Original contributionOverexpression and altered subcellular localization of autophagy-related 16-like 1 in human oral squamous-cell carcinoma: correlation with lymphovascular invasion and lymph-node metastasis☆
Introduction
Oral squamous cell carcinoma (OSCC) is a major cause of morbidity and mortality globally, accounting for 275000 new cases and more than 120000 deaths annually [1]. Despite therapeutic and diagnostic advances, patients are often diagnosed at advanced stages and mortality rates are still increasing [2]. This highlights the need for continued efforts to uncover suitable biomarkers for early disease diagnosis and to understand disease pathogenesis as a first step toward improving treatment. We recently developed a strategy of using proteomic technologies to search for significant molecular biomarker characteristics of oral carcinogenesis [3]. Among the proteins identified, autophagy-related 16-like 1 (ATG16L1) expression was found to be upregulated in OSCC-derived cell lines compared to human normal oral keratinocytes using a fluorescent 2-dimensional differential in-gel electrophoresis system and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.
ATG16L1, also known as Atg16 or Atg16L, is a member of the autophagy-related protein family, which has an essential role in autophagy. Autophagy mediates bulk degradation of the cytoplasmic component in lysosomes and vacuoles [4], and is implicated in numerous biologic processes, including the anti-aging mechanism [5], and in the survival response during nutrient depletion, or in the absence of growth factors, or both [6]. Autophagy involves formation of a double-membrane vesicle, which encapsulates cytoplasm and organelles and then fuses with lysosomes, thus degrading the vesicle contents [7]. The formation of the autophagosome depends on autophagy-related proteins [8].
The ATG16L1 gene was originally identified in yeast [9]. In mammalians, the mouse homologue of ATG16L1, Atg16L, was identified initially as a functional counterpart of yeast Atg16, which binds to the Atg12-Atg5 conjugate and forms a multimeric complex crucial to autophagosome formation [10]. Human ATG16L1 was first identified in human fetal brain cDNA library, which shows 93% similarity to mouse orthologue Atg16L [11]. A recent study showed that functional knockdown of the gene using RNA-silencing methods in a human HeLa cell line abrogates the autophagy of Salmonella typhimurium[12], suggesting that human ATG16L1 is also indispensable for autophagic function.
Although many recent publications have highlighted the role of autophagy in the regulation of cancer development and progression [13], [14], ATG16L1 has not been characterized previously in the human tumors including OSCC, for which nothing is known in the context of human carcinogenesis. The purpose of the current study was to determine ATG16L1 protein expression in a series of human primary OSCCs and oral premalignant lesions (OPLs) and correlate the expression with the clinical relevance in patients with OSCC.
Section snippets
Tissue specimens
Thirty-three pairs of typical keratinizing-type OSCC samples (not including verrucous or other variant types) and corresponding normal oral epithelium tissues were retrieved nonselectively from our hospital files and pathology database from 1999 to 2006. All patients (23 men, 10 women; mean age, 63.0+13.4 years; range, 27-83 years) provided informed consent according to the protocol that was reviewed and approved by the institutional review board of Chiba University before any procedures were
Expression and subcellular localization of ATG16l1 in OPLs and OSCCs
Immunohistochemical staining was performed using a series of OSCC specimens obtained intraoperatively, including 33 OSCCs with corresponding normal tissues and 31 OPLs that were diagnosed histopathologically as leukoplakia with epithelial dysplasia. Considering that evidence showed that the malignant transformation rate of oral leukoplakia with dysplasia was apparently higher than that of oral leukoplakia without dysplasia [18], patients with advanced OPLs, defined as leukoplakia exhibiting
Discussion
Of particular interest in the current results is that, although it is well known that most mammalian Atg16L is normally present in the cytoplasm as a complex with the Atg12-Atg5 conjugate [10], ATG16L1 protein subcellular distribution at a high expression level was observed in the cytoplasm and the plasma membrane of OSCC cells, whereas no or faint protein expression was detected in either compartment in normal oral epithelium cells. Furthermore, strong ATG16L1 immunoreaction was also
Acknowledgments
We thank Lynda C. Charters for editing this manuscript.
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Impact of lymphovascular invasion in oral squamous cell carcinoma: A meta-analysis
2021, Oral Surgery, Oral Medicine, Oral Pathology and Oral RadiologyCitation Excerpt :Among 36 included studies, 11 studies reported oral tongue SCC14-24 and 1 study each focused on floor of mouth cancer7 and buccal mucosa SCC.25 The tumor site of OSCC was mixed in the other 23 studies.26-48 With regard to the diagnostic modality for LVI, only 1 study used immunohistochemistry (IHC), 11 used hematoxylin and eosin (H&E) staining, and the other 24 did not mention the staining method for LVI.
High LC3 expression correlates with poor survival in patients with oral squamous cell carcinoma
2013, Human PathologyCitation Excerpt :The presence of autophagy in OSCC has been demonstrated, yet the role of autophagy is still matter of debate. Autophagy-related 16-like 1, a component of a large protein complex essential for autophagosome formation, has been shown to be overexpressed and correlated with lymphovascular invasion and lymph node metastasis in OSCC [23]. On the contrary, Beclin-1 has been reported in a study consisting of 10 OSCC cases to be down-regulated thus suggesting inhibition of the autophagic pathway in OSCC [24].
G15, a GPR30 antagonist, induces apoptosis and autophagy in human oral squamous carcinoma cells
2013, Chemico-Biological InteractionsCitation Excerpt :In the early stage, in contrast, autophagy inhibits tumor cell growth. Compared to human normal oral keratinocytes, the expression of autophagy-related 16-like 1 (ATG16L1) was found to be upregulated in OSCC-derived cell lines [30]. We found that G15 increased the expression of both LC3B-I and LC3B-II in SCC4 cells.
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This study was partly supported by a Grant-in-Aid Scientific Research (No. 16209059) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.