Cytoplasmic Forkhead box M1 (FoxM1) in esophageal squamous cell carcinoma significantly correlates with pathological disease stage

Abstract

Esophageal cancer is a deadly cancer with esophageal squamous cell carcinoma (ESCC) as the major type. Until now there has been a lack of reliable prognostic markers for this malignancy. This study aims to investigate the clinical correlation between Forkhead box M1 (FoxM1)and patients' parameters in ESCC.

Methods: Immunohistochemistry was performed to investigate the expression and localization of FoxM1 in 64ESCC tissues and 10 nontumor esophageal tissues randomly selected from 64 patients before these data were used for clinical correlations.

Results: Cytoplasmic and nuclear expressions of FoxM1 were found in 63 and 16 of the 64 ESCC tissues, respectively.Low cytoplasmic expression of FoxM1 was correlated with early pathological stage in ESCC (P = 0.018),while patients with nuclear FoxM1 were younger in age than those without nuclear expression (P\0.001).Upregulation of FoxM1 mRNA was found in five ESCCcell lines (HKESC-1, HKESC-2, HKESC-3, HKESC-4,and SLMT-1) when compared to non-neoplastic esophageal squamous cell line NE-1 using quantitative polymerase chain reaction (qPCR). Except for HKESC-3, all studied ESCC cell lines demonstrated a high expression of FoxM1 protein using immunoblot. A high mRNA level of FoxM1 was observed in all of the ESCC tissues examined when compared to their adjacent nontumor tissues using qPCR.

Conclusion: Cytoplasmic FoxM1 was correlated with pathological stage and might be a biomarker for advanced ESCC.

Fig. 1

Immunohistochemical staining of FoxM1 in tissue microarray of colorectal cancers. Anti-FoxM1 antibody was used to stain FoxM1 in colorectal cancer tissues from tissue microarray (a). A negative control was included in a parallel experiment (b). Original magnification, 200×

Fig. 2

High mRNA level of FoxM1 in ESCC cell lines. qPCR was performed to investigate the mRNA level of FoxM1 in ESCC cell lines (HKESC-1, HKESC-2, HKESC-3, HKESC-4, and SLMT-1) and the non-neoplastic esophageal cell line NE-1. High mRNA level of FoxM1 was associated with ESCC cells. Each sample was repeated at least in duplicate

Fig. 3

High mRNA level of FoxM1 in ESCC tissues. qPCR was performed to investigate the mRNA level of FoxM1 in ten pairs of ESCC tissues and their adjacent nontumor tissues. High expression of FoxM1 mRNA was found in all of the ESCC cases. The expression of FoxM1 in nontumor tissues was arbitrarily set to 1. Each sample was repeated at least in duplicate

Fig. 4

High protein level of FoxM1 in ESCC cell lines. Immunoblot was performed to examine the protein level of FoxM1 in ESCC cell lines (HKESC-1/HK-1, HKESC-2/HK-2, HKESC-3/HK-3, HKESC-4/HK-4, and SLMT-1) and non-neoplastic esophageal cell line NE-1. High protein level of FoxM1 was associated with most ESCC cell lines, except HK-3

Fig. 5

Cytoplasmic localization of FoxM1 in ESCC tissues. Immunohistochemistry was used to study the expression and localization of FoxM1 in ESCC tissues and most cases of ESCC tissues had cytoplasmic staining of FoxM1. Original magnification, 200×

Fig. 6

Nuclear localization of FoxM1 in ESCC tissues. Immunohistochemistry was used to reveal the expression and localization of FoxM1 in ESCC tissues and about 25% of ESCC cases had tumors with nuclear FoxM1. Original magnification, 200×

Fig. 7

Localization of FoxM1 in nontumor tissues of ESCC patients. Immunohistochemistry was used to examine the expression and localization of FoxM1 in nontumor tissues from ESCC patients, which showed cytoplasmic FoxM1 expression in the proliferating layer. Original magnification, 200×

Fig. 8

Kaplan-Meier survival curves for cytoplasmic FoxM1. Kaplan-Meier survival curves were constructed for patients having high (n = 27) or low (n = 37) expression of cytoplasmic FoxM1. Log-rank test, P = 0.977

Fig. 9

Kaplan-Meier survival curves for nuclear FoxM1. Kaplan-Meier survival curves were generated for patients based on the presence (n = 16) or absence (n = 48) of nuclear FoxM1. Log-rank test, P = 0.697