Correlation of signal transducer and activator of transcription-3 and β -catenin expression in laryngeal squamous cell carcinoma

Abstract

Objective

The specific roles of phosphorylated signal transducer and activator of transcription-3 (p-STAT3) and β-Catenin in laryngeal squamous cell carcinoma (LSCC) remain unclear.

Methods

In this study, the correlations between p-STAT3, β-Catenin, and clinicopathological characteristics were investigated using tissues and clinical data from 124 LSCC cases. Immunohistochemistry and immunofluorescence assays were used to examine p-STAT3 and β-Catenin expression and localization in these samples. Kaplan–Meier survival and Cox regression analyses were performed to evaluate the prognostic significance of these proteins. LSCC cell lines were treated with a STAT3 inhibitor (dihydroartemisinin) or activator (interleukin-6) to explore the mechanism of p-STAT3 and β-Catenin.

Results

There was an inverse correlation between p-STAT3 and β-Catenin expression in the LSCC samples. Patients with high p-STAT3 and low β-Catenin expression levels had significantly worse overall survival. Multivariate Cox regression analysis revealed that lymph node metastasis and β-Catenin expression were both independently correlated with unfavorable overall survival. Cell treatment with the p-STAT3 inhibitor inhibited the nuclear accumulation of β-Catenin, while p-STAT3 activator treatment could promote β-Catenin translocation to the nucleus.

Conclusion

Overall, our data indicate that p-STAT3 expression is associated with LSCC by promoting β-Catenin degradation.

Keywords

β-Catenin epithelial-mesenchymal transition laryngeal squamous cell carcinoma STAT3 prognostic indicator biomarker

Introduction

Laryngeal cancer is the second most common type of head and neck cancer.¹ A previous study showed that the 5-year survival rate of laryngeal cancer patients decreased from 66% to 63% between 1975 and 2011.² Prior reports have suggested that tumor metastasis, a complex and dynamic process that involves tumor cells spreading from the primary site, is the main hurdle preventing improved laryngeal cancer patient outcomes. Signal transducer and activator of transcription-3 (STAT3) is a transcription factor that is activated by various cytokines and growth factors and can play essential roles in cell proliferation, invasion, angiogenesis, and distant metastasis.³ For example, STAT3 can induce hepatocellular carcinoma metastasis by mediating the epithelial-mesenchymal transition (EMT).⁴ Moreover, downregulation of STAT3 expression could reduce breast cancer tumorigenicity, growth, and metastasis.⁵

Loss of intercellular adhesion is a crucial prerequisite related to tumor invasion and metastasis.⁶ β-Catenin is a pivotal adhesion-related factor, and its abnormal regulation has been associated with the initiation and progression of various types of malignancies.⁷ Studies have shown that reduced β-Catenin expression is a predictive marker for lymph node metastasis in head and neck squamous cell carcinoma.^8,9 Kudo et al. demonstrated that reduced β-Catenin expression levels were more likely to be found on the cell membrane side of the invasion and metastasis area in oral squamous cell carcinoma.¹⁰ Prior research indicated that the expression of phosphorylated STAT3 (p-STAT3) was closely related to the nuclear expression of β-Catenin in colorectal cancer.¹¹ Moreover, STAT3 can exert oncogenic effects in breast cancer by synergistically upregulating the transcriptional activity and expression of β-Catenin.¹² In pancreatic cancer, STAT3 potentially acts as a pivotal component to suppress malignant behaviors by inactivating the Wnt/β-catenin pathway.¹³

To the best of our knowledge, the relationship between p-STAT3 and β-Catenin in laryngeal squamous carcinoma (LSCC) has not been elucidated. Therefore, this study aimed to explore the clinical and prognostic significance of p-STAT3 and β-Catenin in LSCC, then investigate the potential mechanism controlling these proteins.

Materials and methods

Subjects

LSCC patients who received surgical resection at Bethune International Peach Hospital between January 2009 and December 2013 were prospectively enrolled in the present study. All procedures were approved by the Institutional Human Ethics Committee of the Bethune International Peace Hospital (Approval No. 2017-KY-02) and written informed consent was obtained from all participants. All LSCC cases were post-operatively confirmed by pathological examination, and patient clinicopathological data were collected. Patients with any prior treatment, such as radiotherapy, chemotherapy, or biotherapy, or distant metastasis were excluded from this study.

The tumors were also staged according to the tumor, node, metastasis (TNM) system of the International Union against Cancer (UICC 2002) after surgical resection. All patients were followed-up until all-cause mortality or the last follow-up. The period of time (months) from the time of surgical resection to death (or the last follow-up) was defined as overall survival (OS).

Immunohistochemistry (IHC)

Formalin-fixed, paraffin-embedded tissues were cut into 3-μm-thick sections and deparaffinized, rehydrated, and subjected to antigen retrieval. The sections were then incubated with primary antibodies against p-STAT3 (tyrosine 705, 1:50, Abcam, Cambridge, UK) or β-Catenin (1:100, Abcam) at 4°C overnight. After washing, all reactions were continued using the Vectastain ABC Kit (Vector Laboratories, Burlingame, CA, USA). The sections were then counterstained with hematoxylin.

Evaluation of p-STAT3 and β-Catenin protein expression in LSCC samples were scored and calculated for 10 randomly selected areas as the cross-product of the staining intensity value and the proportion of positively stained cells, as previously reported.¹⁴ The percentage of positively stained cells was scored with a five-tiered approach: score 0 = negative; score 1 =<10% but >0% positively stained cells, score 2 = 10% to 50% positively stained cells; score 3 = 51% to 80% positively stained cells; score 4 = >80% positively stained cells. Similarly, the staining intensity was divided into four grades: 0, negative; 1, mildly stained; 2, moderately stained; and 3, intensively stained.

Cell culture and main reagents

The human LSCC cell line Hep-2 was purchased from the American Type Culture Collection (Manassas, VA, USA) and cultured in RPMI-1640 medium supplemented with 10% fetal bovine serum (Gibco, Rockville, MD, USA) and 1% penicillin and streptomycin (Gibco) at 37°C, 5% CO₂, and 95% humidity. Dihydroartemisinin (DHA; Tci, Tokyo, Japan), an inhibitor of STAT3,¹⁵ was dissolved in dimethyl sulfoxide (DMSO; Sigma-Aldrich, St. Louis, MO, USA) and stored as a 200-mmol/L stock solution at −20°C. STAT3 activator interleukin (IL)-6 was commercially obtained from PeproTech (Rocky Hill, NJ, USA). The cells were treated with DHA for 24 hours and/or IL-6 for 1 hour. Monoclonal antibodies against p-STAT3 (Tyr705), E-cadherin, N-cadherin, Vimentin, glycogen synthase kinase (GSK)-3β, p-β-Catenin, and matrix metalloproteinase 9 (MMP-9) were purchased from Cell Signaling Technology (CST; Danvers, MA, USA), and an antibody against β-Catenin was obtained from Abcam.

MTT assay

Hep-2 cells were seeded in 96-well plates (1 × 10⁴ cells/well) and incubated overnight, followed by treatment with DHA at different concentrations (2.5, 5, 10, 20, 40, or 80 μM) for 24 hours. After incubation, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) (20 μL; 5 mg/mL; Sigma-Aldrich) was added to each well and incubated for an additional 4 hours at 37°C. DMSO (150 μL/well) was then added, and the plates were examined with an Enzyme-linked Immunosorbent Detector (Model 550, Bio-Rad, Hercules, CA, USA) by measuring absorbance at 490 nm. IC50 values were obtained from the cytotoxicity curves using Graphpad Prism 6 software.

Western blot analysis

Western blots were performed as described previously, with minor modifications.¹⁶ Briefly, cultured cells were harvested and lysed in ice-cold lysis buffer. Protein concentrations were determined using the BCA protein assay kit (Pierce Biotechnology Inc., Rockford, IL, USA). Equivalent amounts of proteins were separated using SDS-PAGE and then electroblotted onto a polyvinylidene fluoride (PVDF) membrane. The membranes were then blocked in 5% non-fat milk for 1 hour at room temperature and subsequently incubated with the indicated primary antibodies overnight at 4°C. The next day, the membranes were incubated with horseradish peroxidase-conjugated goat anti-mouse or anti-rabbit secondary antibody (Zhongshan Golden Bridge Bio-technology Co., Ltd., Beijing, China) for 1 hour at room temperature. Immunoreactive proteins were visualized with an enhanced chemiluminescence detection system (GE Healthcare Life Sciences, Amersham, UK). β-actin was used as the loading control for western blot analysis (ab8227, Abcam).

Immunofluorescence (IF) assays

IF assays were performed as described previously.¹⁶ In brief, the samples were fixed, permeabilized, blocked, and incubated with primary antibody at 37°C for 1 hour, followed by incubation with the corresponding secondary antibody at 37°C for 1 hour. The primary antibodies used in this study included a rabbit anti-p-STAT3 monoclonal antibody (CST, 1:100) and mouse anti-β-Catenin antibody (Abcam, 1:200). The secondary antibodies included an Alexa Fluor 488-conjugated sheep anti-mouse IgG antibody (Zhongshan Goldenbridge Bio-technology Co., Ltd., 1:400) and AlexaFluor 594-conjugated sheep anti-rabbit antibody (Zhongshan Goldenbridge Bio-technology Co., Ltd., 1:100). Cells were counterstained with 4′, 6-diamidino-2-phenylindole dihydrochloride (DAPI) (10 μg/mL) (Sigma-Aldrich). Images were captured via a fluorescence microscope (Olympus BX51, Tokyo, Japan) and assessed by confocal microscopy.

Statistical analysis

All data were analyzed using SPSS Statistics software (Version 18.0, SPSS Inc., Chicago, IL, USA). The associations between target protein expression levels and clinicopathological factors were analyzed using chi-square and Fischer’s exact tests. The correlation between two parameters was calculated using the Pearson’s correlation coefficient (r) method. Receiver operating characteristic (ROC) curve analysis for LSCC patient survival status was performed to determine the optimal cut-off score for p-STAT3 and β-Catenin expression (Figure 1). For survival analysis, univariate analysis was performed using the Kaplan–Meier method and compared by long-rank test. Multivariate analyses were performed using a Cox proportional hazards model. Two-sided P-values <0.05 were considered statistically significant.

Figure 1.

Receiver operating characteristic (ROC) curves for laryngeal squamous cell carcinoma (LSCC) patient survival status using p-STAT3 or β-Catenin expression. The dotted line indicates β-Catenin and the solid line indicates p-STAT3. The area under the curve (AUC) values for p-STAT3 and β-Catenin are shown.

Results

p-STAT3 and β-Catenin expression patterns in LSCC

Overall, 124 LSCC cases were prospectively enrolled in this study. The patients, aged 40 to 80 years (mean: 63 years), included 121 male patients and 3 female patients. The cases were classified into glottic carcinoma (n = 86), supraglottic carcinoma (n = 36), and subglottic carcinoma (n = 2) according to tumor location.

As shown in Figure 2, p-STAT3 protein was predominantly localized in cell nuclei, while β-Catenin was mainly in the cell membrane. Positive IHC staining for p-STAT3 and β-Catenin were noted in 71 (57.3%) and 57 (46.0%) cases, respectively, among the 124 LSCC tissues (Table 1). Importantly, of the 71 p-STAT3-positive cases, 54 (76.1%) were negative for β-Catenin. Additionally, of the 57 β-Catenin-positive cases, 40 (70.0%) were negative for p-STAT3 (Table 1). A significant inverse correlation between nuclear p-STAT3 staining and membrane β-Catenin staining (r² = 0.1608, P < 0.001, Figure 3) was noted.

Figure 2.

Immunohistochemistry staining results of p-STAT3 and β-Catenin protein expression in laryngeal squamous cell carcinoma (LSCC) tissues (×400). p-STAT3 protein was mainly localized in the cell nucleus, while β-Catenin was localized in the cell membrane. Brown staining is target protein expression and blue staining is hematoxylin counterstaining of the nuclei.

Table 1.

Relationships between the nuclear expression of p-STAT3 and membrane expression of β-catenin in 124 laryngeal squamous cell carcinoma (LSCC) tissues.

β-catenin expression	p-STAT3 expression		Total
β-catenin expression	Negative	Positive	Total
Negative	13	54	67 (54.0%)
Positive	40	17	57 (46.0%)
Total	53 (42.7%)	71 (57.3%)	124 (100.0%)

Figure 3.

The correlation between immunostaining intensity scores of p-STAT3 and β-Catenin in 124 laryngeal squamous cell carcinoma (LSCC) tissues. (a) Representative images of concurrent expression of p-STAT3 and β-Catenin in consecutive tissue sections of two LSCC cases and (b) Linear regression analysis between immunostaining intensity scores of p-STAT3 and β-Catenin.

Relationships between p-STAT3 and β-Catenin expression and LSCC clinicopathological features

As shown in Table 2, significant correlations were found between p-STAT3 expression and T stage, lymph node metastasis, and histological differentiation (P < 0.05). β-Catenin expression was significantly correlated with T stage, lymph node metastasis, TNM stage, and histological differentiation (P < 0.05). Neither p-STAT3 expression nor β-Catenin expression was associated with the LSCC patient’s age, sex, or tumor site.

Table 2.

Expression of p-STAT3 and β-catenin in laryngeal squamous cell carcinoma (LSCC) tissues and the relationships with clinicopathologic factors.

Variable		p-STAT3, n (%)				β-catenin, n (%)
Variable	n	Positive	Negative	Chi-square	P	Positive	Negative	Chi-square	P
Age (years)
≤60	49	28 (57.1)	21 (42.9)	0	0.983	25 (51.0)	24 (49.0)	0.83	0.361
>60	75	43 (57.3)	32 (42.7)			32 (42.7)	43 (57.3)
Sex
Male	121	69 (57.0)	52 (43.0)	0.00	1.00	57 (47.1)	64 (52.9)	1.06	0.303
Female	3	2 (66.7)	1 (33.3)			0 (0)	3 (100)
T Stage
T1/T2	71	35 (49.3)	35 (49.3)	4.30	0.038	40 (56.3)	31 (43.7)	7.19	0.007
T3/T4	53	36 (67.9)	17 (32.1)			17 (32.1)	36 (67.9)
LNM
Negative	94	48 (51.1)	46 (48.9)	6.09	0.014	50 (53.2)	44 (46.8)	8.16	0.004
Positive	30	23 (76.7)	7 (23.3)			7 (23.3)	23 (76.7)
TNM stage
I/II	64	32 (50.0)	32 (50.0)	2.85	0.092	36 (56.3)	28 (43.8)	5.63	0.018
III/IV	60	39 (65.0)	21 (35.0)			21 (35.0)	39 (65.0)
Tumor Site
Supraglottic	36	23 (63.9)	13 (36.1)	0.938	0.629	15 (41.7)	21 (58.3)	0.38	0.826
Glottic	86	47 (54.7)	39 (45.3)			41 (47.7)	45 (52.3)
Subglottic	2	1 (50.0)	1 (50.0)			1 (50.0)	1 (50.0)
Histological Grade
I/II	105	55 (52.4)	50 (47.6)	6.66	0.010	55 (52.4)	50 (47.6)	11.35	0.001
III/IV	19	16 (84.2)	3 (15.8)			2 (10.5)	17 (89.5)

LNM, lymph node metastasis. P < 0.05 was considered statistically significant.

Survival analyses

Kaplan–Meier analysis for p-STAT3 and β-Catenin expression suggested that the median survival time for LSCC patients with p-STAT3-positive staining was significantly shorter than that of the p-STAT3-negative group (Figure 4a, P < 0.01). In comparison, LSCC patients with β-Catenin-positive staining presented with a significantly favorable median survival compared with those with β-Catenin-negative staining (Figure 4b, P < 0.01). Furthermore, LSCC patients with positive p-STAT3 and negative β-Catenin staining had significantly worse OS compared with the other three groups (Figure 4c, P < 0.01).

Figure 4.

Kaplan–Meier analysis of overall survival in 124 laryngeal squamous cell carcinoma (LSCC) patients according to (a) p-STAT3 expression (P < 0.01), (b) β-Catenin expression (P < 0.01) and (c) combined expression of p-STAT3 and β-catenin.

Univariate analysis was first used to assess the impact of various factors on the OS of LSCC patients. The results (Table 3) showed that LSCC patient age, sex, T stage, lymph node metastasis, TNM stage, histological differentiation, p-STAT3 expression, and β-Catenin expression were all significantly associated with OS. The Cox multivariate analysis showed that lymph node metastasis (hazard ratio (HR) = 2.26, 95% confidence interval (CI) = 1.10–4.66, P = 0.027) and β-Catenin expression (HR = 0.36, 95% CI = 0.13–0.98, P = 0.045) were significant independent prognostic indicators for LSCC (Table 3).

Table 3.

Kaplan–Meier survival univariate analysis and Cox regression model overall survival multivariate analysis.

Variables	Univariate analysis				Multivariate analysis
Variables	Median value	95% CI	Chi-square	P	HR	95% CI	P
Age (years)			4.24	0.040	1.34	0.65–2.78	0.427
≤60	–	–
>60	65	–
Sex			9.43	0.002	1.27	0.32–5.00	0.732
Male	–	–
Female	30	0.0–70.0
T Stage			14.75	0.000	1.93	0.44–8.58	0.386
T1/T2	–	–
T3/T4	50	44.9–55.1
LNM			26.12	0.000	2.26	1.10–4.66	0.027
Negative	–	–
Positive	47	37.5–56.5
TNM stage			12.27	0.000	1.03	0.21–5.01	0.967
I/II	–	–
III/IV	53	44.7–61.3
Tumor Site			5.49	0.064	1.02	0.51–2.01	0.963
Supraglottic	57	46.7–67.4
Glottic	–	–
Subglottic	16	–
Histological Grade			8.47	0.004	1.97	1.45–3.18	0.973
I/II	–	–
III/IV	43	14.7–71.3
p-STAT3			18.81	0.000	2.43	0.90–6.54	0.079
Negative	–	–
Positive	57	41.8–72.2
β-catenin			22.13	0.000	0.36	0.13–0.98	0.045
Negative	53	39.5–66.5
Positive	–	–

LNM, lymph node metastasis; CI, confidence interval; HR, hazard ratio. P < 0.05 was considered statistically significant.

Relationship between p-STAT3 and β-Catenin in LSCC cell lines

To investigate the potential relationship between p-STAT3 and β-Catenin, we hypothesized that p-STAT3 inhibitor DHA or activator IL-6 could change the phosphorylation status of β-Catenin.^17,18 We then treated Hep-2 cells with various concentrations (0, 10, 20, 40, or 80 μM) of DHA for 24 hours. The results showed that DHA treatment could decrease the expression of p-STAT3 and β-Catenin and simultaneously increase the expression of GSK-3β and p-β-Catenin (Figure 5). Furthermore, N-cadherin, Vimentin, and MMP-9 protein levels were reduced after DHA treatment, while E-cadherin protein levels increased (Figure 5). Hep-2 cells were then pretreated with 20 ng/mL IL-6 for 1 hour followed by 40 μM DHA treatment for 24 hours. We noted that p-STAT3 and β-Catenin expression levels were upregulated, while GSK-3β and p-β-Catenin expression levels were downregulated. IL-6 possibly activates p-STAT3 and β-Catenin by decreasing the expression of GSK-3β and p-β-Catenin. However, these effects were abrogated by DHA treatment (Figure 6). The localization changes of p-STAT3 and β-Catenin in Hep-2 cells were further confirmed using IF assays. The results indicated that DHA treatment could suppress the translocation of β-Catenin to the nucleus, while IL-6 treatment could promote the translocation (Figure 7).

Figure 5.

Western blot analysis of protein lysates of Hep-2 cells treated with different concentrations of DHA. p-STAT3, β-Catenin, E-Cadherin, N-Cadherin, Vimentin, GSK-3β, p-β-Catenin, and MMP-9 protein expression levels were analyzed. β-actin was used as a loading control.

Figure 6.

Western blot analysis of protein lysates of Hep-2 cells treated with or without 20 ng/mL IL-6 for 1 hour and 40 μM DHA for 24 hours. p-STAT3, β-Catenin, E-Cadherin, N-Cadherin, Vimentin, GSK-3β, MMP-9, and p-β-Catenin protein expression levels were analyzed. β-actin was used as a loading control.

Figure 7.

Localization changes of p-STAT3 and β-Catenin protein in Hep-2 cells. Representative images of immunofluorescence assays (1000×). Hep-2 cells were treated for 24 hours as indicated and analyzed for p-STAT3 (red) or β-Catenin (green) protein expression. Nuclei were counterstained with DAPI (blue).

Discussion

p-STAT3 and β-Catenin have been reported as cellular adhesion-related factors that play roles in human cancers.¹⁹ In the present study, we aimed to evaluate the clinical implications of p-STAT3 and β-Catenin in LSCC and elucidate the potential relationship between them. From the clinical data of 124 LSCC patients, we found that both p-STAT3 and β-Catenin expression were significantly associated with OS. Multivariate analysis revealed that β-Catenin expression and lymph node metastasis were independent prognostic factors for LSCC. Moreover, we observed a significant negative correlation between nuclear p-STAT3 staining and membrane β-Catenin staining in LSCC tissues. In the LSCC cell lines, our results showed that p-STAT3 can negatively regulate β-Catenin expression by promoting its translocation and accumulation in the nucleus, as well as contribute to EMT progression.

STAT3 has previously been noted to be hyperactivated in a variety of human cancers, including LSCC.²⁰ Several studies have suggested that high STAT3 expression levels potentially indicate poor prognosis in some cancers.^21–22 For example, STAT3 was associated with advanced TNM stage and could thus serve as an independent indicator of unfavorable outcomes in gastric cancer.²³ In addition, STAT3 has been found to be involved in the cell motility, metastasis, and progression of human lingual squamous cell carcinoma.²⁴ In our study, nuclear p-STAT3 staining was observed in 54% of the LSCC patient samples examined, and its expression levels were closely related to T stage, lymph node metastasis, and histological differentiation. Moreover, the univariate analysis indicated that p-STAT3 levels could help predict worse survival outcomes for LSCC patients, which was consistent with previous studies. Our results suggested that p-STAT3 plays a crucial role in the differentiation and progression of LSCC.

EMT is a process by which non-motile polar epithelial cells can transform into mesenchymal-like cells under specific physiological or pathological conditions.⁶ Abundant evidence has demonstrated that EMT plays a key role in promoting tumor metastasis.²⁵ Therefore, we hypothesized that p-STAT3 can regulate the EMT process by suppressing β-Catenin expression.

β-Catenin, an important factor in EMT, plays different roles in the progression of various cancers depending on its subcellular localization. It serves as an adhesion molecule when expressed on the cell membrane and as a transcription factor when in the nucleus.²⁶ β-Catenin has mostly been reported to be localized to the nucleus and as a prognostic biomarker.^27–29 In triple-negative breast cancer, reduced membranous expression of β-Catenin was significantly associated with poor overall survival and disease-specific survival.³⁰ A recent meta-analysis showed that both β-Catenin overexpression in the nucleus and reduced membrane expression levels could serve as a valuable prognostic predictor for cervical squamous cell cancer.²⁸ In our study, we detected membrane expression of β-Catenin that was closely related to LSCC T stage, lymph node metastasis, TNM stage, and histological differentiation.

We then further explored the relationship between p-STAT3 and β-Catenin in vitro. We found that the p-STAT3 inhibitor DHA could suppress nuclear accumulation of β-Catenin. In addition, STAT3 was activated by IL-6 treatment and could promote β-Catenin translocation to the nucleus. β-Catenin expression in cancer cells is mainly regulated by the canonical Wnt signaling pathway. There are two predominant theories to explain the β-Catenin degradation process.³¹ One suggests that GSK-3β can directly phosphorylate the N-terminal end of β-Catenin protein, leading to its degradation. The other states that GSK-3β first phosphorylates adenomatous polyposis coli tumor suppressor protein, which supports easier binding to β-Catenin and the following degradation.

We hypothesized that p-STAT3 can regulate β-Catenin activity by controlling the function of GSK-3β in the destruction complex. In this study, when DHA treatment was used to inhibit p-STAT3, the total β-Catenin expression levels were decreased. Compared with its decreased expression levels in the nucleus, β-Catenin membrane expression levels were relatively increased. Simultaneously, the expression of both GSK-3β and p-β-Catenin increased. However, we observed the opposite effects when the cells were treated with IL-6. Our data show that activating p-STAT3 with IL-6 could inhibit GSK-3β expression and reduce β-Catenin phosphorylation, simultaneously causing the accumulation of β-Catenin and translocation to the nucleus. In addition, accumulated β-Catenin can potentially bind to T cell factor/lymphoid enhancing factor-1 in the nucleus and form a complex to initiate the transcription of downstream target genes. This can sequentially promote the development, invasion, and metastasis of LSCC.

Collectively, our results suggest that p-STAT3 and β-Catenin are potential prognostic biomarkers for LSCC. There was a strong association between STAT3 activation and nuclear accumulation of β-Catenin in both human LSCC tissues and LSCC cell lines. In addition, STAT3 possibly induces the degradation of β-Catenin and in turn affect LSCC invasion and metastasis. However, our study also has several limitations. First, the sample size of LSCC cases was relatively small. Moreover, in vivo experiments using animal models are also required to validate and extend our in vitro results.

Conclusion

Taken together, our findings suggest that p-STAT3 and β-Catenin may be novel targets for LSCC therapy. Further elucidating the mechanism of LSCC metastasis will be of great significance for such therapeutic development.

Footnotes

Declaration of conflicting interests

The authors declare that there is no conflict of interest.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by the Hebei Province Graduate Student Innovation Fund Project (No. CXZZBS2017115).

ORCID iD

Xiaoming Li

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