Overexpression of RASAL1 Indicates Poor Prognosis and Promotes Invasion of Ovarian Cancer

Abstract

RAS protein activator like-1 (RASAL1) exists in numerous human tissues and has been commonly demonstrated to act as a tumor suppressor in several cancers. This study aimed to identify the functional characteristics of RASAL1 in ovarian adenocarcinoma and a potential mechanism of action. We analyzed RASAL1 gene expression in ovarian adenocarcinoma samples and normal samples gained from the GEO and Oncomine databases respectively. Then the relationship between RASAL1 expression and overall survival (OS) was assessed using the Kaplan-Meier method. Furthermore, the biological effect of RASAL1 in ovarian adenocarcinoma cell lines was assessed by Quantitative real time-PCR (qRT-PCR), Cell Counting Kit-8 (CCK-8), western blot, wound healing and transwell assay. The statistical analysis showed patients with higher RASAL1 expression correlated with worse OS. The in vitro assays suggested knockdown of RASAL1 could inhibit cell proliferation, cell invasion and migration of ovarian adenocarcinoma. Moreover, the key proteins in the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK) signaling pathway were also decreased in ovarian adenocarcinoma cells with RASAL1 silencing. These findings provide promising evidence that RASAL1 may be not only a powerful biomarker but also an effective therapeutic target of ovarian adenocarcinoma.

Keywords: ERK; RASAL1; invasion; migration; ovarian cancer; poor prognosis; proliferation.

Figure 1

RASAL1 gene expression differences between normal samples and ovarian adenocarcinoma samples (A) RASAL1 gene expression differences between 12 normal samples and 12 ovarian adenocarcinoma samples gained from GEO. **P < 0.01 compared with normal samples. (B) RASAL1 gene expression differences between 10 peritoneum samples and 43 ovarian serous adenocarcinoma samples. **P < 0.01 compared with normal samples.

Figure 2

The overall survival (OS) based on the RASAL1 expression level.

Figure 3

Analysis of RASAL1 expression levels in 2 ovarian adenocarcinoma cell lines (HEY and A2780) compared with normal human ovarian adenocarcinoma cell IOSE80 using qRT-PCR. **P < 0.01 compared with IOSE80.

Figure 4

The relative expression levels of RASAL1 in HEY cells transfected with si-con or si- RASAL1 (si- RASAL11 1# and si- RASAL1 2#) were measured using qPCR and western blot. (A) Relative RASAL1 gene expression measured using qPCR. (B) Relative RASAL1 protein expression measured using western blot. si-con, negative control. **P < 0.01 compared with si-con group.

Figure 5

The proliferation of ovarian adenocarcinoma cell HEY transfected with RASAL1 was inhibited. si-con, negative control. **P < 0.01 compared with si-con group.

Figure 6

The migration and invasion of ovarian adenocarcinoma cell line HEY with knockdown of RASAL1 was inhibited. (A) Wound healing assay was conducted 72 h after transfection to determine the migration ability of HEY cells. (B) Transwell assay was conducted 72 h after transfection to determine the invasion and migration ability of HEY cells. si-con, negative control, **P < 0.01 compared with si-con group.

Figure 7

Knockdown of RASAL1 inhibits the ERK signaling pathway in HEY cells. Expression level of proteins was measured in the HEY cells after 72 h transfection using western blot. si-con, negative control. **P < 0.01 compared with si-con group.