Carcinogen-induced tumors in SFN-transgenic mice harbor a characteristic mutation spectrum of human lung adenocarcinoma

Keratinocyte growth factor in focus: A comprehensive review from structural and functional aspects to therapeutic applications of palifermin

Palifermin (Kepivance™) is the first therapeutic approved by the Food and Drug Administration for preventing and managing the oral mucositis provoked by myelotoxic and mucotoxic therapies. Palifermin is a recombinant protein generated from human keratinocyte growth factor (KGF) and imitates the function of endogenous KGF. KGF is an epithelial mitogen involved in various biological processes which belongs to the FGF family. KGF possesses a high level of receptor specificity and plays an important role in tissue repair and maintaining of the mucosal barrier integrity. Based on these unique features, palifermin was developed to enhance the growth of damaged epithelial tissues. Administration of palifermin has shown success in the reduction of toxicities of chemotherapy and radiotherapy, and improvement of the patient's quality of life. Notwithstanding all merits, the clinical application of palifermin is limited owing to its instability and production challenges. Hence, a growing number of ongoing researches are designed to deal with these problems and enhance the physicochemical and pharmaceutical properties of palifermin. In the current review, we discuss KGF structure and function, potential therapeutic applications of palifermin, as well as the latest progress in the production of recombinant human KGF and its challenges ahead.

Oxysterols Modify NLRP2 in Epithelial Cells, Identifying a Mediator of Ozone-induced Inflammation

Ozone (O3) is a prevalent air pollutant causing lung inflammation. Previous studies demonstrate that O3 oxidizes lipids, such as cholesterol, in the airway to produce oxysterols, such as secosterol A (SecoA), which are electrophiles that are capable of forming covalent linkages preferentially with lysine residues and that consequently modify protein function. The breadth of proteins modified by this oxysterol as well as the biological consequences in the lung are unknown. By using an alkynyl-tagged form of SecoA and shotgun proteomics, we identified 135 proteins as being modified in bronchial epithelial cells. Among them was NLRP2 (NLR family pyrin domain-containing protein 2), which forms an alkynyl-tagged SecoA-protein adduct at lysine residue 1019 (K1019) in the terminal leucine-rich repeat region, a known regulatory region for NLR proteins. NLRP2 expression in airway epithelial cells was characterized, and CRISPR-Cas9 knockout (KO) and shRNA knockdown of NLRP2 were used to determine its function in O3-induced inflammation. No evidence for NLPR2 inflammasome formation or an NLRP2-dependent increase in caspase-1 activity in response to O3 was observed. O3-induced proinflammatory gene expression for CXCL2 and CXCL8/IL8 was further enhanced in NLRP2-KO cells, suggesting a negative regulatory role. Reconstitution of NLRP2-KO cells with the NLRP2 K1019 mutated to arginine partially blocked SecoA adduction and enhanced O3-induced IL-8 release as compared with wild-type NLRP2. Together, our findings uncover NLRP2 as a highly abundant, key component of proinflammatory signaling pathways in airway epithelial cells and as a novel mediator of O3-induced inflammation.

Significance of stratifin in early progression of lung adenocarcinoma and its potential therapeutic relevance

Lung cancer is the most common cause of global cancer-related mortality, and the main histological type is adenocarcinoma, accounting for 50% of non-small cell lung cancer. In 2015, the World Health Organization (WHO) histological classification defined the concepts of "adenocarcinoma in situ" (AIS) and "minimally invasive adenocarcinoma" (MIA), which are considered to be adenocarcinomas at a very early stage. Although AIS and MIA have a very favorable outcome, once they progress to early but invasive adenocarcinoma (eIA), they can sometimes have a fatal outcome. We previously compared the expression profiles of eIA and AIS, and identified stratifin (SFN; 14-3-3 sigma) as a protein showing significantly higher expression in eIA than in AIS. Expression of SFN is controlled epigenetically by DNA demethylation, and its overexpression is significantly correlated with poorer outcome. In vitro and in vivo analyses have shown that SFN facilitates early progression of adenocarcinoma by enhancing cell proliferation. This review summarizes genetic and epigenetic abnormalities that can occur in early-stage lung adenocarcinoma and introduces recent findings regarding the biological significance of SFN overexpression during the course of lung adenocarcinoma progression. Therapeutic strategies for targeting SFN are also discussed.

Carcinogen-induced tumors in SFN-transgenic mice harbor a characteristic mutation spectrum of human lung adenocarcinoma

The landscape of genetic alterations in disease models such as transgenic mice or mice with carcinogen‐induced tumors has provided a huge amount of information that has shed light on the process of tumorigenesis in human non‐small‐cell lung cancer (NSCLC). We have previously identified stratifin (SFN) as a potent oncogene, and generated SFN‐transgenic (Tg‐SPC‐SFN^+/−) mice, which express human SFN (hSFN) only in the lung. Here, we have found that carcinogen nicotine‐derived nitrosaminoketone (NNK)‐induced tumors developing in Tg‐SPC‐SFN^+/− mice show a similar histology to human lung adenocarcinoma and exhibit high hSFN expression. In order to compare the genetic characteristics of Tg‐SPC‐SFN^+/− tumors and human lung adenocarcinoma, the former were subjected to whole‐exome sequencing. Interestingly, Tg‐SPC‐SFN^+/− tumors showed the distinct distribution of exonic mutations and high number of mutated genes and transversion. Moreover, Tg‐SPC‐SFN^+/− tumors showed 73 genes that were commonly detected in more than 2 tumors, mutations of which were also found in human lung adenocarcinoma. The expression levels of some of these genes were significantly associated with the clinical outcome of lung adenocarcinoma patients. Additionally, mutated genes in Tg‐SPC‐SFN^+/− tumors were closely associated with key canonical pathways such as PI3K/AKT signaling and apoptosis signaling. These results suggest that SFN overexpression is a universal abnormality in human lung adenocarcinogenesis and Tg‐SPC‐SFN^+/− tumors recapitulate key features of major human lung adenocarcinoma. Therefore, Tg‐SPC‐SFN^+/− mice provide a useful model for clarifying the molecular mechanism underlying lung adenocarcinogenesis.