Aurora-A/SOX8/FOXK1 signaling axis promotes chemoresistance via suppression of cell senescence and induction of glucose metabolism in ovarian cancer organoids and cells

Rationale: Cisplatin derivatives are first-line chemotherapeutic agents for epithelial ovarian cancer. However, chemoresistance remains a major hurdle for successful therapy and the underlying molecular mechanisms are poorly understood at present.

Methods: RNA sequencing of organoids (PDO) established from cisplatin-sensitive and -resistant ovarian cancer tissue samples was performed. Glucose metabolism, cell senescence, and chemosensitivity properties were subsequently examined. Immunoprecipitation, mass spectrometry, Fӧrster resonance energy transfer-fluorescence lifetime imaging (FRET-FLIM), luciferase reporter assay, ChIP and animal experiments were conducted to gain insights into the specific functions and mechanisms of action of the serine/threonine kinase, Aurora-A, in ovarian cancer.

Results: Aurora-A levels were significantly enhanced in cisplatin-resistant PDO. Furthermore, Aurora-A promoted chemoresistance through suppression of cell senescence and induction of glucose metabolism in ovarian cancer organoids and cells. Mechanistically, Aurora-A bound directly to the transcription factor sex determining region Y-box 8 (SOX8) and phosphorylated the Ser327 site, in turn, regulating genes related to cell senescence and glycolysis, including hTERT, P16, LDHA and HK2, through enhancement of forkhead-box k1 (FOXK1) expression.

Conclusions: Aurora-A regulates cell senescence and glucose metabolism to induce cisplatin resistance by participating in the SOX8/FOXK1 signaling axis in ovarian cancer. Our collective findings highlight a novel mechanism of cisplatin resistance and present potential therapeutic targets to overcome chemoresistance in ovarian cancer.

SOX8 regulates permeability of the blood-testes barrier that affects adult male fertility in the mouse

Sertoli cells provide nutritional and physical support to germ cells during spermatogenesis. Sox8 encodes a member of the high mobility group of transcription factors closely related to Sox9 and Sox10. Sertoli cells express SOX8 protein, and its elimination results in an age-dependent dysregulation of spermatogenesis, causing adult male infertility. Among the claudin genes with altered expression in the Sox8(-/-) testes, was claudin-3, which is required for the regulation and maintenance of the blood-testes barrier (BTB). Because the BTB is critical in restricting small molecules in the luminal compartment of the seminiferous tubules, the aim of this study was to analyze the level of tight junction proteins (claudin-3, claudin-11, and occludin) and BTB permeability in Sox8(-/-) adult testes. The acetylation level of alpha-tubulin and microtubule organization was also evaluated because microtubules are critical in maintaining the microenvironment of the seminiferous epithelium. Western blot analysis shows that claudin-3 protein is decreased in Sox8(-/-) testes. Chromatin immunoprecipitation confirmed that SOX8 binds at the promoter region of claudin-3. Claudin-3 was localized to the Sertoli cell tight junctions of wild-type testes and significantly decreased in the Sox8(-/-) testes. The use of biotin tracers showed increased BTB permeability in the Sox8(-/-) adult testes. Electron microscopy analysis showed that microtubule structures were destabilized in the Sox8(-/-) testes. These results suggest that Sox8 is essential in Sertoli cells for germ cell differentiation, partly by controlling the microenvironment of the seminiferous epithelium.

Brief report: importance of SOX8 for in vitro chondrogenic differentiation of human mesenchymal stromal cells

The transcription factor SOX9 is believed to be the master regulator of chondrogenesis. SOX8 is another SOX group E transcription factor with a high degree of homology to SOX9. Here, we demonstrate that SOX8 mRNA levels decrease during in vitro dedifferentiation of human articular chondrocytes and increase during chondrogenic differentiation of mesenchymal stromal cells. Knockdown of SOX9 reduced the expression of SOX8, COL2A1, and a range of other chondrogenic molecules. SOX8 knockdown reduced the expression of a large number of overlapping chondrogenic molecules, but not SOX9. Neither siSOX9 nor siSOX8 altered expression of the hypertrophic marker gene COL10A1. siSOX9, but not siSOX8 led to upregulation of hypertrophy associated genes MMP13 and ALPL. Transfection of synthetic SOX5, 6, and 9 mRNA trio upregulated SOX8, COL2A1, and ACAN, but not COL10A1 mRNA. Replacement of synthetic SOX9 by SOX8 in the SOX trio showed similar but lower chondrogenic effect. We conclude that SOX8 expression is regulated by SOX9, and that both together with SOX5 and SOX6 are required as a SOX quartet for transcription of COL2A1 and a large number of other chondrogenic molecules. Neither SOX8 nor SOX9 affect COL10A1 expression, but SOX9 inhibits chondrocyte hypertrophy through inhibition of MMP13 and ALPL expression.

High SOX8 expression promotes tumor growth and predicts poor prognosis through GOLPH3 signaling in tongue squamous cell carcinoma

According to our previous study, GOLPH3 is markedly up-expressed in tongue squamous cell carcinoma (TSCC), which is also associated with poor survival. However, it remains unclear about key upstream and downstream mechanisms of GOLPH3. This study aimed to illuminate new mechanisms modulating GOLPH3 upregulation and promoting TSCC development at the molecular level. Using mass spectrometry and agarose-streptavidin-biotin pull-down analyses, SOX8 (SRY-Box 8) was identified to be the new protein to bind the GOLPH3 promoter within TSCC cells, which was further verified to be the regulator of GOLPH3 upregulation. The knockdown of SOX8 suppressed the promoter activity of GOLPH3, while secondarily inhibiting TSCC cell proliferation both in vivo and in vitro. Interestingly, GOLPH3 overexpression rescued the SOX8 knockdown-mediated suppression on TSCC proliferation. Additionally, exogenous over-expression of SOX8 also activated the activity of promoter as well as GOLPH3 expression, in the meantime of promoting TSCC development. Moreover it was discovered that SOX8 regulated GOLPH3 expression through interacting with TFAP2A. Moreover our results suggested that the SOX8 level was increased within tumor tissue compared with that in para-cancer normal counterpart, which showed positive correlation with the GOLPH3 level. According to Kaplan-Meier analyses, TSCC cases having higher SOX8 and GOLPH3 expression were associated with poorer prognostic outcomes. Taken together, this study reveals that SOX8 enhances the TSCC cell growth via the direct transcriptional activation of GOLPH3, which also indicates the potential to use SOX8/GOLPH3 pathway as the treatment target among TSCC patients.

Transcriptomic analysis of overexpressed SOX4 and SOX8 in TM4 Sertoli cells with emphasis on cell-to-cell interactions

Sertoli cells are localized in seminiferous tubules within the testis. They are the first testicular cells to differentiate during male sex determination. In the adult, Sertoli cells provide nutrients to germ cells, control factors for spermatogenesis and protection by establishing the blood-testis barrier (BTB). This BTB is composed of tight junctions, basal ectoplasmic specializations, adherent junctions and gap junctions. The transcription factor SOX8 is necessary for the maintenance of spermatogenesis during adult life whereas SOX4 is involved in developmental processes. These factors are highly expressed in Sertoli cells. However, few of their target genes in adult Sertoli cells are known. Hence, we compared the transcriptomes of TM4 Sertoli cells overexpressing or not SOX4 or SOX8 using RNA-Seq followed by pathways and networks analyses. We found that SOX4 overexpression leads to downregulated genes enriched for cell junction organization and positive regulation of cell-to-cell adhesion. Upregulated genes in response to SOX8 overexpression were enriched for Sertoli cell development and differentiation. However, downregulated genes were enriched for cell-to-cell adhesion, tight junction interactions, gap junctions' assembly, as well as extracellular matrix binding. Hence, our results confirm that SOX8 is an important mediator of Sertoli cell maturation, whereas SOX4 and SOX8 influence gene expression related to regulation of blood-testis barrier assembly. In addition, TM4 cells can be considered as a useful model to better define the regulatory mechanisms of SOX4 or SOX8 on gene transcription in Sertoli cells.

Two Different Copy Number Variations of the SOX5 and SOX8 Genes in Yak and Their Association with Growth Traits

Copy number variation (CNV) is a structural variant with significant impact on genetic diversity. CNV has been widely used in breeding for growth traits, meat production or quality, and coat color. SRY-like box genes (SOXs) are a class of transcription factors that play a regulatory role in cell fate specification and differentiation. SOX5 and SOX8 belong to subgroups D and E of the SOXs, respectively. Previous studies have shown that SOX5 and SOX8 are essential in the development of bones. In this study, we explored the association between the growth traits and CNVs of SOX5 and SOX8 in 326 Ashidan yaks and detected mRNA expression levels in different tissues. Our results illustrated that CNVs of SOX5 and SOX8 were significantly associated with withers height at 18 months of age and chest girth at 30 months of age (p < 0.05). The CNV combination of SOX5 and SOX8 was significantly associated with withers height at 18 months of age (p < 0.01). SOX5 expression in the lung was significantly higher than in the heart, spleen, kidney, and muscle (p < 0.05). SOX8 expression in the lung was significantly higher than in the liver and muscle (p < 0.05). Our results provide evidence that the CNVs of SOX5 and SOX8 genes could be used as new markers for the selection of yak growth traits.

Quantitative Proteomic Profiling Identifies SOX8 as Novel Regulator of Drug Resistance in Gestational Trophoblastic Neoplasia

The development of drug resistance remains one of the major challenges to current chemotherapeutic regimens in gestational trophoblastic neoplasia (GTN). Further understanding on the mechanisms of drug resistance would help to develop more effective therapy to treat GTN. Herein, tandem mass tag-based (TMT) quantitative proteomic technique was used to establish drug resistance-related proteomic profiles in chemoresistant GTN cell models (JEG3/MTX, JEG3/VP16, JEG3/5-Fu). In total, we identified 5,704 protein groups, among which 4,997 proteins were quantified in JEG3 and its chemoresistant sublines. Bioinformatics analysis revealed that multiple biological processes/molecular pathways/signaling networks were involved in the regulation of drug resistance in chemoresistant JEG3 sublines. SOX8 was upregulated in all the three chemoresistant sublines, and its function was further investigated. Knockdown of SOX8 significantly reduced cell viability, impaired soft agar clonogenesis, and increased caspase-3 activities after drug treatment in JEG3 chemoresistant sublines. In addition, over-expression of SOX8 promoted cell survival, enhanced soft agar clonogenesis, and attenuated caspase-3 activities after drug treatment in GTN cells. Importantly, SOX8 might be a potential regulator of reactive oxygen species (ROS) homeostasis, as SOX8 regulated the expression of antioxidant enzymes (GPX1, HMOX1) and reduced drug-induced ROS accumulation in GTN cell models. Collectively, SOX8 might promote drug resistance through attenuating the accumulation of ROS induced by chemotherapeutic drugs in GTN cells. Targeting SOX8 might be useful to sensitize GTN cells to chemotherapy.

SOX8 promotes cetuximab resistance via HGF/MET bypass pathway activation in colorectal cancer

AIM

Cetuximab is an essential drug for the treatment of wild-type K-RAS colorectal cancer (CRC). It improves the overall survival of patients. However, acquired resistance prevents its clinical efficacy. Tumor heterogeneity may be a nonnegligible reason for cetuximab resistance. We attempted to explore the corresponding molecular mechanism.

METHODS

Cetuximab-resistant CRC cell RKO and cetuximab-sensitive CRC cell Caco-2 were applied in this study. Cells were centrifuged to determine the concentration in the culture supernatant (CS). MTT, EdU, and colony formation assays were utilized to evaluate cell survival and proliferation. Chromatin immunoprecipitation (ChIP) and promoter-luciferase reporter assays were employed to confirm the direct binding of transcription factors. Western blot and reverse transcription-polymerase chain reaction (RT-PCR) assays were used to detect the expression of molecular markers in the pathway.

RESULTS

Hepatocyte growth factor (HGF) was up-regulated in RKO cell culture supernatant and induced cetuximab resistance in Caco-2 cells. SRY-Box Transcription Factor 8 (SOX8) bound to the promoter sequence of HGF. HGF activated the HGF/MET bypass pathway and induced cetuximab resistance in Caco-2 cells.

CONCLUSION

The SOX8/HGF/MET axis played a crucial role in the communication between cetuximab-resistant cells and cetuximab-sensitive cells, inducing treatment resistance.

Variation analysis of SOX8 gene in Chinese men with non-obstructive azoospermia or oligozoospermia

Sox8, encoding a SRY-related HMG box transcription factor, is essential in Sertoli cells for germ cell differentiation via regulation of integrity of the blood-testis barrier (BTB) as well as Sertoli-germ cell adhesion. Inactivation of Sox8 gene in mice causes postnatal progressive spermatogenic failure, resulting in male infertility. This study aims to investigate whether variants of SOX8 contribute to pathogenesis of idiopathic non-obstructive azoospermia (NOA) or oligozoospermia. A case-control genetic study was conducted in which all exons and exon-intron boundaries of SOX8 gene were screened in 190 NOA and 139 oligozoospermia cases by Sanger sequencing. The detected variants were examined in 284 normospermic controls. Nine known single-nucleotide polymorphisms (SNPs) of SOX8 gene were identified, and four of them exist simultaneously in oligo/azoospermia patients. A comparison of allele/genotype frequencies of these variants showed no significant difference between oligo/azoospermia cases and controls. The results indicate that deleterious variants in SOX8 gene may not be a common cause for oligo/azoospermia in Chinese men. Considering ethnic diversity, SOX8 could not be ruled out as a candidate gene for male infertility. The role of SOX8-mediated Sertoli cell function and BTB integrity played in the pathogenesis of male infertility needs to be further explored in other populations.

Whole-Exome Sequencing Identifies Genetic Variants for Severe Adolescent Idiopathic Scoliosis in a Taiwanese Population

Adolescent idiopathic scoliosis (AIS) is a three-dimensional spinal curvature deformity that appears in the adolescent period. In this study, we performed whole-exome sequencing on 11 unrelated Taiwanese patients with a Cobb's angle greater than 40 degrees. Our results identified more than 200 potential pathogenic rare variants, however, most of which were carried only by one individual. By in silico pathogenicity annotation studies, we found that TTN, CLCN1, and SOX8 were the most important genes, as multiple pathogenic variants were within these genes. Furthermore, biological functional annotation indicated critical roles of these AIS candidate genes in the skeletal muscle. Importantly, a pathogenic variant on SOX8 was shared by over 35% of the patients. These results highlighted TTN, CLCN1, and SOX8 as the most likely susceptibility genes for severe AIS.

SOX8 is essential for male sexual differentiation in the Chinese soft-shelled turtle Pelodiscus sinensis

SOX8, which belongs to SOXE transcription factor subfamily together with SOX9, participates in sex differentiation and testicular development by enhancing the function of SOX9 in mammals. However, the functional role of SOX8 in sex differentiation has not yet been identified in any non-mammalian vertebrates. Here, we found in the Chinese soft-shelled turtle Pelodiscus sinensis that SOX8 exhibited male-specific higher expression from stage 14 to 18, the critical period of sex determination, prior to the onset of gonadal differentiation. In addition, SOX8 was rapidly down-regulated during male-to-female sex reversal induced by estradiol. Moreover, knockdown of SOX8 led to complete feminization of ZZ P. sinensis, determined by gonadal morphology and distribution of germ cells, as well as the down-regulation of testicular marker DMRT1 and the up-regulation of ovarian regulator FOXL2. In conclusion, this study provides evidence that SOX8 is a key regulator of early male differentiation in P. sinensis, highlighting the significance of the SOX family in reptile sex determination.

Notoginsenoside R2 reduces Aβ25-35-induced neuronal apoptosis and inflammation via miR-27a/SOX8/β-catenin axis

Background: Alzheimer's disease (AD) has affected numerous elderly individuals worldwide. Panax notoginseng has been shown to ameliorate AD symptoms, and notoginsenoside R2 is a key saponin identified in this plant. Purpose: In the current study, we aimed to explore whether notoginsenoside R2 could improve the prognosis of AD. Methods: Herein, primary rat cortical neurons were isolated and they were treated with amyloid beta-peptide (Aβ) 25-35 oligomers. Cellular apoptosis was examined via flow cytometry and Western blotting. miR-27a and SOX8 mRNA expression levels were quantified by quantitative reverse transcription-polymerase chain reaction. Furthermore, the interaction between miR-27a and SOX8 was investigated by utilizing a dual-luciferase reporter assay. Finally, an AD mouse model was established to validate the in vitro findings. Results: Notoginsenoside R2 alleviated Aβ25-35-triggered neuronal apoptosis and inflammation. During this process, miR-27a expression was decreased by notoginsenoside R2, and miR-27a negatively modulated SOX8 expression. Furthermore, activation of SOX8 upregulated β-catenin expression, thus suppressing apoptosis and neuroinflammation. Conclusions: Our animal experiments revealed that notoginsenoside R2 enhanced the cognitive function of AD mice and inhibited neuronal apoptosis. Notoginsenoside R2 ameliorated AD symptoms by reducing neuronal apoptosis and inflammation, thus suggesting a novel direction for AD pharmacotherapy.

The oncogenic role of SOX8 in endometrial carcinoma

Endometrial carcinoma (EC) remains one of the most prevalent forms of cancer to impact the female reproductive system, yet the mechanisms governing its development and progression are incompletely understood. We, therefore, sought to assess the relevance of SOX8 to EC progression and patient prognosis. Array comparative genomic hybridization (aCGH) was performed using samples from 50 patients with EC. Samples were separated based upon whether patients were positive for lymph node metastasis (LN+ and LN-, respectively). Based on our initial results, the SOX8 gene was selected for further analysis. Immunohistochemical staining of 630 endometrial tissue samples was conducted to understand how SOX8 expression relates to specific EC clinicopathological characteristics. In addition, we explored the impact of SOX8 expression on the growth, invasion, and migration of EC cells through knockdown and overexpression experiments. In our initial aCGH analysis, SOX family proteins and the Wnt and Notch signaling pathways were significantly associated with EC LN metastasis. SOX8 expression was markedly increased in EC tumor samples relative to normal endometrial tissue (P= .003), and higher SOX8 expression was linked to a high tumor histological grade (P= .032), LN metastasis (P= .027), and shorter patient overall survival (P= .031). When SOX8 was knocked down, this further impaired the proliferative, invasive, and migratory activity of EC cells, whereas overexpressing this gene had the opposite effect. SOX8 may function in an oncogenic manner to drive EC development and progression, and higher SOX8 expression is associated with a poor EC patient prognosis.

SRY-Related Transcription Factors in Head and Neck Squamous Cell Carcinomas: In Silico Based Analysis

Head and neck squamous cell carcinoma (HNSCC) is the sixth leading cancer and the fifth cause of cancer-related deaths worldwide with a poor 5-year survival. SOX family genes play a role in the processes involved in cancer development such as epithelial-mesenchymal transition (EMT), the maintenance of cancer stem cells (CSCs) and the regulation of drug resistance. We analyzed the expression of SOX2-OT, SOX6, SOX8, SOX21, SOX30 and SRY genes in HNSCC patients using the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) datasets, to assess their biological role and their potential utility as biomarkers. We demonstrated statistically significant differences in expression between normal and primary tumor tissues for SOX6, SOX8, SOX21 and SOX30 genes and pointed to SOX6 as the one that met the independent diagnostic markers criteria. SOX21 or SRY alone, or the panel of six SRY-related genes, could be used to estimate patient survival. SRY-related genes are positively correlated with immunological processes, as well as with keratinization and formation of the cornified envelope, and negatively correlated with DNA repair and response to stress. Moreover, except SRY, all analyzed genes were associated with a different tumor composition and immunological profiles. Based on validation results, the expression of SOX30 is higher in HPV(+) patients and is associated with patients' survival. SRY-related transcription factors have vast importance in HNSCC biology. SOX30 seems to be a potential biomarker of HPV infection and could be used as a prognostic marker, but further research is required to fully understand the role of SOX family genes in HNSCC.

Excessive SOX8 reprograms energy and iron metabolism to prime hepatocellular carcinoma for ferroptosis

Lipid peroxidation and redox imbalance are hallmarks of ferroptosis, an iron-dependent form of cell death. Growing evidence suggests that dysregulation in glycolipid metabolism and iron homeostasis substantially contribute to the development of hepatocellular carcinoma (HCC). However, there is still a lack of comprehensive understanding regarding the specific transcription factors that are capable of coordinating glycolipid and redox homeostasis to initiate the onset of ferroptosis. We discovered that overexpression of SOX8 leads to impaired mitochondria integrate, increased oxidative stress, and enhanced lipid peroxidation. These effects can be attributed to the inhibitory impact of SOX8 on de novo lipogenesis, glycolysis, the tricarboxylic acid cycle (TCA), and the pentose phosphate pathway (PPP). Additionally, upregulation of SOX8 results in reduced synthesis of NADPH, disturbance of redox homeostasis, disruption of mitochondrial structure, and impairment of the electron transport chain. Furthermore, the overexpression of SOX8 enhances the process of ferroptosis by upregulating the expression of genes associated with ferroptosis and elevating intracellular levels of ferrous ion. Importantly, the overexpressing of SOX8 has been observed to inhibit the proliferation of HCC in immunodeficient animal models. In conclusion, the findings suggest that SOX8 has the ability to alter glycolipid and iron metabolism of HCC cells, hence triggering the process of ferroptosis. The results of our study present a novel strategy for targeting ferroptosis in the therapy of HCC.

SOX8 Affects Tumoral SPARC Expression by Regulating EZH2 to Attenuate Effectiveness of albumin-bound paclitaxel in PDAC

Pancreatic cancer is a dismal malignancy with poor prognosis. In spite of progress in surgical technology, chemotherapy is still the cornerstone in the multi-disciplinary treatment. Albumin-bound paclitaxel is a first-line treatment for PDAC patients. Yet the response rate of the drug is far from satisfying. SOX8 is a member of the sex determining region Y-boxes family, which is potentially related to the chemoresistance of tumor. Patient with high expression of SOX8 were insensitive to albumin-bound paclitaxel. SOX8 reduced apoptosis and G2/M cell cycle arrest caused by albumin-bound paclitaxel. SOX8 transcriptionally regulated EZH2, which reduced expression of SPARC by promoting the methylation of SPARC, thereby reducing the transport of albumin-bound paclitaxel in pancreatic cancer cells. EZH2 inhibitor, UNC1999, can reverse the effect of SOX8 on chemo-resistance of albumin-bound paclitaxel. Collectively, our data revealed SOX8/EZH2/SPARC signaling induced primary chemo-resistance of albumin-bound paclitaxel in pancreatic ductal adenocarcinoma.

SOX8 promotes tumor growth and metastasis through FZD6-dependent Wnt/β-catenin signaling in colorectal carcinoma

SOX8 plays an important role in several physiological processes. Its expression is negatively associated with overall survival in patients with colorectal carcinoma (CRC), suggesting SOX8 is a potential prognostic factor for this disease. However, the role of SOX8 in CRC remains largely unknown. In this study, our data showed that SOX8 expression was upregulated in CRC cell lines and tumor tissues. Stable knockdown of SOX8 in CRC cell lines dramatically reduced cell proliferation, migration, and invasion. Furthermore, the knockdown of SOX8 decreased the phospho-GSK3β level and suppressed Frizzled-6 (FZD6) transcription; restoration of FZD6 expression partially abolished the effect of SOX8 on Wnt/β-catenin signaling and promote CRC cell proliferation. In conclusion, our findings suggested that SOX8 served as an oncogene in CRC through the activation of FZD6-dependent Wnt/β-catenin signaling.