Expression profile of SIX family members correlates with clinic-pathological features and prognosis of breast cancer: A systematic review and meta-analysis

SIX1 expression and its clinicopathological significance: difference between classic and follicular variant papillary thyroid carcinoma

BACKGROUND

Papillary thyroid carcinoma (PTC) is the most common type of thyroid carcinoma, representing the majority of thyroid cancer cases. Most patients with PTC have an excellent prognosis following treatment, yet approximately 10% face mortality within ten years, primarily due to lymph node metastasis (LNM) or local recurrence. The SIX1 gene, a member of the SIX gene superfamily, encodes a transcription factor integral to the development of certain tissues during embryogenesis. The impact of SIX1 in different subtypes of PTC has not been studied previously.

OBJECTIVE

The purpose of this study was to investigate the expression of SIX1 protein in PTC and to explore its relationship with clinical behavior in two subtypes of PTC: classic PTC (C-PTC) and follicular variant PTC (FV-PTC).

MATERIALS AND METHODS

Using immunohistochemistry, the study analyzed 125 primary PTC cases, including 85 cases of C-PTC and 40 cases of FV-PTC.

RESULTS

The study found significant positive associations between high SIX1 expression and several adverse clinical features across the PTC samples. High SIX1 expression was linked with increased tumor size, multifocal tumors, LNM, high-grade tumor features, advanced tumor stage, lymphovascular invasion, perineural invasion, and extrathyroidal extension (ETE). Within the classic PTC subgroup, high SIX1 expression showed significant positive correlations with Tumor size (P = 0.04), Multifocality (P = 0.02) and High-grade features (P = 0.03). In the follicular variant subgroup, high SIX1 expression was significantly associated with Lymph node metastasis (LNM) (P = 0.001), Lymphovascular invasion (P = 0.03), ETE (P = 0.003) and tumor stage (P = 0.007).

CONCLUSIONS

The findings of this study indicate that SIX1 expression is a marker of poor prognosis in PTC, suggesting that its high expression is linked with more aggressive tumor characteristics and advanced disease stages. Importantly, the impact of SIX1 expression varies between C-PTC and FV-PTC, predicting distinct prognostic factors in each subtype. This suggests that SIX1 could be utilized not only as a prognostic biomarker but also in developing subtype-specific therapeutic strategies for PTC patients.

S100A8/A9 as a risk factor for breast cancer negatively regulated by DACH1

BACKGROUND

S100A8 and S100A9 are members of Ca2+-binding EF-hand superfamily, mainly expressed by macrophages and neutrophils. Limited by the poor stability of homodimers, they commonly exist as heterodimers. Beyond acting as antibacterial cytokines, S100A8/A9 is also associated with metabolic and autoimmune diseases such as obesity, diabetes, and rheumatoid arthritis. While the involvement of S100A8/A9 in breast cancer development has been documented, its prognostic significance and the precise regulatory mechanisms remain unclear.

METHODS

S100A8/A9 protein in breast cancer samples was evaluated by immunohistochemistry staining with tumor tissue microarrays. The serum S100A8 concentration in patients was measured by enzyme-linked immunosorbent assay (ELISA). The S100A8 secreted by breast cancer cells was detected by ELISA as well. Pooled analyses were conducted to explore the relationships between S100A8/A9 mRNA level and clinicopathological features of breast cancer patients. Besides, the effects of S100A8/A9 and DACH1 on patient outcomes were analyzed by tissue assays. Finally, xenograft tumor assays were adopted to validate the effects of DACH1 on tumor growth and S100A8/A9 expression.

RESULTS

The level of S100A8/A9 was higher in breast cancer, relative to normal tissue. Increased S100A8/A9 was related to poor differentiation grade, loss of hormone receptors, and Her2 positive. Moreover, elevated S100A8/A9 predicted a worse prognosis for breast cancer patients. Meanwhile, serum S100A8 concentration was upregulated in Grade 3, basal-like, and Her2-overexpressed subtypes. Additionally, the results of public databases showed S100A8/A9 mRNA level was negatively correlated to DACH1. Stable overexpressing DACH1 in breast cancer cells significantly decreased the generation of S100A8. The survival analysis demonstrated that patients with high S100A8/A9 and low DACH1 achieved the shortest overall survival. The xenograft models indicated that DACH1 expression significantly retarded tumor growth and downregulated S100A8/A9 protein abundance.

CONCLUSION

S100A8/A9 is remarkedly increased in basal-like and Her2-overexpressed subtypes, predicting poor prognosis of breast cancer patients. Tumor suppressor DACH1 inhibits S100A8/A9 expression. The combination of S100A8/A9 and DACH1 predicted the overall survival of breast cancer patients more preciously.

Combination of SIX4-siRNA and temozolomide inhibits the growth and migration of A-172 glioblastoma cancer cells

Glioblastoma is one of the most common and invasive types of primary brain malignancies in adults, accounting for 45.5% of malignancies. Its annual prevalence is low compared to other cancers. The survival rate of this disease is about 14 months after diagnosis. Temozolomide (TMZ) is a common chemotherapy drug used to treatment of glioblastoma, but drug resistance against this drug is an important barrier to successful treatment of this cancer. Today, siRNAs play a significant role in cancer treatment. SIX4 is a transcriptional regulatory molecule that can act as a transcriptional suppressor and an activator in target genes involved in differentiation, migration, and cell survival processes. The aim of this study was to evaluate the effect of SIX4-siRNA on A-172 glioblastoma cells, its role as a tumor suppressor, and its combination with TMZ. We studied the cytotoxic effect of the SIX4-siRNA and TMZ on A-172 cells using the MTT assay investigated their effect on apoptosis and cell cycle of A-172 cells used wound healing assays to assess their effect on cell migration. Finally, we used qRT-PCR to study the mRNA expression levels of genes involved in apoptosis and migration of tumoral cells after treatments. Based on our results, silencing SIX4-siRNA expression reduced the cell viability of A-172 cells and sensitize these cells to TMZ. Furthermore, we observed an increase in apoptosis and cell cycle arrest, and a decrease in migration. Bax and caspase-9 overexpression and BCL2 and MMP9 downregulation were detected in the combination of SIX4-siRNA and TMZ. According to our results, the combination of SIX4-siRNA and TMZ can be a very useful strategy for successful glioblastoma treatment.

Silencing of SiX-4 enhances the chemosensitivity of melanoma cells to Cisplatin

Melanoma is the riskiest type of skin cancer. Its prevalence has been rapidly increased over the last three decades. SIX1, SIX2, SIX3, SIX4, SIX5, and SIX6 are members of the sine oculis homeobox (SIX) homolog family. It is imperative to identify new melanoma biomarkers to improve the predictive value for melanoma prognosis, which could enhance our understanding of carcinogenesis and tumor progression. In this study, we investigated whether silencing of SIX4 in a melanoma cell line (A375 cells) in combination with Cisplatin can affect the apoptosis and suppression of cell cycle progression, migration of the melanoma cells. MTT test and colony formation assay was applied to determine the IC50 of Cisplatin and the combined effect of SIX4 siRNA and Cisplatin on the viability and clonogenesis of the A-375 cells. qRT-PCR was performed to determine the c-myc, BCL-2, BAX, MMP-9, CXCR4, and Rock genes expression. Furthermore, flow cytometry was applied to evaluate apoptosis, autophagy, and the cell cycle status in different groups. Finally, wound healing assay was employed to evaluate the effect of this combination therapy on migratory capacity. SIX4 suppression increased the chemosensitivity of A-375 cells to Cisplatin and decreased its efficient dose. Furthermore, SIX4 suppression alongside Cisplatin reduced cell migration rate, arrested the cell cycle at the G1 phase, induced apoptosis by modulating the expression of apoptotic target genes, induced autophagy, and also significantly inhibits clonogenesis of A-375 cells. SIX4 plays a significant role in the chemosensitivity and pathogenesis of melanoma. Therefore, SIX4 suppression, in combination with Cisplatin, may be a promising therapeutic approach in treating melanoma.

SIX3 function in cancer: progression and comprehensive analysis

The homeobox gene family encodes transcription factors that are essential for cell growth, proliferation, and differentiation, and its dysfunction is linked to tumor initiation and progression. Sine oculis homeobox (SIX) belongs to the homeobox gene family, with SIX3 being a core member. Recent studies indicate that SXI3 functions as a cancer suppressor or promoter, which is mainly dependent on SIX3's influence on the signal pathways that promote or inhibit cancer in cells. The low expression of SIX3 in most malignant tumors was confirmed by detailed studies, which could promote the cell cycle, proliferation, migration, and angiogenesis. The recovery or upregulation of SIX3 expression to suppress cancer is closely related to the direct or indirect inhibition of the Wnt pathway. However, in some malignancies, such as esophageal cancer and gastric cancer, SIX3 is a tumor-promoting factor, and repressing SIX3 improves patients' prognosis. This review introduces the research progress of SIX3 in tumors and gives a comprehensive analysis, intending to explain why SIX3 plays different roles in different cancers and provide new cancer therapy strategies.

Ginsenoside Rh4 Suppresses Metastasis of Gastric Cancer via SIX1-Dependent TGF-β/Smad2/3 Signaling Pathway

Gastric cancer (GC) is the leading causes of cancer-related death worldwide. Surgery remains the cornerstone of gastric cancer treatment, and new strategies with adjuvant chemotherapy are currently gaining more and more acceptance. Ginsenoside Rh4 has excellent antitumor activity. Conversely, the mechanisms involved in treatment of GC are not completely understood. In this study, we certified that Rh4 showed strong anti-GC efficiency in vitro and in vivo. MTT and colony formation assays were performed to exhibit that Rh4 significantly inhibited cellular proliferation and colony formation. Results from the wound healing assay, transwell assays, and Western blotting indicated that Rh4 restrained GC cell migration and invasion by reversing epithelial–mesenchymal transition (EMT). Further validation by proteomic screening, co-treatment with disitertide, and SIX1 signal silencing revealed that SIX1, a target of Rh4, induced EMT by activating the TGF-β/Smad2/3 signaling pathway. In summary, our discoveries demonstrated the essential basis of the anti-GC metastatic effects of Rh4 via suppressing the SIX1–TGF-β/Smad2/3 signaling axis, which delivers a new idea for the clinical treatment of GC.

The Significance of SIX1 as a Prognostic Biomarker for Survival Outcome in Various Cancer Patients: A Systematic Review and Meta-Analysis

Sine Oculis Homeobox Homolog 1 (SIX1) is reported to promote cancer initiation and progression in many preclinical models and is demonstrated in human cancer tissues. However, the correlation between SIX1 and cancer patients’ prognosis has not yet been systematically evaluated. Therefore, we performed a systematic review and meta-analysis in various human cancer types and extracted some data from TCGA datasets for further verification and perfection. We constructed 27 studies and estimated the association between SIX1 expression in various cancer patients’ overall survival and verified with TCGA datasets. Twenty-seven studies with 4899 patients are include in the analysis of overall, and disease-free survival, most of them were retrospective. The pooled hazard ratios (HRs) for overall and disease-free survival in high SIX1 expression patients were 1.54 (95% CI: 1.32-1.80, P<0.00001) and 1.83 (95% CI: 1.31-2.55, P=0.0004) respectively. On subgroup analysis classified in cancer type, high SIX1 expression was associated with poor overall survival in patients with hepatocellular carcinoma (HR 1.50; 95% CI: 1.17-1.93, P =0.001), breast cancer (HR 1.31; 95% CI: 1.10-1.55, P =0.002) and esophageal squamous cell carcinoma (HR 1.89; 95% CI: 1.42-2.52, P<0.0001). Next, we utilized TCGA online datasets, and the consistent results were verified in various cancer types. SIX1 expression indicated its potential to serve as a cancer biomarker and deliver prognostic information in various cancer patients. More works still need to improve the understandings of SIX1 expression and prognosis in different cancer types.

The SIX Family of Transcription Factors: Common Themes Integrating Developmental and Cancer Biology

The sine oculis (SIX) family of transcription factors are key regulators of developmental processes during embryogenesis. Members of this family control gene expression to promote self-renewal of progenitor cell populations and govern mechanisms of cell differentiation. When the function of SIX genes becomes disrupted, distinct congenital defects develops both in animal models and humans. In addition to the embryonic setting, members of the SIX family have been found to be critical regulators of tumorigenesis, promoting cell proliferation, epithelial-to-mesenchymal transition, and metastasis. Research in both the fields of developmental biology and cancer research have provided an extensive understanding of SIX family transcription factor functions. Here we review recent progress in elucidating the role of SIX family genes in congenital disease as well as in the promotion of cancer. Common themes arise when comparing SIX transcription factor function during embryonic and cancer development. We highlight the complementary nature of these two fields and how knowledge in one area can open new aspects of experimentation in the other.

SIX1/EYA1 are novel liver damage biomarkers in chronic hepatitis B and other liver diseases

Background

This study aimed to investigate the clinicopathological significance of sine oculis homeobox homolog 1 (SIX1) and eyes absent 1 (EYA1) in patients with chronic hepatitis B (CHB) and other liver diseases.

Methods

SIX1 and EYA1 levels were detected in human serum and liver tissues by enzyme linked immunosorbent assay (ELISA) and immunofluorescent staining method, respectively.

Results

The serum SIX1 and EYA1 levels in 313 CHB patients were 7.24±0.11 and 25.21±0.51 ng/mL, respectively, and these values were significantly higher than those in 33 healthy controls (2.84±0.15 and 13.11±1.01 ng/mL, respectively; P<0.05). Serum SIX1 and EYA1 levels were also markedly increased in patients with numerous other liver diseases, including liver fibrosis, hepatocellular carcinoma, fatty liver disease, alcoholic liver disease, fulminant hepatic failure, autoimmune liver disease, and hepatitis C, compared to the healthy controls (P<0.05). Dynamic observation of these proteins over time in 35 selected CHB patients revealed that SIX1 and EYA1 serum levels increased over an interval. Immunofluorescent staining revealed that both SIX1 and EYA1 were only expressed in hepatic stellate cells (HSCs), and their increased expression was evident in CHB liver tissue.

Conclusions

SIX1 and EYA1 are novel biomarkers of liver damage in patients of CHB and other liver diseases, with potential clinical utility.

Silencing SIX1 inhibits epithelial mesenchymal transition through regulating TGF-β/Smad2/3 signaling pathway in papillary thyroid carcinoma

OBJECTIVE

To investigate the sineoculis homeobox homolog 1 (SIX1) affect the epithelial mesenchymal transition (EMT) in papillary thyroid carcinoma (PTC) through regulating TGF-β/Smad2/3 signaling pathway.

METHODS

The SIX1 expression in cytological specimens, tissues or PTC cell lines was detected by qRT-PCR, western blotting or immunohistochemistry. A series of vitro experiments including flow cytometry, CCK-8, wound-healing and Transwell were used to evaluate the biological characteristics in a PTC cell line (NPA cells), which were divided into Blank, Negative control (NC), SIX1, SIX1-siRNA, LY-364947 (TGF-β/Smad2/3 pathway inhibitor) and SIX1 + LY-364947 groups. TGF-β/Smad2/3 pathway and EMT related protein expression were measured by qRT-PCR and western blotting.

RESULTS

SIX1 mRNA expression was increased in cytological specimens from PTC patients as compared with the non-toxic nodular goitre (NTG) patients. Moreover, compared with adjacent normal tissues, expressions of SIX1, N-cadherin and Vimentin were higher while E-cadherin was lower in PTC tissues; and SIX1 was positively correlated with N-cadherin and Vimentin but was negatively correlated with E-cadherin. Furthermore, the SIX1 expression was associated with histopathology, extrathyroidal extension (ETE), lymph node metastasis (LNM), pT stage, TNM stage, and distant metastasis. In addition, the expressions of TGFβ1, p-SMAD2/3, N-cadherin and Vimentin were downregulated in NPA cells after LY-364947 treatment with upregulated E-cadherin, decreased cell proliferation and metastasis, and enhanced cell apoptosis, which was reversed by SIX1 overexpression.

CONCLUSION

Silencing SIX1 can inhibit TGF-β/Smad2/3 pathway, thereby suppressing EMT in PTC, which may be a novel avenue for the treatment of PTC.

SIX6 is a TAL1-regulated transcription factor in T-ALL and associated with inferior outcome

T-cell acute lymphoblastic leukemia (T-ALL) is a hematological malignancy driven by abnormal activity of transcription factors. Here we report an aberrant expression of the developmental transcription factor SIX6 in the TAL1-subtype of T-ALL. Our results demonstrate that the binding of TAL1 and GATA3 transcription factors into an upstream enhancer element directly regulates SIX6 expression. High expression of SIX6 was associated with inferior event-free survival within three independent patient cohorts. At a functional level, CRISPR-Cas9-mediated knockout of the SIX6 gene in TAL1 positive Jurkat cells induced changes in genes associated with the mTOR-, K-RAS-, and TNFα-related molecular signatures but did not impair cell proliferation or viability. There was also no acceleration of T-ALL development within a Myc driven zebrafish tumor model in vivo. Taken together, our results show that SIX6 belongs to the TAL1 regulatory gene network in T-ALL but is alone insufficient to influence the development or maintenance of T-ALL.

RDGN-based predictive model for the prognosis of breast cancer

Background

Breast cancer is the most diagnosed malignancy in females in the United States. The members of retinal determination gene network (RDGN) including DACH, EYA, as well as SIX families participate in the proliferation, apoptosis, and metastasis of multiple tumors including breast cancer. A comprehensive predictive model of RDGN might be helpful to herald the prognosis of breast cancer patients.

Methods

In this study, the Gene Expression Ominibus (GEO) and Gene Set Expression Analysis (GSEA) algorithm were used to investigate the effect of RDGN members on downstream signaling pathways. Besides, based on The Cancer Genome Atlas (TCGA) database, we explored the expression patterns of RDGN members in tumors, normal tissues, and different breast cancer subtypes. Moreover, we estimated the relationship between RDGN members and the outcomes of breast cancer patients. Lastly, we constructed a RDGN-based predictive model by Cox proportional hazard regression and verified the model in two separate GEO datasets.

Results

The results of GSEA showed that the expression of DACH1 was negatively correlated with cell cycle and DNA replication pathways. On the contrary, the levels of EYA2 and SIX1 were significantly positively correlated with DNA replication, mTOR, and Wnt pathways. Further investigation in TCGA database indicated that DACH1 expression was lower in breast cancers especially basal-like subtype. In the meanwhile, SIX1 was remarkably upregulated in breast cancers while EYA2 level was increased in Basal-like and Her-2 enriched subtypes. Survival analyses demonstrated that DACH1 was a favorable factor while EYA2 and SIX1 were risk factors for breast cancer patients. Given the results of Cox proportional hazard regression analysis, two members of RDGN were involved in the present predictive model and patients with high model index had poorer outcomes.

Conclusion

This study showed that aberrant RDGN expression was an unfavorable factor for breast cancer. This RDGN-based comprehensively framework was meaningful for predicting the prognosis of breast cancer patients.

A novel prognostic model based on multi-omics features predicts the prognosis of colon cancer patients

Background

As a common malignant tumor in the colon, colon cancer (CC) has high incidence and recurrence rates. This study is designed to build a prognostic model for CC.

Methods

The gene expression dataset, microRNA‐seq dataset, copy number variation (CNV) dataset, DNA methylation dataset, and transcription factor (TF) dataset of CC were downloaded from UCSC Xena database. Using limma package, the differentially methylated genes (DMGs), and differentially expressed genes (DEGs) and miRNAs (DEMs) were identified. Based on random forest method, prognostic model for each omics dataset were constructed. After the omics features related to prognosis were selected using logrank test, the prognostic model based on multi‐omics features was built. Finally, the clinical phenotypes correlated with prognosis were screened using Kaplan–Meier survival analysis, and the nomogram model was established.

Results

There were 1625 DEGs, 268 DEMs, and 386 DMGs between the tumor and normal samples. A total of 105, 29, 159, five, and six genes/sites significantly correlated with prognosis were identified in the gene expression dataset (GABRD), miRNA‐seq dataset (miR‐1271), CNV dataset (RN7SKP247), DNA methylation dataset (cg09170112 methylation site [located in SFSWAP]), and TF dataset (SIX5), respectively. The prognostic model based on multi‐omics features was more effective than those based on single omics dataset. The number of lymph nodes, pathologic_M stage, and pathologic_T stage were the clinical phenotypes correlated with prognosis, based on which the nomogram model was constructed.

Conclusion

The prognostic model based on multi‐omics features and the nomogram model might be valuable for the prognostic prediction of CC.

Upregulation of sine oculis homeobox homolog 3 is associated with proliferation, invasion, migration, as well as poor prognosis of esophageal cancer

Esophageal cancer (EC) is a common cancer worldwide. Sine oculis homeobox homolog (SIX3) is a human transcription factor that regulates the progression of vertebrate eye and fetal forebrain. However, studies on the function of SIX3 in human tumorigenesis remain rare. In this study, we aim to evaluate the role and the significance of SIX3 in EC. The TCGA database and clinical samples were used to assess the expression of SIX3 in EC patients. The Kaplan-Meier method and Cox's proportional hazards model were performed to analyze the correlations between SIX3 expression and EC clinical outcomes. The expressions of SIX3 in EC cells were measured by quantitative reverse transcription PCR analysis. The cell proliferation was detected using cell counting kit-8 and colony formation assay. The migration and invasion capacity of EC cells were evaluated using wound healing and Transwell methods. Western blot assay was used to measure the alterations in some important protein expression levels in the PI3K/Akt signaling pathway. We found that SIX3 was highly expressed in the EC tissues and cells. In addition, high expression of SIX3 was related to poor survival. The knockdown of SIX3 significantly inhibited the proliferation, migration, and invasion of ECA109 cells. A similar pattern was also found in the proliferation and migration of SKGT-4 cell line. The expression levels of some key proteins in the PI3K/Akt signaling pathway were obviously decreased after cells were transfected with si-SIX3, possibly resulting in PI3K/AKT signaling inactivation. In addition, E-cadherin and N-cadherin showed some change. Collectively, the results shed light on a potentially promoting role of SIX3 in human EC. Thus, SIX3 might be considered a novel prognostic biomarker and therapeutic target for EC patients.

Recent advances with cyclin-dependent kinase inhibitors: therapeutic agents for breast cancer and their role in immuno-oncology

Introduction: Collaborative interactions between several diverse biological processes govern the onset and progression of breast cancer. These processes include alterations in cellular metabolism, anti-tumor immune responses, DNA damage repair, proliferation, anti-apoptotic signals, autophagy, epithelial-mesenchymal transition, components of the non-coding genome or onco-mIRs, cancer stem cells and cellular invasiveness. The last two decades have revealed that each of these processes are also directly regulated by a component of the cell cycle apparatus, cyclin D1. Area covered: The current review is provided to update recent developments in the clinical application of cyclin/CDK inhibitors to breast cancer with a focus on the anti-tumor immune response. Expert opinion: The cyclin D1 gene encodes the regulatory subunit of a proline-directed serine-threonine kinase that phosphorylates several substrates. CDKs possess phosphorylation site selectivity, with the phosphate-acceptor residue preceding a proline. Several important proteins are substrates including all three retinoblastoma proteins, NRF1, GCN5, and FOXM1. Over 280 cyclin D3/CDK6 substrates have b\een identified. Given the diversity of substrates for cyclin/CDKs, and the altered thresholds for substrate phosphorylation that occurs during the cell cycle, it is exciting that small molecular inhibitors targeting cyclin D/CDK activity have encouraging results in specific tumors.

PPARG Negatively Modulates Six2 in Tumor Formation of Clear Cell Renal Cell Carcinoma

Substantial research has revealed that peroxisome proliferator-activated receptor-gamma (PPARG) plays a critical role in glucose homeostasis and lipid metabolism, and recent studies have shown different effects in the progression of different tumors. However, the role of PPARG and its target gene in clear cell renal cell carcinoma (ccRCC) are incompletely understood. Clinical data revealed abnormal glucolipid metabolism in primary ccRCC samples. In addition, transcriptional profiling indicated that PPARG expression was positively correlated, whereas Six2 expression was negatively correlated with the overall survival of ccRCC patients. Staining showed that PPARG was mainly expressed in tumor cell cytoplasm, and Six2 was localized to the nuclei. In a ccRCC cell line, PPARG activation promoted cell apoptosis, inhibited cell migration and proliferation, and reduced Six2 expression. Mechanistically, overexpressing Six2 downregulated E-cadherin expression and cell apoptosis, but PPARG activation reversed those effects. Taken together, PPARG promotes apoptosis and suppresses the migration and proliferation of ccRCC cells by inhibiting Six2. These findings reveal that the PPARG/Six2 axis acts as a central pathobiological mediator of ccRCC formation and as a potential therapeutic target for the treatment of patients with ccRCC.

Utilization of NGS technologies to investigate transcriptomic and epigenomic mechanisms in trastuzumab resistance

NGS (Next Generation Sequencing) technologies allows us to determine key gene expression signatures that correlate with resistance (and responsiveness) to anti-cancer therapeutics. We have undertaken a transcriptomic and chromatin immunoprecipitation followed by sequencing (ChIP-seq) approach to describe differences in gene expression and the underlying chromatin landscape between two representative HER2+ cell lines, one of which is sensitive (SKBR3) and the other which is resistant (JIMT1) to trastuzumab. We identified differentially expressed genes (DEGs) and differentially expressed transcripts (DETs) between SKBR3 and JIMT1 cells. Several of the DEGs are components of the Polycomb Repressing Complex 2 (PRC2), and they are expressed higher in JIMT1 cells. In addition, we utilized ChIP-seq to identify H3K18ac, H3K27ac and H3K27me3 histone modifications genome-wide. We identified key differences of H3K18ac and H3K27ac enrichment in regulatory regions, found a correlation between these modifications and differential gene expression and identified a transcription factor binding motif for LRF near these modifications in both cell lines. Lastly, we found a small subset of genes that contain repressive H3K27me3 marks near the gene body in SKBR3 cells but are absent in JIMT1. Taken together, our data suggests that differential gene expression and trastuzumab responsiveness in JIMT1 and SKBR3 is determined by epigenetic mechanisms.

Transcriptional factor six2 promotes the competitive endogenous RNA network between CYP4Z1 and pseudogene CYP4Z2P responsible for maintaining the stemness of breast cancer cells

BACKGROUND

The expression of CYP4Z1 and the pseudogene CYP4Z2P has been shown to be specifically increased in breast cancer by our group and others. Additionally, we previously revealed the roles of the competitive endogenous RNA (ceRNA) network mediated by these genes (ceRNET_CC) in breast cancer angiogenesis, apoptosis, and tamoxifen resistance. However, the roles of ceRNET_CC in regulating the stemness of breast cancer cells and the mechanisms through which ceRNET_CC is regulated remain unclear.

METHODS

Transcriptional factor six2, CYP4Z1-3'UTR, and CYP4Z2P-3'UTR were stably overexpressed or knocked down in breast cancer cells via lentivirus infection. ChIP-sequencing and RNA-sequencing analysis were performed to reveal the mechanism through which ceRNET_CC is regulated and the transcriptome change mediated by ceRNET_CC. Clinical samples were used to validate the correlation between six2 and ceRNET_CC. Finally, the effects of the six2/ceRNET_CC axis on the stemness of breast cancer cells and chemotherapy sensitivity were evaluated by in vitro and in vivo experiments.

RESULTS

We revealed that ceRNET_CC promoted the stemness of breast cancer cells. Mechanistically, six2 activated ceRNET_CC by directly binding to their promoters, thus activating the downstream PI3K/Akt and ERK1/2 pathways. Finally, we demonstrated that the six2/ceRNET_CC axis was involved in chemoresistance.

CONCLUSIONS

Our results uncover the mechanism through which ceRNET_CC is regulated, identify novel roles for the six2/ceRNET_CC axis in regulating the stemness of breast cancer cells, and propose the possibility of targeting the six2/ceRNET_CC axis to inhibit breast cancer stem cell (CSC) traits.

Transcriptome profiling of caspase-2 deficient EμMyc and Th-MYCN mouse tumors identifies distinct putative roles for caspase-2 in neuronal differentiation and immune signaling

Caspase-2 is a highly conserved cysteine protease with roles in apoptosis and tumor suppression. Our recent findings have also demonstrated that the tumor suppression function of caspase-2 is context specific. In particular, while caspase-2 deficiency augments lymphoma development in the EμMyc mouse model, it leads to delayed neuroblastoma development in Th-MYCN mice. However, it is unclear how caspase-2 mediates these differential outcomes. Here we utilized RNA sequencing to define the transcriptomic changes caused by caspase-2 (Casp2^−/−) deficiency in tumors from EμMyc and Th-MYCN mice. We describe key changes in both lymphoma and neuroblastoma-associated genes and identified differential expression of the EGF-like domain-containing gene, Megf6, in the two tumor types that may contribute to tumor outcome following loss of Casp2. We identified a panel of genes with altered expression in Th-MYCN/Casp2^−/− tumors that are strongly associated with neuroblastoma outcome, with roles in melanogenesis, Wnt and Hippo pathway signaling, that also contribute to neuronal differentiation. In contrast, we found that key changes in gene expression in the EμMyc/Casp2^−/− tumors, are associated with increased immune signaling and T-cell infiltration previously associated with more aggressive lymphoma progression. In addition, Rap1 signaling pathway was uniquely enriched in Casp2 deficient EμMyc tumors. Our findings suggest that Casp2 deficiency augments immune signaling pathways that may be in turn, enhance lymphomagenesis. Overall, our study has identified new genes and pathways that contribute to the caspase-2 tumor suppressor function and highlight distinct roles for caspase-2 in different tissues.

Regulation of cancer stem cell properties by SIX1, a member of the PAX-SIX-EYA-DACH network

The PAX-SIX-EYA-DACH network (PSEDN) is a central developmental transcriptional regulatory network from Drosophila to humans. The PSEDN is comprised of four conserved protein families; including paired box (PAX), sine oculis (SIX), eyes absent (EYA), and dachshund (DACH). Aberrant expression of PSEDN members, particularly SIX1, has been observed in multiple human cancers, where SIX1 expression correlates with increased aggressiveness and poor prognosis. In conjunction with its transcriptional activator EYA, the SIX1 transcription factor increases cancer stem cell (CSC) numbers and induces epithelial-mesenchymal transition (EMT). SIX1 promotes multiple hallmarks and enabling characteristics of cancer via regulation of cell proliferation, senescence, apoptosis, genome stability, and energy metabolism. SIX1 also influences the tumor microenvironment, enhancing recruitment of tumor-associated macrophages and stimulating angiogenesis, to promote tumor development and progression. EYA proteins are multifunctional, possessing a transcriptional activation domain and tyrosine phosphatase activity, that each contributes to cancer stem cell properties. DACH proteins function as tumor suppressors in solid cancers, opposing the actions of SIX-EYA and reducing CSC prevalence. Multiple mechanisms can lead to increased SIX1 expression, including loss of SIX1-targeting tumor suppressor microRNAs (miRs), whose expression correlates inversely with SIX1 expression in cancer patient samples. In this review, we discuss the major mechanisms by which SIX1 confers CSC and EMT features and other important cancer cell characteristics. The roles of EYA and DACH in CSCs and cancer progression are briefly highlighted. Finally, we summarize the clinical significance of SIX1 in cancer to emphasize the potential therapeutic benefits of effective strategies to disrupt PSEDN protein interactions and functions.

Progression and prognostic value of ECT2 in non-small-cell lung cancer and its correlation with PCNA

Purpose

Epithelial cell transforming sequence 2 (ECT2) is a guanine nucleotide exchange factor, which is involved in cell division regulation and cell cycle modulation. Recent evidence indicates that ECT2 is overexpressed in many human cancers. However, the exact prognostic value of ECT2 in lung cancer has not been elucidated.

Patients and methods

In the current study, we performed correlation and prognosis analyses using public databases and conducted immunohistochemical staining in tissue microarrays, using samples from 204 lung cancer patients with survival data.

Results

We found that the expression of ECT2 was markedly increased in lung cancer tissues compared with normal tissues. Moreover, we demonstrated that the expression of ECT2 was related to tumor cell differentiation degree, TNM stage, lymph node metastasis, and prognosis in non-small-cell lung cancer (NSCLC). A correlation analysis indicated that ECT2 levels were significantly correlated with proliferating cell nuclear antigen (PCNA) levels in NSCLC. Furthermore, Kaplan–Meier analyses revealed that high ECT2 expression was associated with unfavorable overall survival (OS) and progression-free survival (PFS) in NSCLC patients.

Conclusion

Taken together, these results indicate that the overexpression of ECT2 contributes to tumor invasion and progression, suggesting that ECT2 is a potential prognostic marker for NSCLC patients.

Molecular Changes of Lung Malignancy in HIV Infection

Malignancy of the lung is a major source of morbidity and mortality in persons with human immunodeficiency virus infection; as the most prevalent non-acquired immunodeficiency syndrome-defining malignancy, it represents an important and growing problem confronting HIV-infected patients. To evaluate the molecular changes of lung malignancy in HIV infection, we analyzed differential gene expression profiles and screened for early detection biomarkers of HIV-associated lung cancer using Affymetrix arrays and IPA analysis. A total of 59 patients were diagnosed with HIV-associated lung cancer from Jan 2010 to May 2018. The primary outcome was a significant difference in survival outcome between stages III-IV (10.46 ± 1.87 months) and I-II (17.66 ± 2.88 months). We identified 758 differentially expressed genes in HIV-associated lung cancer. The expression levels of SIX1 and TFAP2A are specifically increased in HIV-associated lung cancer and are associated with poorly differentiated tumor tissue. We also found decreased ADH1B, INMT and SYNPO2 mRNA levels in HIV lung cancer. A comprehensive network and pathway analysis of the dysregulated genes revealed that these genes were associated with four network functions and six canonical pathways relevant to the development of HIV-associated lung cancer. The molecular changes in lung malignancy may help screen the growing population of HIV patients who have or will develop this malignancy.

Dachshund 1 is Differentially Expressed Between Male and Female Breast Cancer: A Matched Case-Control Study of Clinical Characteristics and Prognosis

INTRODUCTION

Male breast cancer (MBC) is rare and little is known about its biological behavior. In this study we described clinical characteristics and prognosis of MBC and evaluated roles of different factors between MBC and female breast cancer (FBC).

PATIENTS AND METHODS

We retrospectively reviewed 42 MBC patients matched with 84 consecutive FBC patients with similar year, age, tumor, node, metastases (TNM) stage, and estrogen receptor (ER) expression from 2003 to 2016. Their clinical characteristics, treatments, and prognosis were analyzed, and immunohistochemistry for androgen receptor (AR), dachshund 1 (DACH1), sine oculis 1 (SIX1), eyes absent 1, B-cell lymphoma-2, and p53 were performed on paraffin sections.

RESULTS

MBC constituted 0.56% (42 of 7561) of consecutive breast cancer and had a median age of 55 years. The 14 paraffin samples from men and 28 from women expressed all the assessed proteins, and DACH1 was significantly higher in women (P = .043). Body mass index (P = .023) and DACH1 (P = .034) were correlated with MBC prognosis, whereas the expression of AR (P = .049), SIX1 (P = .048), surgery (P < .001), and chemotherapy (P = .001) were important for FBC in addition to already known factors: tumor size and location, TNM stage (lymph nodes and organ metastasis), radiotherapy, and ER and human epidermalgrowth factor receptor-2 (HER2) expression. No distinct difference in recurrence was observed between MBC and FBC (P = .667).

CONCLUSION

In this study we found that DACH1 was expressed less in MBC and HER2 was expressed more in FBC. They were respectively correlated with MBC and FBC prognosis. Although no significant differences were observed between MBC and FBC prognosis, DACH1, SIX1, and AR expression requires greater attention to develop treatment strategies for MBC and FBC.

MAT1 correlates with molecular subtypes and predicts poor survival in breast cancer

Objective

Menage a trois 1 (MAT1) is a targeting subunit of cyclin-dependent kinase-activating kinase and general transcription factor IIH kinase, which modulates cell cycle, transcription and DNA repair. Its dysregulation is responsible for diseases including cancers. To further explore the role of MAT1 in breast cancer, we investigated the pathways in which MAT1 might be involved, the association between MAT1 and molecular subtypes, and the role of MAT1 in clinical outcomes of breast cancer patients.

Methods

We conducted immunohistochemistry staining on tissue microarray and immunofluorescence staining on sections of MAT1 stable breast cancer cells. Also, we performed Kyoto Encyclopedia of Genes and Genomes pathway analysis, correlation analysis and prognosis analysis on public databases.

Results

MAT1 was involved in multiple pathways including normal physiology signaling and disease-related signaling. Furthermore, MAT1 positively correlated with the protein status of estrogen receptor and progesterone receptor, and was enriched in luminal-type and human epidermal growth factor receptor 2-enriched breast cancer in comparison with basal-like subtype at both mRNA and protein levels. Correlation analysis revealed significant association between MAT1 mRNA amount and epithelial markers, mesenchymal markers, cancer stem cell markers, apoptosis markers, transcription markers and oncogenes. Consistently, the results of immunofluorescence stain indicated that MAT1 overexpression enhanced the protein abundance of epidermal growth factor receptor, vimentin, sex determining region Y-box 2 and sine oculis homeobox homolog 1. Importantly, Kaplan-Meier Plotter analysis reflected that MAT1 could serve as a prognostic biomarker predicting worse relapse-free survival and metastasis-free survival.

Conclusions

MAT1 is correlated with molecular subtypes and is associated with unfavorable prognosis for breast cancer patients.

The Homeotic Protein SIX3 Suppresses Carcinogenesis and Metastasis through Recruiting the LSD1/NuRD(MTA3) Complex

The homeodomain transcription factor SIX3 was recently reported to be a negative regulator of the Wnt pathway and has an emerging role in cancer. However, how SIX3 contributes to tumorigenesis and metastasis is poorly understood.

METHODS

We employed affinity purification and mass spectrometry (MS) to identify the proteins physically associated with SIX3. Genome-wide analysis of the SIX3/LSD1/NuRD(MTA3) complex using a chromatin immunoprecipitation-on-chip approach identified a cohort of target genes including WNT1 and FOXC2, which are critically involved in cell proliferation and epithelial-to-mesenchymal transition. Also, we used flow cytometry, growth curve analysis, EdU incorporation assay, colony formation assays, trans-well invasion assays, immunohistochemical staining and in vivo bioluminescence assay to investigate the function of SIX3 in tumorigenesis.

RESULTS

We demonstrate that the SIX3/LSD1/NuRD(MTA3) complex inhibits carcinogenesis in breast cancer cells and suppresses metastasis in breast cancer. SIX3 expression is downregulated in various human cancers and high SIX3 is correlated with improved prognosis.

CONCLUSION

Our study revealed an important mechanistic link between the loss of function of SIX3 and tumor progression, identified a molecular basis for the opposing actions of MTA1 and MTA3, and may provide new potential prognostic indicators and targets for cancer therapy.

The clinical significance of CXCL5 in non-small cell lung cancer

As a CXC-type chemokine, ENA78/CXCL5 is an important attractant for granulocytes by binding to its receptor CXCR2. Recent studies proved that CXCL5/CXCR2 axis plays an oncogenic role in many human cancers. However, the exact clinical significance of CXCL5 in lung cancer has not been well defined. Here, we found that the serum protein expression of CXCL5 was significantly increased in non-small cell lung cancer (NSCLC) compared with that in healthy volunteers. Immunohistochemistry staining revealed that CXCL5 protein was higher in various lung cancer tissues compared with normal tissues. Moreover, CXCL5 expression correlated with histological grade, tumor size, and TNM stage in NSCLC. Elevated CXCL5 protein abundance predicted poor overall survival in adenocarcinoma patients. Further meta-analysis demonstrated that CXCL5 mRNA expression was also positively associated with tumor stage, lymph node metastasis, and worse survival. Kaplan–Meier plot analyses indicated high CXCL5 was associated with short overall survival and progression-free survival. Together, these results indicated that CXCL5 may be a potential biomarker for NSCLC.

Microarray analyses reveal genes related to progression and prognosis of esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma is a high morbidity and mortality cancer in China. Here are few biomarkers and therapeutic targets. Our study was aimed to identify candidate genes correlated to ESCC. Oncomine, The Cancer Genome Atlas, Gene Expression Omnibus were retrieved for eligible ESCC data. Deregulated genes were identified by meta-analysis and validated by an independent dataset. Survival analyses and bioinformatics analyses were used to explore potential mechanisms. Copy number variant analyses identified upstream mechanisms of candidate genes. In our study, top 200 up/down-regulated genes were identified across two microarrays. A total of 139 different expression genes were validated in GSE53625. Survival analysis found that nine genes were closely related to prognosis. Furthermore, Gene Ontology analyses and Kyoto Encyclopedia of Genes and Genomes analyses showed that different expression genes were mainly enriched in cell division, cell cycle and cell-cell adhesion pathways. Copy number variant analyses indicated that overexpression of ECT2 and other five genes were correlated with copy number amplification. The current study demonstrated that ECT2 and other eight candidate genes were correlated to progression and prognosis of esophageal squamous cell carcinoma, which might provide novel insights to the mechanisms.

DACH1 suppresses breast cancer as a negative regulator of CD44

Dachshund homolog 1 (DACH1), a key cell fate determination factor, contributes to tumorigenesis, invasion, metastasis of human breast neoplasm. However, the exact molecular mechanisms for the anti-tumor roles of DACH1 in breast carcinoma are still lack of extensive understanding. Herein, we utilized immunohistochemistry (IHC) staining and public microarray data analysis showing that DACH1 was higher in normal breast, low-grade and luminal-type cancer in comparison with breast carcinoma, high-grade and basal-like tumors respectively. Additionally, both correlation analysis of public databases of human breast carcinoma and IHC analysis of mice xenograft tumors demonstrated that DACH1 inversely related to cancer stem cells (CSCs) markers, epithelial-mesenchymal transition (EMT) inducers and basal-enriched molecules, while cluster of differentiation 44 (CD44) behaved in an opposite manner. Furthermore, mice transplanted tumor model indicated that breast cancer cells Met-1 with up-regulation of DACH1 were endowed with remarkably reduced potential of tumorigenesis. Importantly, meta-analysis of 19 Gene Expression Omnibus (GEO) databases of breast cancer implicated that patients with higher DACH1 expression had prolonged time to death, recurrence and metastasis, while CD44 was a promising biomarker predicting worse overall survival (OS) and metastasis-free survival (MFS). Collectively, our study indicated that CD44 might be a novel target of DACH1 in breast carcinoma.

SIX3, a tumor suppressor, inhibits astrocytoma tumorigenesis by transcriptional repression of AURKA/B

BACKGROUND

SIX homeobox 3 (SIX3) is a member of the sine oculis homeobox transcription factor family. It plays a vital role in the nervous system development. Our previous study showed that the SIX3 gene is hypermethylated, and its expression is decreased in astrocytoma, but the role of SIX3 remains unknown.

METHODS

Chromatin-immunoprecipitation (ChIP) and luciferase reporter assay were used to confirm the binding of SIX3 to the promoter regions of aurora kinase A (AURKA) and aurora kinase B (AURKB). Confocal imaging and co-immunoprecipitation (Co-IP) were used to detect the interaction between AURKA and AURKB. Flow cytometry was performed to assess the effect of SIX3 on cell cycle distribution. Colony formation, EdU incorporation, transwell, and intracranial xenograft assays were performed to demonstrate the effect of SIX3 on the malignant phenotype of astrocytoma cells.

RESULTS

SIX3 is identified as a novel negative transcriptional regulator of AURKA and AURKB, and it decreases the expression of AURKA and AURKB in a dose-dependent manner in astrocytoma cells. Importantly, interactions between AURKA and AURKB stabilize and protect AURKA/B from degradation, and overexpression of SIX3 does not affect these interactions; SIX3 also acts as a tumor suppressor, and it increases p53 activity and expression at the post-translational level by the negative regulation of AURKA or AURKB, reduces the events of numerical centrosomal aberrations and misaligned chromosomes, and significantly inhibits the proliferation, invasion, and tumorigenesis of astrocytoma in vitro and in vivo. Moreover, experiments using primary cultured astrocytoma cells indicate that astrocytoma patients with a low expression of SIX3 and mutant p53 are more sensitive to treatment with aurora kinase inhibitors.

CONCLUSION

SIX3 is a novel negative transcriptional regulator and acts as a tumor suppressor that directly represses the transcription of AURKA and AURKB in astrocytoma. For the first time, the functional interaction of AURKA and AURKB has been found, which aids in the protection of their stability, and partially explains their constant high expression and activity in cancers. SIX3 is a potential biomarker that could be used to predict the response of astrocytoma patients to aurora kinase inhibitors.

SIX4 promotes metastasis via activation of the PI3K-AKT pathway in colorectal cancer

Background

Several studies report aberrant expression of sine oculis homeobox (SIX) homolog family members during cancer development and progression. SIX4 participates in organ development, such as myogenesis and neurogenesis. However, the expression and clinical implication of SIX4 in colorectal cancer (CRC) remains unclear.

Methods

The SIX4 expression levels in colorectal patients were assessed in nine different human cancer arrays and compared using patient survival data. SIX4 expression was silenced in two cell culture lines for invasion and wound healing assessment. Finally, bioinformatics assessments ascertained the pathways impacted by SIX4.

Results

SIX4 was upregulated in The Cancer Genome Atlas CRC cohort and other gene expression omnibus (GEO) cohorts. In addition, SIX4 expression significantly correlated with lymph node metastasis and advanced Tumor Node Metastasis (TNM) stages. Moreover, SIX4 overexpression was related to unfavorable prognosis in CRC patients. Silencing SIX4 inhibited CRC cell metastasis by surpressing AKT phosphorylation.

Discussion

SIX4 is upregulated in CRC and can be used as a prognosis biomarker.

Recent advances of highly selective CDK4/6 inhibitors in breast cancer

Uncontrolled cell division is the hallmark of cancers. Full understanding of cell cycle regulation would contribute to promising cancer therapies. In particular, cyclin-dependent kinases 4/6 (CDK4/6), which are pivotal drivers of cell proliferation by combination with cyclin D, draw more and more attention. Subsequently, extensive studies were carried out to explore drugs inhibiting CDK4/6 and assess the efficacy and safety of these drugs in cancer, especially breast cancer. Due to the insuperable adverse events and the less activity observed in vivo, the drug development of the initial pan-CDK inhibitor flavopiridol was consequently discontinued, and then highly specific inhibitors were extensively researched and developed, including palbociclib (PD0332991), ribociclib (LEE011), and abemaciclib (LY2835219). Food and Drug Administration has approved palbociclib and ribociclib for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced or metastatic breast cancer, and recent clinical trial data suggest that palbociclib significantly improved clinical outcome when combined with letrozole or fulvestrant. Besides, the favorable effects of abemaciclib on prolonging survival of breast cancer patients have also been observed in clinical trials both for single-agent and combination strategy. In this review, we outline the preclinical and clinical advancement of these three orally bioavailable and highly selective CDK4/6 inhibitors in breast cancer.

BGRMI: A method for inferring gene regulatory networks from time-course gene expression data and its application in breast cancer research

Reconstructing gene regulatory networks (GRNs) from gene expression data is a challenging problem. Existing GRN reconstruction algorithms can be broadly divided into model-free and model–based methods. Typically, model-free methods have high accuracy but are computation intensive whereas model-based methods are fast but less accurate. We propose Bayesian Gene Regulation Model Inference (BGRMI), a model-based method for inferring GRNs from time-course gene expression data. BGRMI uses a Bayesian framework to calculate the probability of different models of GRNs and a heuristic search strategy to scan the model space efficiently. Using benchmark datasets, we show that BGRMI has higher/comparable accuracy at a fraction of the computational cost of competing algorithms. Additionally, it can incorporate prior knowledge of potential gene regulation mechanisms and TF hetero-dimerization processes in the GRN reconstruction process. We incorporated existing ChIP-seq data and known protein interactions between TFs in BGRMI as sources of prior knowledge to reconstruct transcription regulatory networks of proliferating and differentiating breast cancer (BC) cells from time-course gene expression data. The reconstructed networks revealed key driver genes of proliferation and differentiation in BC cells. Some of these genes were not previously studied in the context of BC, but may have clinical relevance in BC treatment.

The expression profile and clinic significance of the SIX family in non-small cell lung cancer

BACKGROUND

The SIX family homeobox genes have been demonstrated to be involved in the tumor initiation and progression, but their clinicopathological features and prognostic values in non-small cell lung cancer (NSCLC) have not been well defined. We analyzed relevant datasets and performed a systemic review and a meta-analysis to assess the profile of SIX family members in NSCLC and evaluate their importance as biomarkers for diagnosis and prediction of NSCLC.

METHODS

This meta-analysis included 17 studies with 2358 patients. Hazard ratio (HR) and 95 % confidence interval (CI) were calculated to represent the prognosis of NSCLC with expression of the SIX family genes. Heterogeneity of the ORs and HRs was assessed and quantified using the Cochrane Q and I 2 test. Begg's rank correlation method and Egger's weighted regression method were used to screen for potential publication bias. Bar graphs of representative datasets were plotted to show the correlation between the SIX expression and clinicopathological features of NSCLC. Kaplan-Meier survival curves were used to validate our prognostic analysis by pooled HR.

RESULTS

The systematic meta-analysis unveiled that the higher expressions of SIX1-5 were associated with the greater possibility of the tumorigenesis. SIX4 and SIX6 were linked to the lymph node metastasis (LNM). SIX2, SIX3, and SIX4 were correlated with higher TNM stages. Furthermore, the elevated expressions of SIX2, SIX4, and SIX6 predicted poor overall survival (OS) in NSCLC (SIX2: HR = 1.14, 95 % CI, 1.00-1.31; SIX4: HR = 1.39, 95 % CI, 1.16-1.66; SIX6: HR = 1.18, 95 % CI, 1.00-1.38) and poor relapse-free survival (RFS) in lung adenocarcinoma (ADC) (SIX2: HR = 1.42, 95 % CI, 1.14-1.77; SIX4: HR = 1.52, 95 % CI, 1.09-2.11; SIX6: HR = 1.25, 95 % CI, 1.01-1.56).

CONCLUSIONS

Our report demonstrated that the SIX family members play distinct roles in the tumorigenesis of NSCLC and can be potential biomarkers in predicting prognosis of NSCLC patients.