The 3'-flap endonuclease XPF-ERCC1 promotes alternative end joining and chromosomal translocation during B cell class switching.

Robust alternative end joining (A-EJ) in classical non-homologous end joining (c-NHEJ)-deficient murine cells features double-strand break (DSB) end resection and microhomology (MH) usage and promotes chromosomal translocation. The activities responsible for removing 3' single-strand overhangs following resection and MH annealing in A-EJ remain unclear. We show that, during class switch recombination (CSR) in mature mouse B cells, the structure-specific endonuclease complex XPF-ERCC1SLX4, although not required for normal CSR, represents a nucleotide-excision-repair-independent 3' flap removal activity for A-EJ-mediated CSR. B cells deficient in DNA ligase 4 and XPF-ERCC1 exhibit further impaired class switching, reducing joining to the resected S region DSBs without altering the MH pattern in S-S junctions. In ERCC1-deficient A-EJ cells, 3' single-stranded DNA (ssDNA) flaps that are generated predominantly in S/G2 phase of the cell cycle are susceptible to nuclease resolution. Moreover, ERCC1 promotes c-myc-IgH translocation in Lig4-/- cells. Our study reveals an important role of the flap endonuclease XPF-ERCC1 in A-EJ and oncogenic translocation in mouse B cells.

Diagnostic value of endoscopic ultrasound elastography for benign and malignant digestive system tumors.

OBJECTIVE: To investigate the effect of endoscopic ultrasound real-time tissue elastography in differential diagnosis of benign and malignant digestive system tumors. METHODS: Forty-two patients with solid tumors of digestive system who were admitted to our hospital between October 2017 and October 2018 were selected. All patients were diagnosed by endoscopic ultrasound real-time tissue elastography. Elastography score was used. The strain ratios (SR) of the lesion and the surrounding control tissues were measured and compared. RESULTS: Lesions with elastography score no more than two points were evaluated as benign, while lesions with elastography score no less than three points were evaluated as malignant. The difference of the elastography score between the benign lesion group and malignant lesion group was statistically significant (P<0.05). The sensitivity, specificity and accuracy of endoscopic ultrasound elastography in the diagnosis of malignant tumors of digestive system were 91.4%, 88.9% and 87.5%, respectively. The SR of the benign lesions ranged from 0.01 to 7.34, with a median SR of 7.33; the SR of the malignant lesions ranged from 1.01 to 47.66, with a median SR of 20.07. The SR of the benign lesions was significantly lower than that of the malignant lesions (P<0.05). CONCLUSION: Elastography of benign and malignant tissues of digestive tract tumors has different image characteristics. Endoscopic ultrasound real-time tissue elastography is effective in differential diagnosis of digestive tract tumors as it can effectively determine whether a tumor is benign or malignant and improve diagnostic accuracy.

TES functions as a Mena-dependent tumor suppressor in gastric cancer carcinogenesis and metastasis.

BACKGROUND: In our previous study, we identified a candidate tumor suppressor gene, testin LIM domain protein (TES), in primary gastric cancer (GC). TES contains three LIM domains, which are specific interacting regions for the cell adhesion and cytoskeleton regulatory proteins. Mena is a known cytoskeleton regulator that regulates the assembly of actin filaments and modulates cell adhesion and motility by interacting with Lamellipodin (Lpd). Therefore, we hypothesized that TES plays a role as tumor suppressor in GC through interacting with Mena. This study aimed to investigate the tumor suppressive functions of TES in GC. METHODS: We explored the tumor suppressive effect of TES in GC by in vitro cell proliferation assay, colony formation assay, cell cycle analysis, Transwell assays, and in vivo tumorigenicity and metastasis assays. The interaction of TES and Mena was investigated through immunoprecipitation-based mass spectrometry. We also analyzed the expression of TES and Mena in 172 GC specimens using immunohistochemistry and investigated the clinicopathological and prognostic significance of TES and Mena in GC. RESULTS: TES suppressed GC cell proliferation and colony formation, induced cell cycle arrest, and inhibited tumorigenicity in vitro. Additionally, it inhibited GC cell migration and invasion in vitro and suppressed metastasis in vivo. TES interacted with Mena, and inhibited the interaction of Mena with Lpd. Transwell assays suggested that TES suppressed migration and invasion of GC cells in a Mena-dependent fashion. In GC patients with high Mena expression, the expression of TES was associated with tumor infiltration (P = 0.005), lymph node metastasis (P = 0.003), TNM stage (P = 0.003), and prognosis (P = 0.010). However, no significant association was observed in GC patients with low Mena expression. CONCLUSIONS: We believe that TES functions as a Mena-dependent tumor suppressor. TES represents a valuable prognostic marker and potential target for GC treatment.

SPLUNC1 knockout enhances LPS-induced lung injury by increasing recruitment of CD11b+Gr-1+ cells to the spleen of mice.

Short palate, lung and nasal epithelium clone 1 (SPLUNC1) is a tissue-specific gene of nasopharyngeal tissue, and has been recognized as a potential tumor-suppressor gene in nasopharyngeal carcinoma. As a secreted protein, SPLUNC1 plays an important role in innate immunity including antimicrobial and host defense. However, the related immune cells which are regulated by SPLUNC1 remain elusive. In the present study, an acute lung injury (ALI) mouse model was established by administration of lipopolysaccharide (LPS) intraperitoneal injections to wild-type and SPLUNC1-/- mice (5 mg/kg). Pathologic results showed that the SPLUNC1-/- group appeared to have more severe pulmonary damage and infiltrated inflammatory cells compared with the WT group after LPS treatment for 24, 48, 72 and 96 h. The mRNA expression levels of interleukin-6 (IL-6), chemokine (C-C motif) ligand-2 (CCL-2), chemokine (C-C motif) ligand-3 (CCL-3) and chemokine (C-X-C motif) ligand-1 (CXCL-1) in lungs of the SPLUNC1-/- group were higher than these levels in lungs of the WT group at different time points after LPS injection. The percentage of splenic CD11b+Gr-1+ myeloid-derived suppressor cells (MDSCs) in the SPLUNC1-/- mice was higher than this percentage in the WT mice at the time points of 72 and 96 h post LPS injection (P<0.05). These findings demonstrated that SPLUNC1 had a certain protective effect on the LPS-induced ALI mouse model as well as it was found to inhibit the recruitment of MDSCs to the spleen in this model.

CD38 enhances the proliferation and inhibits the apoptosis of cervical cancer cells by affecting the mitochondria functions.

Cervical cancer is one of the most common malignant tumors in women all over the world. The exact mechanism of occurrence and development of cervical cancer has not been fully elucidated. CD38 is a type II transmembrane glycoprotein, which was found to mediate diverse activities, including signal transduction, cell adhesion, and cyclic ADP-ribose synthesis. Here, we reported that CD38 promoted cell proliferation and inhibited cell apoptosis in cervical cancer cells by affecting the mitochondria functions. We established stable cervical cancer cell lines with CD38 over-expressed. CCK8 assay and colony formation assay indicated that CD38 promoted cervical cancer cell proliferation. Nude mouse tumorigenicity assay showed that CD38 significantly promotes tumor growth in vivo. CD38 also induced S phase accumulation in cell cycle analysis and suppressed cell apoptosis in cervical cancer cells. Meanwhile, flow cytometry analysis of mitochondria functions suggested that CD38 decreased intracellular Ca2+ levels in cervical cancer cells and CD38 was involved in down-regulation of ROS levels and prevented mitochondrial apoptosis in cervical cancer cells. The percentage of cells with loss of mitochondrial membrane potential (Δψm) in CD38-overexpressed cervical cancer cells was less than control groups. Furthermore, we found an up-regulation of MDM2, cyclinA1, CDK4, cyclinD1, NF-kB P65, c-rel, and a downregulation of P53, P21, and P38 by Western blot analysis. These results indicated that CD38 enhanced the proliferation and inhibited the apoptosis of cervical cancer cells by affecting the mitochondria functions.

CD38 is a putative functional marker for side population cells in human nasopharyngeal carcinoma cell lines.

Cancer stem cells (CSCs) are thought to be responsible for cancer progression and therapeutic resistance but identification of this subpopulation requires selective markers. Fortunately, side population (SP) cells analysis brings a novel method to CSCs study. In this study, we identified SP cells, which are demonstrated rich in CSCs, in four nasopharyngeal carcinoma (NPC) cell lines. We investigated SP cells from HK-1 NPC cell line and showed CSCs characteristics in this subpopulation. SP cells displayed greater proliferation and invasion and expressed high levels of CSCs markers than NSP cells. Furthermore, our microRNA microarray analysis of SP versus NSP cells revealed that CD38-related miRNAs were down-regulated in SP cell, but the mRNA and protein level of CD38 were highly expressed in SP cells. We further searched for molecules interacting with CD38 and identified ZAP70, which was also well expressed in SP cells at both mRNA and protein levels. Our results uncover a CD38 pathway that may regulate the proliferation and migration of SP cells from HK-1 NPC cell line.

CD24 promotes the proliferation and inhibits the apoptosis of cervical cancer cells in vitro.

The protein CD24 is a cell surface protein that appears to function as an adhesion molecule; its expression has been shown to correlate with prognosis in a variety of tumors. Herein, we investigated the possible role and mechanism of CD24 in cervical cancer. Our results showed that CD24 was overexpressed in cervical cancer tissues compared with that in the adjacent non­cancerous tissues by qPCR, immunohistochemistry and western blotting technologies. To explore the possible mechanism of CD24 in cervical cancer, we elucidated the effect of CD24 on the proliferation and apoptosis of cervical cancer HeLa cells and found that a considerable increase in cell proliferation was observed in the HeLa cells with CD24 overexpession. The rate of cell apoptosis was decreased in the HeLa/CD24 cells compared with the HeLa or HeLa/vector cells. Cell apoptosis is closely related with a reduction in mitochondrial membrane potential (ΔΨm) and an increase in intracellular reactive oxygen species (ROS) and calcium ion (Ca2+) concentrations. Our results showed that overexpression of CD24 in the cervical cancer HeLa cells, led to an increase in ΔΨm and a decrease in intracellular ROS and Ca2+ concentrations. Furthermore, we found that CD24 was correlated with dysregulation of the MAPK signaling pathway in cervical cancer tissues in vitro. At the same time, we found that CD24 overexpression affected the expression of p38, JNK2 and c-Jun in vitro. In summary, our results suggest that CD24 is upregulated in cervical cancer tissues and plays its functions by affecting the MAPK signaling pathway in cervical cancer.

Fra-1 is upregulated in gastric cancer tissues and affects the PI3K/Akt and p53 signaling pathway in gastric cancer.

Gastric cancer is an aggressive disease that continues to have a daunting impact on global health. Fra-1 (FOSL1) plays important roles in oncogenesis in various malignancies. We investigated the expression of Fra-1 in gastric cancer (GC) tissues by qPCR, immunohistochemistry (IHC) and western blot technologies. The results showed that Fra-1 was overexpressed in gastric cancer tissues compared with the adjacent non­cancerous tissues. To explore the possible mechanism of Fra-1 in GC, we elucidated the effect of Fra-1 in the apoptosis and cell cycle of gastric cancer cells, AGS, and found that a considerable decrease in apoptotic cells and increase of S phase rate were observed for AGS cells with Fra-1 overexpession. We identified and confirmed that Fra-1 affected the expression level of CTTN and EZR in vitro through LC-MS/MS analyses and western blot technology. Furthermore, we found that Fra-1 was correlated with dysregulation PI3K/Akt and p53 signaling pathway in gastric cancer tissues in vitro. Moreover, we found that Fra-1 overexpression affected the expression of PI3K, Akt, MDM2 and p53 in vivo. In summary, our results suggest that Fra-1 is upregulated in gastric cancer tissues and plays its function by affecting the PI3K/Akt and p53 signaling pathway in gastric cancer.

Dysregulation of the PI3K/Akt signaling pathway affects cell cycle and apoptosis of side population cells in nasopharyngeal carcinoma.

Increasing evidence has suggested that certain types of cancer possess their own stem-like cells, and that one subset of these cells, termed the side population (SP), may have an important role in tumorigenesis and cancer therapy. However, the molecular mechanisms underlying the modulation of SP cells in nasopharyngeal carcinoma (NPC) have remained elusive. In the present study, it was hypothesized that dysregulation of the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/Akt signaling pathway may influence SP and non-SP (NSP) phenotype. SP cells from the HK-1 NPC cell line were identified, and cancer stem cell markers were found to be highly expressed in SP cells compared with that of NSP cells. Freshly sorted SP cells demonstrated a significant increase in the proportion of cells in G0/G1 phase, while the majority of NSP cells were in the proliferative phase. Following 48 h of culture subsequent to cell sorting, the differences in cell cycle distribution between the SP and NSP cells converged. In addition, the apoptotic ratio of NSP cells was higher than that of SP cells at 24 h following sorting, but had no significant differences 48 h following sorting. To elucidate the potential mechanism mediating the cell cycle and apoptosis in SP cells, the expression levels of key molecules in the PI3K/Akt signaling pathway were evaluated. PI3K and Akt were upregulated, while 14-3-3σ protein was downregulated in SP cells when freshly sorted (0 h). However, there was no significant difference in the expression of these molecules between SP and NSP cells following 48 h of culture. These results suggested that dysregulation of the PI3K/Akt signaling pathway may be associated with the cell cycle and apoptosis of SP cells in NPC. However, further investigation is required to elucidate the detailed mechanisms underlying these effects.

CD38 is highly expressed and affects the PI3K/Akt signaling pathway in cervical cancer.

Cervical cancer is the second most common cancer and the fifth most deadly malignancy in females worldwide, affecting 500,000 individuals each year. It is the leading cause of cancer mortality among women in developing countries. Dysregulated activation of genes, such as CD44, SOX9 and SKP2, plays a role in cervical cancer. CD38 is known to be involved in activities typical of cell surface receptors, such as signaling for activation and proliferation events and heterotypic cell adhesion. CD38 contributes to disease progression and relapse in certain tumors, such as acute myeloid and chronic lymphocytic leukemia. To the best of our knowledge, there is currently no report on the relationship between CD38 and cervical cancer. Using qPCR, immunohistochemistry, and western blot analysis, the expression levels of CD38 were investigated and found to be upregulated in cervical cancer. CD38 was correlated with dysregulation of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway in cervical cancer tissues in vitro. At the same time, CD38 overexpression affected the expression of PI3K, Akt, MDM2 and p53 in vivo. The results of the present study suggested that CD38 is highly expressed in cervical carcinoma tissues and play an important role in dysregulation of the PI3K/Akt signaling pathway.

[Side population cells and progress in cancer stem cell research].

In recent years, cancer stem cells have become a hotspot for global researchers. Cancer stem cell theory deems that cells with self-renewal and differentiation potential play a key role in tumor resistance and relapse. These cells are named cancer stem cells. At present, the sorting methods include the side population cell sorting technique, screening techniques based on cell surface special markers, tumor sphere cultures, label retaining cell, ALDEFLUOR assays and so on. Side population cells are a small part of cells with the capacity of efflux DNA fluorescent dye Hoechst 33342 and present a low staining intensity in flow cytometry plot. Side population cells are rich in cancer stem cells, and its sorting method has been considered simple and effective in cancer stem cell research.