Bufalin suppresses esophageal squamous cell carcinoma progression by activating the PIAS3/STAT3 signaling pathway.

Background: Esophageal cancer, especially esophageal squamous cell carcinoma (ESCC), is a common malignant tumor of the digestive tract. Bufalin is an effective anti-tumor compound. However, little is known about the regulatory mechanisms of Bufalin in ESCC. To investigate the effect and molecular mechanism of Bufalin on the proliferation, migration and invasion of ESCC cells will provide a more reliable basis for the application of Bufalin in clinical tumor therapy. Methods: First, the half-inhibitory concentration (IC50) of Bufalin was evaluated by Cell Counting Kit-8 (CCK-8) assays. In vitro, the effects of Bufalin on the proliferation of the ECA109 cells was measured using CCK-8 and 5-ethynyl-2'-deoxyuridine assays. Wound-healing and transwell assays were used to evaluate the effects of Bufalin on the migration and invasion of the ECA109 cells. Further, to determine the mechanisms underlying the Bufalin-mediated suppression of cell progression in ESCC, total RNA was extracted from negative control (NC) and Bufalin treated cells to perform RNA-sequencing (RNA-seq) to screen for abnormally expressed genes. In vivo, the ECA 109 cells were subcutaneously injected into BALB/c nude mice to determine the effects of Bufalin on tumor cell proliferation. The protein inhibitor of activated signal transducer and activator of transcription 3 (PIAS3), signal transducer and activator of transcription 3 (STAT3), and phosphorylated STAT3 (p-STAT3) protein expression levels in the ECA109 cells were detected by Western blot. Results: The CCK-8 assays showed that the IC50 of Bufalin was 200 nM. The proliferation, migration, and invasion ability of the ECA109 cells was significantly inhibited in the Bufalin group in a concentration-dependent manner. In vivo, the Xenograft tumor model showed that Bufalin decreased the tumor volume and weight of the subcutaneous tumors. The RNA-seq results showed that the expression of PIAS3 was upregulated in the Bufalin group. Additionally, down-regulation of PIAS3 decreased the inhibition of STAT3, thereby increasing p-STAT3 expression. Finally, PIAS3 knockdown reversed the inhibitory effects of Bufalin on the proliferation, migration, and invasion of the ECA109 cells. Conclusions: Bufalin may inhibit the proliferation, migration, and invasion of the ECA109 cells through the PIAS3/STAT3 signaling pathway.

Mini-patient-derived xenograft assay based on microfluidic technology promises to be an effective tool for screening individualized chemotherapy regimens for advanced non-small cell lung cancer.

Patient-derived xenograft (PDX) assay has been widely used in preclinical research in patients with multidrug-resistant lung cancer. One hundred patients with non-small cell lung cancer (NSCLC) were divided into MiniPDX group and conventional group, with 50 cases in each group. The MiniPDX assay was established by enriching high-purity tumor cells using microfluidic technology to detect the drug sensitivity of NSCLC cells. All patients underwent conventional computed tomography (CT) scans of lung and mediastinum at baseline and during follow-up. Kaplan-Meier method was used to compare the overall survival and progression-free survival of two groups. The sensitivity of the same drug in different tumor xenograft varied greatly. The overall survival, progression-free survival, and clinical benefit rate of patients in the MiniPDX-guided chemotherapy group were significantly longer than those in the conventional chemotherapy group. MiniPDX assay may be an effective tool for screening chemotherapy regimens in NSCLC patients.

Testis-specific serine/threonine protein kinase 4 (Tssk4) phosphorylates Odf2 at Ser-76.

As a member of the testis-specific serine/threonine protein kinase (TSSK) family, Tssk4 is exclusively expressed in the testis and plays an essential role in male fertility. We previously reported that Tssk4 can associate with and phosphorylate Odf2, but the phosphorylation site is still unknown. Here we confirm that the C-terminal region (amino acids 214-638) of Odf2 is required for association with Tssk4. Furthermore, to identify the site at which Tssk4 phosphorylates Odf2, we generated several Odf2 point mutants (Ser/Thr/Lys to Ala) and identified serine 76 of Odf2 as one of the phosphorylation sites. In vivo, phosphorylated Odf2 was evaluated in mouse sperm using a specific phospho-Ser-76 Odf2 antibody and LC-MS/MS. These findings are the first to demonstrate the phosphorylation site in Odf2 by Tssk4, providing essential clues regarding the function of Tssk4 in regulating sperm motility and/or structure and thus male fertility.

Phosphorylated testis-specific serine/threonine kinase 4 may phosphorylate Crem at Ser-117.

We aimed to investigate the internal existence status of testis-specific serine/threonine kinase 4 (Tssk4) and the interaction of Tssk4 and Cre-responsive element modulator (Crem). The internal existence status of Tssk4 in testis of mice was detected using western blotting and dephosphorylation method. The interaction of Tssk4 and Crem was analyzed by western blotting, immunohistochemistry, immunofluorescence, in vitro co-immunoprecipitation assays, and in vitro kinase assay. The results revealed that Tssk4 existed in testis both in phosphorylation and unphosphorylation status by a temporal manner with the development of testis. Immunofluorescence results showed that Tssk4 had identical distribution pattern with Crem in testis, which was utterly different to the localization of Cre-responsive element binding (Creb). In conclusion, our study demonstrated that phosphorylated Tssk4 might participate in testis genes expressions by phosphorylating Crem at Ser-117.

Testis specific serine/threonine protein kinase 4 (TSSK4) leads to cell apoptosis relying on its kinase activity.

Testis specific serine/threonine protein kinase 4 (TSSK4) belongs to the TSSK family, and its members play an important role in spermatogenesis and/or spermiogenesis. Mouse TSSK4 has been reported to be expressed exclusively in the testis and can maintain its kinase activity through autophosphorylation at Thr-197. However, its biological function remains poorly understood. Here we found that GFP-TSSK4-overexpressed HeLa cells showed apoptotic bodies, indicating TSSK4 can lead to apoptosis in vitro. Furthermore, TSSK4 induced apoptosis in different cell lines including HeLa, Cos-7 and H1299 tested by flow cytometry but not its kinase-dead mutant TSSK4-K54M. TSSK4 knockout mice showed increased testes weight and decreased apoptotic spermatogonia and spermatocytes at 21st day after birth tested by TUNEL technology. So TSSK4 was able to induce cell apoptosis in vitro depending on its kinase activity, which leads to abnormal testes weight and apoptosis, shedding light on its function in the process of spermatogenesis and/or spermiogenesis.

Tssk4 is essential for maintaining the structural integrity of sperm flagellum.

Tssk4 belongs to the Testis Specific Serine/threonine protein Kinase (TSSK) family, members of which play an important role in spermatogenesis and/or spermiogenesis. Several Tssk family proteins have extensively been studied. However, the exact function of Tssk4 remains unclear. A Tssk4 knockout mouse model was generated and the males were subfertile due to seriously decreased sperm motility. The ultrastructure of the Tssk4(-/-)sperm tail is disorganized at the midpiece-principal piece junction, leading to a severe bend in the sperm flagellum. One or more axonemal microtubule doublets are absent and the midpiece is fused with the principal piece. Furthermore, we identified the association between Tssk4 and Odf2, a prominent cytoskeletal protein of the outer dense fiber (ODF) in sperm flagellum. Tssk4 can change the phosphorylation state of Odf2 and conversely Odf2 potentiates the autophosphorylation activity of Tssk4. These findings reveal that Tssk4 is required for maintaining the structural integrity of sperm flagellum and male fertility.

Testis specific serine/threonine kinase 4 (Tssk4) maintains its kinase activity by phosphorylating itself at Thr-197.

The testis specific serine/threonine protein kinase family (Tssk) members play important roles in spermatogenesis and/or spermiogenesis. Similar to other Tssk family members, Tssk4 protein shows exclusive expression in testis, but its biochemical and biological functions are still largely unknown. In present work, we generate a polyclonal antibody which specifically recognizes Tssk4 but not the other three Tssk family members (Tssk1, Tssk2 and Tssk3). By using the qualified antibody, we show that Tssk4 protein is constantly expressed in testis from haploid round spermatids to morphological mature spermatozoa. Further experiments reveal that Tssk4 has autophosphorylation activity and self-association character in vitro. Importantly, we find that autophosphorylation of Tssk4 at Thr-197 in the T-loop region is essential to its kinase activity. Taken together, these findings suggest that autophosphorylation at Thr-197 plays a critical role in maintaining Tssk4 kinase activity, which might be involved in spermiogenesis.

Isolation and characterization of mouse testis specific serine/threonine kinase 5 possessing four alternatively spliced variants.

Phosphorylation on serine/threonine or tyrosine residues of target proteins is an essential and significant regulatory mechanism in signal transduction during many cellular and life processes, including spermatogenesis, oogenesis and fertilization. In the present work, we reported the isolation and characterization of mouse testis-specific serine/threonine kinase 5 (Tssk5), which contains four alternatively spliced variants including, Tssk5alpha, Tssk5beta, Tssk5gamma and Tssk5delta. Moreover, the locus of Tssk5 is on chromosome 14qC3 and the four variants had a similar high expression in the testis and the heart; however, had a low expression in other tissues, except for Tssk5alpha which also had comparably high expression in the spleen. Each variant of Tssk5 expression began in the testis 16 days after birth. Aside from TSSK5alpha, the other isoforms have an insertion of ten amino acid residues (RLTPSLSAAG) in region VIb (HRD domain) (His-Arg-Asp). Moreover, only TSSK5alpha exhibited kinase activity and consistently, a further Luciferase Reporter Assay demonstrated that TSSK5beta, TSSK5gamma and TSSK5delta cannot be stimulated at the CREB/CRE responsive pathway in cmparison to TSSK5alpha. These findings suggest that TSSK5beta, TSSK5gamma, TSSK5delta may be pseudokinases due to the insertion, which may damage the structure responsible for active kinase activity. Pull-down assay experiments indicated that TSSK5beta, TSSK5gamma and TSSK5delta can directly interact with TSSK5alpha. In summary, these four isoforms with similar expression patterns may be involved in spermatogenesis through a coordinative way in testis.