Original contributionReduced nuclear and ectopic cytoplasmic expression of lysyl oxidase–like 2 is associated with lymph node metastasis and poor prognosis in esophageal squamous cell carcinoma☆
Introduction
Esophageal squamous cell carcinoma (ESCC), the most common histopathologic form of esophageal cancer, is one of the most prevalent cancers worldwide and is the fourth leading cause of cancer deaths in China [1], [2]. It has a poor survival rate because ESCC frequently exhibits local invasion and metastasis when discovered [3]. Thus, it is important to establish biological markers for determining treatment.
Lysyl oxidase (LOX) was described initially as a cuproenzyme that catalyzes oxidative deamination of lysine residues in collagen and elastin and makes extracellular matrix stable and strong [4]. Besides LOX, 4 human isoenzymes of LOX-like protein (LOXL) have been described. The LOX family is present in a variety of human tissues including the placenta, heart, lung, kidney, and pancreas [5], [6], [7], [8], [9]. It is involved in growth and development, senescence, chemotaxis, and cell mobility [10]. Many studies focused mainly on their function in tumor formation and progression. In this regard, LOX, perhaps, had a contradictory effect. Both the catalytic activity of LOX and its messenger RNA (mRNA) expression were dramatically down-regulated in most cancer cells. However, many studies demonstrated that the amount of LOX mRNA is elevated in highly invasive cancer cells [11]. High expression of LOXL2 was detected in many tumor cell lines and found to correlate closely with tumor invasion and metastasis [12], [13], [14], [15]. Similarly, we found it to be increased in cholangiocarcinoma, where it could promote lymph node and distant metastasis [16], [17]. Also, LOXL4 was up-regulated in some tumor cells such as bladder cancer and relative-to-normal epithelial cells. It could promote tumor cell colony formation and invasion [18], [19]. Nevertheless, the function of LOXL1 and LOXL3 in cancer was largely unknown. Some experiments indicated that all of them were expressed in highly invasive/metastatic breast cancer cells but not in poorly invasive/metastatic ones [20].
The functions of the LOX family in ESCC were not known, so we examined each member's expression in ESCC and analyzed its clinical relevance. The aim was to evaluate the effect of LOX family proteins on ESCC and identify risk factors.
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Cell lines and culture
Human kidney 293T cells and human ESCC cell lines (SHEEC, EC18, EC109, EC171, EC8712, KYSE70, KYSE140, KYSE150, KYSE180, KYSE510, COLO-680N) were used. The KYSE and COLO-680N lines were cultured in RPMI 1640 medium (HYCLONE, Beijing, China). The EC cell lines were cultured in 199 medium (HYCLONE) and SHEEC in 45% Dulbecco modified Eagle medium/45% Ham Nutrient Mixture F12 (GIBCO, Grand Island, NY). All media were supplemented with 10% fetal bovine serum and antibiotics (penicillin 100 U/mL and
Expression of LOX family in ESCC cell lines
The expression of LOX family mRNA was investigated in 10 ESCC cell lines by quantitative RT-PCR. Compared with 293T cells, only LOXL2 mRNA had higher expression in half of all ESCC cell lines (5/10), whereas other members showed mainly low expression (Fig. 1).
Messenger RNA levels of LOX family in ESCC tissues
Each of the LOX family members' expression at the mRNA level was investigated in 83 pairs of ESCC tissues by quantitative RT-PCR. Greater mRNA expression compared with normal esophageal tissues was documented in 56 ESCC tissues (67%) for
Discussion
The LOX family members are extracellular enzymes that catalyze oxidative deamination of lysine residues. More and more reports have shown that LOX family proteins also can locate in the intracellular domain to exert many complicated biological functions. Nevertheless, the roles of LOX family members in cancer are not clear, and the function in ESCC, if any, is largely unknown. In our study, the LOX mRNA concentrations in ESCC tissues were significantly higher than in normal tissues except for
Supplementary data
The following is the Supplementary data to this article.
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2020, Pharmacology and TherapeuticsCitation Excerpt :Reduced nuclear expression of LOXL2 and elevated cytoplasmic expression of LOXL2 were detected in ESCC tissues (Li et al., 2012). Moreover, these two different conditions of LOXL2 expression contributed to a poor overall survival in ESCC patients and promoted lymphatic metastasis (Li et al., 2012). SET and MYND domain-containing protein 3 (SMYD3) enhanced the LOXL2 transcription, which facilitated the proliferation, migration and invasion of ESCC cells (Zhu et al., 2016).
Lysyl oxidase-like 2 promotes esophageal squamous cell carcinoma cell migration independent of catalytic activity
2020, International Journal of Biochemistry and Cell BiologyCitation Excerpt :LOXL2 is highly expressed in a variety of tumors, including breast (Kirschmann et al., 2002; Hollosi et al., 2009), colorectal (Fong et al., 2007), lung (Salvador et al., 2017), pancreatic (Rückert et al., 2010; Tanaka et al., 2018), and gastric cancers (Peng et al., 2009). Our previous studies investigated the clinical importance of LOXL2 in esophageal squamous cell carcinoma (ESCC) and showed that the clinical pathological features of LOXL2 protein in ESCC cells are remarkably correlated with tumor location, lymph node metastasis, and tumor stage (Li et al., 2012). LOXL2 is an inducer of lung and liver fibroses and promotes fibrosis in LOXL2-expressing tumors; these activities require the enzymatic activity of LOXL2 (Barry-Hamilton et al., 2010; Vadasz et al., 2005).
LOXL2 promotes oncogenic progression in alveolar rhabdomyosarcoma independently of its catalytic activity
2020, Cancer LettersCitation Excerpt :LOXL2 is a secreted protein that localizes in RMS cell nuclei and cytoplasm, as in multiple other cell types and tissues [8,25]. Due to its complex function and multiple localizations, different correlations between its subcellular distribution and its molecular function and aggressiveness have been established, such us increased cytoplasmic/perinuclear LOXL2 localization and poor prognosis and metastasis [26–28]. Remarkably, LOXL2 staining in tissues from ARMS xenografts or RMS patients is mainly cytoplasmic.
Dynamic matrisome: ECM remodeling factors licensing cancer progression and metastasis
2018, Biochimica et Biophysica Acta - Reviews on CancerCitation Excerpt :These modifications increase ECM stiffness and rigidity and through their ability to cross-link collagen, LOX family members are recognized to affect cancer metastasis [64,65]. High levels of LOX mRNA and protein are found in several malignancies [66] and correlate with reduced survival in patients in multiple cancer cohorts [64,67–71]. Elevated concentrations of intratumoral LOX proteins also correlated with adverse pathological features including tumor stage, grade, tumor invasion, and lymph node metastasis in various cancers [72,73].