FSCN1 Promotes Radiation Resistance in Patients With PIK3CA Gene Alteration

Abstract

Radiotherapy is one of the standard treatments for cervical cancer and head and neck cancer. However, the clinical efficacy of this treatment is limited by radioresistance. The discovery of effective prognostic biomarkers and the identification of new therapeutic targets have helped to overcome the problem of radioresistance. In this study, we show that in the context of PIK3CA mutation or amplification, high expression of fascin actin-bundling protein 1 (FSCN1) (using the median as the cut-off value) is associated with poor prognosis and radiotherapy response in cancer patients. Silencing FSCN1 enhances radiosensitivity and promotes apoptosis in cancer cells with PIK3CA alterations, and this process may be associated with the downregulation of YWHAZ. These results reveal that FSCN1 may be a key regulator of radioresistance and could be a potential target for improving radiotherapy efficacy in cervical cancer and head and neck cancer patients with PIK3CA alterations.

Keywords: fascin actin-bundling protein 1; PIK3CA; apoptosis; cervical squamous cell carcinoma; head and neck squamous cell carcinoma.

Figure 1

High expression of FSCN1 is associated with poor prognosis and response to radiotherapy in CESC and HNSC patients with PIK3CA alterations. (A) The frequency of PIK3CA gene alterations in cervical cancer (CESC) and head and neck cancer (HNSC) cases from the cBioPortal database. (B) Kaplan–Meier curve shows the overall survival (OS) rate in CESC and HNSC cases from the TCGA cohort with wild-type PIK3CA or altered PIK3CA. The P values were calculated by log-rank test. (C) The table shows the radiotherapy response in CESC and HNSC with wild-type PIK3CA or altered PIK3CA. (D) The workflow of screening genes that have synthetic lethal interactions with PIK3CA using TCGA Data Portal. (E, F) Kaplan–Meier curve shows that the overall survival (OS) rate was significantly lower in the high FSCN1 group with PIK3CA activation in the TCGA cohort. The median FSCN1 level was chosen as the cut‐off value for separating the FSCN1 high‐level and low-level groups. (G) The expression of FSCN1 in different CESC and HNSC patient groups with or without a complete response to radiotherapy. PIK3CA “wt” or “alt”, PIK3CA wild type or altered (mutated or amplificated); “CR” or “no CR”, complete response or no complete response. Data are presented as means ± SEM.

Figure 2

FSCN1 silencing enhances sensitivity of cancer cells with PIK3CA alterations to IR treatment. (A, B) The expression of FSCN1 in PIK3CA-altered and PIK3CA-wild-type patients from the GEPIA database. (C, D) The knockdown efficiency of siFSCN1s. Relative expression of FSCN1 in HeLa, CaSki, MDA-MB-231, and T47D cells was detected using qRT-PCR. (E, F) Knockdown of FSCN1 sensitizes cancer cells to IR treatment. Colony formation assays of HeLa, CaSki, MDA-MB-231, and T47D cells transfected with FSCN1 siRNA. Surviving fractions were determined based on plating efficiencies. Plating efficiency of Hela, Caski, T47D, MDA-MB-231 is 62.3, 54.16, 63, and 46.16%. Data are presented as the means ± SEM of at least three independent experiments. *P < 0.05; **P < 0.01; ***P < 0.001. NS, not significant.

Figure 3

FSCN1 inhibits apoptosis of cancer cells with PIK3CA alterations. (A) FSCN1-correlated genes were enriched in apoptosis-related pathways in patients with PIK3CA alterations. The plots show the results of GSEA of the apoptosis pathway of the Reactome database. NES, normalized enrichment score; q, false discovery rate; PIK3CA-wt, wild-type PIK3CA; PIK3CA-alt, mutated or amplified PIK3CA. (B) Western blotting analysis of caspase-3 expression in HeLa, CaSki, MDA-MB-231 and T47D cells transduced with FSCN1 siRNA, after 4 Gy IR treatment. Quantified levels of active-caspase-3 are shown. Data are presented as means ± SEM. ***P < 0.001. NS, not significant.

Figure 4

FSCN1 regulates the expression of YWHAZ in cancer cells with PIK3CA alterations. (A) Venn diagram shows FSCN1-correlated genes in CESC and HNSC patients with wild-type or altered PIK3CA. Eleven genes were coexpressed with FSCN1 in the PIK3CA-altered group of cervical cancer and head and neck cancer patients. Pearson correlation coefficient values are shown in the table. (B) Pearson correlation analysis for the expression levels of FSCN1 and YWHAZ. Graphs show a stronger positive correlation between FSCN1 and YWHAZ in patients with altered PIK3CA than in those with wild-type PIK3CA according to TCGA data. (C) Relative expression of YWHAZ analyzed by qRT-PCR in HeLa, CaSki, MDA-MB-231, and T47D cells transduced with FSCN1 siRNAs. (D) Knockdown of YWHAZ sensitizes cancer cells to IR treatment. Colony formation assays of CaSki and T47D cells transfected with YWHAZ siRNA. Surviving fractions were determined based on plating efficiencies. PIK3CA-wt, wild type PIK3CA; PIK3CA-alt, mutated or amplificated PIK3CA. For (C, D), data are presented as the means ± SEM of at least three independent experiments. *P < 0.05; **P < 0.01; ***P < 0.001. NS, not significant.

Figure 5

Model of mechanisms of FSCN1 in PIK3CA-altered tumor cells.