Elsevier

Tissue and Cell

Volume 75, April 2022, 101708
Tissue and Cell

Actin-like protein 8, a member of cancer/testis antigens, supports the aggressive development of oral squamous cell carcinoma cells via activating cell cycle signaling

https://doi.org/10.1016/j.tice.2021.101708Get rights and content

Highlights

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    ACTL8 is up-regulated in OSCC tissues and cell lines.

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    Knockdown of ACTL8 inhibits the growth and mobility of OSCC cells.

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    There is a significant correlation between ACTL8 expression and tumor status.

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    ACTL8 expression is negatively associated with OSCC prognosis.

Abstract

Due to the malignancy of oral squamous cell carcinoma (OSCC), investigations of novel therapeutic targets and prognostic biomarkers are urgently needed. In our present study, significant up-regulation of Actin-like protein 8 (ACTL8) in OSCC patients was observed by bioinformatics analysis with RNA sequencing data obtained from The Cancer Genome Atlas (TCGA) database. The results of Chi-square test revealed that there was a significant correlation between ACTL8 expression and tumor status (T1 + T2/T3+T4) (P = 0.004). Survival analysis indicated a negative correlation between ACTL8 overexpression and prognosis in OSCC (P = 3.984e-02). An ACTL8 knockdown experiment was conducted to evaluate the function of ACTL8 on OSCC cell biological behaviors. The results revealed that knockdown of ACTL8 significantly inhibited the growth and mobility, arrested cell cycle and promoted apoptosis of TCA-83 and CAL27 cells. Moreover, Gene Set Enrichment Analysis (GSEA) and western blots demonstrated that activation of cell cycle signaling pathway was inhibited by knockdown of ACTL8, as we observed the down-regulation of 4 key proteins (CDK1, cyclin E1, cyclin B2 and c-Myc) in this pathway. The present investigation indicates that ACTL8 plays an oncogenic role in the pathogenesis of OSCC, suggesting that ACTL8 may be a promising therapeutic target and prognosis marker for human OSCC.

Introduction

As one of the most common and malignant cancer, oral squamous cell carcinoma (OSCC) accounts for more than 90 % of oral cancer cases and mostly caused by drinking and smoking (Yamashita et al., 2014; Chinn and Myers, 2015; Tandon et al., 2017). OSCC commonly occurs in mouth and lips, which led to a global death of 177,384 in 2018 (Bray et al., 2018). With accounting for 2ā€“4 % of all malignant cancers, OSCC has become a severe public health issue in the world (Siegel et al., 2020; Chinn and Myers, 2015). At present, surgical removal and radiotherapy are the most common treatments for patients. Despite the more advanced clinical treatments, the survival rate at five years is only about 65 % for patients due to recurrence and metastasis (Michikawa et al., 2012). Thus, to improve treatments of OSCC, accumulating investigations focused on identifying the molecular biomarkers, which may contribute to OSCC molecular targeted therapy (Kim et al., 2019; Wen et al., 2020).

Cancer/Testis antigens (CTAs) are a large group of cancer-related antigens with high expression in some malignant tumors (Serrano et al., 1999). At present, there are more than 200 CTAs identified in mammalian genome (Kulkarni et al., 2012). As up-regulation of CTAs is a common feature of tumor cells, extensive findings support CTAs as the biomarkers and therapeutic targets for many cancers, especially melanoma (Kulkarni et al., 2012). Actin-like protein 8 (ACTL8), also known as Cancer/Testis Antigen 57 (CT57), is a member of the CTAs. A number of investigations have demonstrated that overexpression of ACTL8 promoted cell mobility and attenuated prognosis of lung adenocarcinoma (Ma et al., 2020), endometrial cancer (Li et al., 2020), colorectal cancer (Mao et al., 2019) and head and neck squamous cell carcinoma (Jia et al., 2019). ACTL8 was proved to be expressed in glioblastoma in spite of no expression in normal brain (Freitas et al., 2013). Moreover, by screening genes in OSCC with bioinformatics analysis, ACTL8 was observed to be upregulated in OSCC (Wu et al., 2019). However, the biological function and prognostic value of ACTL8 in OSCC have never been reported.

In this study, significant up-regulation of ACTL8 in OSCC and the significant association between ACTL8 and poor prognosis of OSCC were observed. The viability and mobility of OSCC cells were assessed by CCK8 and Transwell assays in ACTL8 siRNA transfected cells. Furthermore, to explore the mechanism of how ACTL8 regulated the progression of OSCC cells, the protein expression levels of key genes in cell cycle signaling pathway were determined. Our results implicated that ACTL8 may contribute to malignant development of OSCC cells via cell cycle signaling pathway and could be considered as a potential therapeutic target and prognosis marker for human OSCC.

Section snippets

Bioinformatics analysis

The RNA sequencing (RNA-seq) data and clinical information of 370 samples (338 OSCC samples and 32 normal samples) were downloaded from The Cancer Genome Atlas (TCGA, https://cancergenome.nih.gov/) database. The biological pathways that associated with ACTL8 expression were analyzed by Gene Set Enrichment Analysis (GSEA).

Cell culture

OSCC cell lines (TCA-83 and CAL 27) are used for study OSCC in many reports (Wang et al., 2016; Guo et al., 2020; Zhou et al., 2021). Further, TCA-83 and CAL27 cell lines could

Up-regulated ACTL8 in OSCC patients can be used as a promising prognostic indicator

RNA-Seq data of 370 samples including in 32 normal oral tissue samples and 338 OSCC tissue samples from TCGA database was analyzed to evaluate the expression level of ACTL8 in OSCC patients. Fig. 1A demonstrated that ACTL8 was significantly highly regulated in OSCC samples compared with the normal oral samples (P = 0.005), which was consistent with the previous study.(Wu et al., 2019)

Next, the clinical significance of ACTL8 overexpression was assessed. The 266 samples with complete clinical

Discussion

Despite great diagnostic and therapeutic improvements, the survival rate of OSCC patients remains low in the last decades. Even with regular surgical removal and radiotherapy, it still remained a high rate of relapse and metastasis (about 33 %) (Vered et al., 2010). Therefore, the investigations of novel therapeutic targets and prognostic biomarkers are urgently needed.

The tumorigenesis and poor prognosis is associated with the overexpression rather than mutation of CTAs (Kulkarni et al., 2012;

Conclusions

Overall, the overexpression of ACTL8 was notably observed in OSCC and associated with a poor prognosis. ACTL8 might promote the viability, invasive and migratory capacities of OSCC cells via the activation of the cell cycle signaling pathway. Therefore, these results indicated that ACTL8 may be a potential therapeutic target and prognosis marker for human OSCC. It is noteworthy that our investigation offers a new idea for OSCC molecular therapy.

Data availability

No data was used for the research described in the article.

Data will be made available on request.

Author contributions

Lifang Wang (Conceptualization; Data curation; Investigation; Writing - original draft; Writing - review & editing), Xiaoling Xing (Data curation; Formal analysis; Writing - original draft), Hua Tian (Methodology; Project administration), Qingchun Fan (Conceptualization; Writing - review & editing)

Ethical statement

Not Applicable.

Funding statement

No funding.

Declaration of Competing Interest

The authors report no declarations of interest.

Acknowledgements

Not Applicable.

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