Sam68 regulates cell proliferation and cell adhesion-mediated drug resistance (CAM-DR) via the AKT pathway in non-Hodgkin's lymphoma

Coalescent RNA-localizing and transcriptional activities of SAM68 modulate adhesion and subendothelial basement membrane assembly

Endothelial cell interactions with their extracellular matrix are essential for vascular homeostasis and expansion. Large-scale proteomic analyses aimed at identifying components of integrin adhesion complexes have revealed the presence of several RNA binding proteins (RBPs) of which the functions at these sites remain poorly understood. Here, we explored the role of the RBP SAM68 (Src associated in mitosis, of 68 kDa) in endothelial cells. We found that SAM68 is transiently localized at the edge of spreading cells where it participates in membrane protrusive activity and the conversion of nascent adhesions to mechanically loaded focal adhesions by modulation of integrin signaling and local delivery of β-actin mRNA. Furthermore, SAM68 depletion impacts cell-matrix interactions and motility through induction of key matrix genes involved in vascular matrix assembly. In a 3D environment SAM68-dependent functions in both tip and stalk cells contribute to the process of sprouting angiogenesis. Altogether, our results identify the RBP SAM68 as a novel actor in the dynamic regulation of blood vessel networks.

Role of Sam68 in Sunitinib induced renal cell carcinoma apoptosis

Sunitinib is one of the first‐line targeted drugs for metastatic renal cell carcinoma (RCC) with dual effects of antiangiogensis and proapoptosis. Sam68 (Src‐associated in mitosis, 68 KDa), is found being involved in cell apoptosis. This article reveals that Sam68 impacts the sensitivity to sunitinib by mediating the apoptosis of RCC cells. Immunohistochemical staining indicated that the Sam68 expression levels in sunitinib sensitive tumor tissues were markedly higher than those in sunitinib resistant tumor tissues. Sunitinib induced RCC cell apoptosis in a concentration‐dependent manner and inhibited the expression of total and phosphorylated Sam68 (p‐Sam68). Downregulation of Sam68 expression inhibited RCC cell apoptosis induced by sunitinib. While upregulation of Sam68 expression could enhance apoptosis induced by sunitinib. Xenograft models showed that tumors in the Sam68‐knockdown group did not shrink as much as those in the control group after treatment with sunitinib for 4 weeks. Together, our results suggest that Sam68 expression is associated with the sensitivity of ccRCC patients to sunitinib. Sam68 may promote cell apoptosis induced by sunitinib, and the Sam68 expression level may be a biomarker for predicting sunitinib sensitivity in ccRCC patients.

Single-cell transcriptome analysis of diffuse large B cells in cerebrospinal fluid of central nervous system lymphoma

Diffuse large B cells in the cerebrospinal fluid (CSF-DLBCs) have offered great promise for the diagnostics and therapeutics of central nervous system lymphoma (CNSL) leptomeningeal involvement. To explore the phenotypic states of CSF-DLBCs, we analyzed the transcriptomes of more than one thousand CSF-DLBCs from six patients with CNSL diffuse large B-cell lymphoma (DLBCL) using Smart-seq2 single-cell RNA sequencing. CSF-DLBCs were defined based on abundant expression of B-cell markers, the active cell proliferation and energy metabolism properties, and immunoglobulin light chain restriction. We identified inherent heterogeneity of CSF-DLBCs, which were mainly manifested in cell cycle state, cancer-testis antigen expression, and classification based on single-cell germinal center B-cell signature. In addition, the 16 upregulated genes in CSF-DLBCs compared to various normal B cells showed great possibility in the homing effect of the CNS-DLBCL for the leptomeninges. Our results will provide insight into the mechanism research and diagnostic direction of CNSL-DLBCL leptomeningeal involvement.

CAM-DR: Mechanisms, Roles and Clinical Application in Tumors

Despite the continuous improvement of various therapeutic techniques, the overall prognosis of tumors has been significantly improved, but malignant tumors in the middle and advanced stages still cannot be completely cured. It is now evident that cell adhesion-mediated resistance (CAM-DR) limits the success of cancer therapies and is a great obstacle to overcome in the clinic. The interactions between tumor cells and extracellular matrix (ECM) molecules or adjacent cells may play a significant role in initiating the intracellular signaling pathways that are associated with cell proliferation, survival upon binding to their ligands. Recent studies illustrate that these adhesion-related factors may contribute to the survival of cancer cells after chemotherapeutic therapy, advantageous to resistant cells to proliferate and develop multiple mechanisms of drug resistance. In this review, we focus on the molecular basis of these interactions and the main signal transduction pathways that are involved in the enhancement of the cancer cells’ survival. Furthermore, therapies targeting interactions between cancer cells and their environment to enhance drug response or prevent the emergence of drug resistance will also be discussed.

Transcriptome-wide identification and competitive disruption of sacum-binding partners in human colorectal cancer

Human sacum is regulatory adaptor protein involved in cellular signaling network of colorectal cancer. Molecular evidences suggest that the protein is integrated into oncogenic signaling network by binding to SH3-containing proteins through its proline-rich motifs. In this study, we have performed a transcriptome-wide analysis and identification of sacum-binding partners in the genome profile of human colorectal cancer. The sacum-binding potency of SH3-containing proteins found in colorectal cancer was investigated by using bioinformatics modeling and intermolecular binding analysis. With the protocol we were able to predict those high-affinity domain binders of the proline-rich peptides of human sacum in a high-throughput manner, and to analyze sequence-specific interaction in the domain-peptide recognition at molecular level. Consequently, a number of putative domain binders with both high affinity and specificity were identified, from which the Src SH3 domain was selected as a case study and tested for its binding activity towards the sacum peptides. We also designed two peptide variants that may have potent capability to competitively disrupt sacum interaction with its partners.

Transcriptome-wide identification and competitive disruption of sacum-binding partners in human colorectal cancer

Human sacum is regulatory adaptor protein involved in cellular signaling network of colorectal cancer. Molecular evidence suggests that the protein is integrated into oncogenic signaling network by binding to SH3-containing proteins through its proline-rich motifs. In this study, we have performed a transcriptome-wide analysis and identification of sacum-binding partners in the genome profile of human colorectal cancer. The sacum-binding potency of SH3-containing proteins found in colorectal cancer was investigated by using bioinformatics modeling and intermolecular binding analysis. With the protocol we were able to predict those high-affinity domain binders of the proline-rich peptides of human sacum in a high-throughput manner, and to analyze sequence-specific interaction in the domain-peptide recognition at molecular level. Consequently, a number of putative domain binders with both high affinity and specificity were identified, from which the Src SH3 domain was selected as a case study and tested for its binding activity towards the sacum peptides. We also designed two peptide variants that may have potent capability to competitively disrupt sacum interaction with its partners.

DIXDC1 promotes tumor proliferation and cell adhesion mediated drug resistance (CAM-DR) via enhancing p-Akt in Non-Hodgkin's lymphomas

DIX domain containing 1 (DIXDC1), is a human homolog of Ccd1, a DIX domain containing protein in zebrafish. The present study was undertaken to determine the expression and biologic function of DIXDC1 in Non-Hodgkin's lymphoma (NHL). Clinically, we detected that the expression of DIXDC1 was significantly lower in the indolent lymphomas compared with the progressive lymphomas by immunohistochemistry analysis. Functionally, we found that DIXDC1 could promote cell proliferation via modulating cell cycle progression and PI3K/AKT signaling pathway in NHLs. Moreover, we confirmed that DIXDC1 was involved in the process of lymphoma cell adhesion mediated drug resistance (CAM-DR). Adhesion to fibronectin (FN) or HS-5 up-regulated DIXDC1 expression, and up-regulation of DIXDC1 resulted in an increased expression of p-AKT, which promoted CAM-DR. Our finding supports the role of DIXDC1 in cell proliferation, cell cycle and CAM-DR in NHLs. We propose that inhibition of DIXDC1 expression may be a novel therapeutic approach for NHLs patients, and it may be a target for drug resistance.

Knockdown of Tubulin Polymerization Promoting Protein Family Member 3 Suppresses Proliferation and Induces Apoptosis in Non-Small-Cell Lung Cancer

Our previous studies demonstrated that depletion of tubulin polymerization promoting protein family member 3 (TPPP3) inhibits proliferation and induces apoptosis of HeLa cells. However, the expression and roles of TPPP3 in cancers remain largely unknown. In this study, we investigated the expression of TPPP3 in clinicopathological correlations in non-small-cell lung cancer (NSCLC) samples by immunohistochemistry. TPPP3 expression was significantly upregulated in NSCLC tissues, and high TPPP3 expression was positively associated with tumor size, lymph node metastasis, clinical stage, and poor survival. Furthermore, knockdown of TPPP3 by shRNA significantly inhibited cell proliferation and induced cell apoptosis and cell cycle arrest in vitro. In addition, depletion of TPPP3 inhibited lung cancer growth in vivo in the xenografts of H1299 cells; this effect was accompanied by the suppression of Ki67 expression. Our data suggested that TPPP3 might act as an oncogene in NSCLC. TPPP3 warrants consideration as a therapeutic candidate with anti-tumor potential.