and post-translational modifications to regulate cell proliferation, cell death, cell migration, cell differentiation, and angiogenesis. Although mutation and/or mis-expression of HOX proteins during development can be lethal, changes in HOX proteins that do not pattern vital organs can result in survivable malformations. In adults, mutation and/or mis-expression of HOX proteins disrupts their gene regulatory networks, deregulating cell behaviors and leading to arthritis and cancer. On the molecular level, HOX proteins are composed of DNA binding homeodomain, and large regions of unstructured, or intrinsically disordered, protein sequence. The primary roles of HOX proteins in arthritis and cancer suggest that mutations associated with these diseases in both the structured and disordered regions of HOX proteins can have substantial functional effects. These insights lead to new questions critical for understanding and manipulating HOX function in physiological and pathological conditions.

HOX genes as transcriptional and epigenetic regulators during tumorigenesis and their value as therapeutic targets

Several HOX genes are aberrantly expressed in a wide range of cancers interfering with their development and resistance to treatment. This seems to be often caused by alterations in the methylation profiles of their promoters. The role of HOX gene products in cancer is highly 'tissue specific', relying ultimately on their ability to regulate oncogenes or tumor-suppressor genes, directly as transcriptional regulators or indirectly interfering with the levels of epigenetic regulators. Nowadays, different strategies have been tested the use of HOX genes as therapeutic targets for cancer diagnosis and treatment. Here, we trace the history of the research concerning the involvement of HOX genes in cancer, their connection with epigenetic regulation and their potential use as therapeutic targets.

Direct and Indirect Targeting of HOXA9 Transcription Factor in Acute Myeloid Leukemia

HOXA9 (Homeobox A9) is a homeotic transcription factor known for more than two decades to be associated with leukemia. The expression of HOXA9 homeoprotein is associated with anterior-posterior patterning during embryonic development, and its expression is then abolished in most adult cells, with the exception of hematopoietic progenitor cells. The oncogenic function of HOXA9 was first assessed in human acute myeloid leukemia (AML), particularly in the mixed-phenotype associated lineage leukemia (MPAL) subtype. HOXA9 expression in AML is associated with aggressiveness and a poor prognosis. Since then, HOXA9 has been involved in other hematopoietic malignancies and an increasing number of solid tumors. Despite this, HOXA9 was for a long time not targeted to treat cancer, mainly since, as a transcription factor, it belongs to a class of protein long considered to be an "undruggable" target; however, things have now evolved. The aim of the present review is to focus on the different aspects of HOXA9 targeting that could be achieved through multiple ways: (1) indirectly, through the inhibition of its expression, a strategy acting principally at the epigenetic level; or (2) directly, through the inhibition of its transcription factor function by acting at either the protein/protein interaction or the protein/DNA interaction interfaces.