Suppressor of cytokine signaling 1 interacts with oncogenic lymphocyte-specific protein tyrosine kinase

Type I T cells sensitize treatment refractory tumors to chemotherapy through inhibition of oncogenic signaling pathways

BACKGROUND

The most common clinical outcome observed after treatment with immune checkpoint inhibitor antibodies is disease stabilization. Using vaccines to generate high levels of tumor antigen-specific T-helper 1 (Th1), we show that tumors not eradicated by vaccination demonstrate prolonged disease stabilization. We evaluated the mechanism by which type I T cells inhibit disease progression and potentially influence the subsequent clinical response to standard therapy in treatment refractory cancers.

METHODS

We employed a meta-analysis of studies with tumor growth from four different vaccines in two different mammary cancer models. The T-cell subtype and cytokine essential for vaccine-induced tumor inhibition was determined by in vivo neutralization studies and immunohistochemistry. The role of interferon gamma (IFN-γ) in receptor tyrosine kinase and downstream signaling was determined by immunoblotting. The role of suppressor of cytokine signaling 1 (SOCS1) on IFN-γ signaling was evaluated on SOCS1-silenced cells with immunoblotting and immunoprecipitation. The effect of vaccination on growth factor receptor signaling pathways, performed in both luminal (TgMMTVneu) and basal (C3(1)-Tag) mammary cancer models treated with paclitaxel or an anti-HER2-neu monoclonal antibody were assessed via immunoblotting.

RESULTS

Immunization with an epitope-based vaccine targeting a representative tumor antigen resulted in elevated tumor trafficking Tbet+CD4 T cells, decreased tumor proliferation and increased apoptosis compared with control vaccinated mice. The resulting disease stabilization was dependent on IFN-γ-secreting CD4+ T cells. In the presence of excess IFN-γ, SOCS1 became upregulated in tumor cells, bound insulin receptor, insulin like growth factor receptor 1 and epidermal growth factor receptor resulting in profound oncogenic signaling inhibition. Silencing SOCS1 restored growth factor receptor signaling and proliferation and prevented cell death. Similar signaling perturbations were detected in vaccinated mice developing antigen-specific Th1 cells. Vaccination synergized with standard therapies and restored disease sensitivity to treatment with both a neu-specific antibody and paclitaxel in TgMMTVneu and to paclitaxel in C3(1)-Tag. Combination of vaccination and chemotherapy or biological therapy was more effective than monotherapy alone in either model and resulted in complete resolution of disease in some individuals.

CONCLUSIONS

These data suggest the clinical activity of type I T cells extends beyond direct tumor killing and immune therapies designed to increase type I T cells and could be integrated into standard chemotherapy regimens to enhance therapeutic efficacy.

UBE2O Promotes Progression and Epithelial-Mesenchymal Transition in Head and Neck Squamous Cell Carcinoma

Background

UBE2O, as a member of the ubiquitin-conjugating enzyme family, is abnormally expressed and exhibits abnormal functions in human malignancies. However, the function of UBE2O in head and neck squamous cell carcinoma (HNSCC) remains unknown. Therefore, our study aims to investigate the role of UBE2O in HNSCC progression and the underlying mechanisms.

Methods

The expression of UBE2O in HNSCC patients was investigated with data from the Cancer Genome Atlas (TCGA) and from a separate primary tumor cohort. The function of UBE2O in HNSCC cells was studied by cell viability assay, colony formation assay, wound healing assay, and cell migration and invasion chamber assay. The effect of UBE2O on tumor growth in vivo was determined in a subcutaneous xenograft model of HNSCC.

Results

TCGA data showed that UBE2O mRNA expression was dramatically increased in HNSCC tissues and that patients with high expression of UBE2O transcripts had a worse survival prognosis than patients with low expression of UBE2O transcripts. Gain-of-function and loss-of-function analyses revealed that oncogenic UBE2O enhanced the proliferation, migration and invasion of HNSCC cells in vitro. Further, mechanistic analysis revealed that UBE2O induced the epithelial-mesenchymal transition (EMT) phenotype and also potentiated TGF-β1-induced EMT, and thus leading to an enhanced capacity of migration and invasion in HNSCC. Finally, xenograft models showed that UBE2O knockout obviously inhibited the occurrence of EMT, angiogenesis and tumor growth in HNSCC in vivo.

Conclusion

Our study indicates that UBE2O acts as an oncogene to promote the malignant progression and EMT of HNSCC.

A proteomics outlook towards the elucidation of epithelial-mesenchymal transition molecular events

The main cause of death in cancer is the spread, or metastasis, of cancer cells to distant organs with consequent tumor formation. Additionally, metastasis is a process that demands special attention, as the cellular transformations make cancer at this stage very difficult or occasionally even impossible to be cured. The main process that converts epithelial tumor cells to mesenchymal-like metastatic cells is the Epithelial to Mesenchymal Transition (EMT). This process allows stationary and polarized epithelial cells, which are connected laterally to several types of junctions as well as the basement membrane, to undergo multiple biochemical changes that enable disruption of cell-cell adherence and apical-basal polarity. Moreover, the cells undergo important reprogramming to remodel the cytoskeleton and acquire mesenchymal characteristics such as enhanced migratory capacity, invasiveness, elevated resistance to apoptosis and a large increase in the production of ECM components. As expected, the alterations of the protein complement are extensive and complex, and thus exploring this by proteomic approaches is of particular interest. Here we review the overall findings of proteome modifications during EMT, mainly focusing on molecular signatures observed in multiple proteomic studies as well as coordinated pathways, cellular processes and their clinical relevance for altered proteins. As a result, an interesting set of proteins is highlighted as potential targets to be further investigated in the context of EMT, metastasis and cancer progression.

Effect of tumor microenvironment on pathogenesis of the head and neck squamous cell carcinoma: a systematic review

The tumor microenvironment (TME) is comprised of many different cell populations, such as cancer-associated fibroblasts and various infiltrating immune cells, and non-cell components of extracellular matrix. These crucial parts of the surrounding stroma can function as both positive and negative regulators of all hallmarks of cancer development, including evasion of apoptosis, induction of angiogenesis, deregulation of the energy metabolism, resistance to the immune detection and destruction, and activation of invasion and metastasis. This review represents a summary of recent studies focusing on describing these effects of microenvironment on initiation and progression of the head and neck squamous cell carcinoma, focusing on oral squamous cell carcinoma, since it is becoming clear that an investigation of differences in stromal composition of the head and neck squamous cell carcinoma microenvironment and their impact on cancer development and progression may help better understand the mechanisms behind different responses to therapy and help define possible targets for clinical intervention.

Nuclear lymphocyte-specific protein tyrosine kinase and its interaction with CR6-interacting factor 1 promote the survival of human leukemic T cells

Overexpression and hyperactivation of lymphocyte-specific protein tyrosine kinase (Lck) have been associated with leukemia development. We previously showed that, other than its known function as a cytoplasmic signal transducer, Lck also acts as a nuclear transcription factor in mouse leukemic cells. In the present study, we demonstrated the presence of nuclear Lck in human leukemic T cells and in primary cells. We further established a positive correlation between Lck nuclear localization and its kinase activity. Proteomic analysis identified CR6-interacting factor 1 (CRIF1) as one of the Lck-interacting proteins. CRIF1 and Lck association in the nucleus was confirmed both by immunofluorescence microscopy and co-immunoprecipitation in human leukemic T cells. Close-range interaction between Lck and CRIF1 was validated by in situ proximity ligation assay (PLA). Consistent with the role of nuclear CRIF1 as a tumor suppressor, CRIF1 silencing promotes leukemic T cell survival in the absence of growth factors. This protective effect can be recapitulated by endogenous Lck or reconstituted Lck in leukemic T cells. All together, our results support a novel function of nuclear Lck in promoting human leukemic T cell survival through interaction with a tumor suppressor. It has important implications in defining a paradigm shift of non-canonical protein tyrosine kinase signaling.

Low expression of SOCS-1 and SOCS-3 is a poor prognostic indicator for gastric cancer patients

BACKGROUND AND OBJECTIVES

Inflammation plays an important role in gastric cancer (GC) development and progression. Suppressor of cytokine signaling (SOCS)-1 and SOCS-3 negatively regulate proinflammatory cytokine signaling; however, their prognostic significance in GC remains unknown. We evaluated the clinicopathological correlation and prognostic significance of SOCS-1 and SOCS-3 in GC.

METHODS

SOCS-1 and SOCS-3 mRNA levels were analyzed in 80 paired gastric tumor and adjacent normal mucosal tissues using a microarray dataset from the Gene Expression Omnibus. Univariate and multivariate analyses were performed to investigate the prognostic impact of SOCS-1 and SOCS-3 immunohistochemical expression on overall survival (OS) and relapse-free survival (RFS) in 186 consecutive GC patients who underwent curative surgery.

RESULTS

SOCS-1 and SOCS-3 mRNA expression levels were lower in gastric tumor tissues than in matched normal mucosa. OS and RFS were significantly longer in the high SOCS-1 and SOCS-3 expression groups than in their corresponding low expression groups (p < 0.05). High simultaneous SOCS-1 and SOCS-3 expression were associated with longer OS compared with low simultaneous SOCS-1 and SOCS-3 expression (68.8 vs. 22.2 months; p < 0.001). SOCS-1 [hazards ratio (HR) 0.54, 95 % confidence interval (CI) 0.33-0.87, p = 0.011] and SOCS-3 (HR 0.46, 95 % CI 0.26-0.80, p = 0.006) were independent prognostic factors for OS. Only SOCS-1 (HR 0.20, 95 % CI 0.11-0.38, p = 0.006) was an independent prognostic factor for RFS.

CONCLUSION

Low SOCS-1 and SOCS-3 expression are poor prognostic indicators in GC. GC patients with low SOCS-1 and SOCS-3 expression need close follow-up.

Protein degradation machinery is present broadly during early development in the sea urchin

Ubiquitin-dependent proteosome-mediated proteolysis is an important pathway of degradation that controls the timed destruction of cellular proteins in all tissues. All intracellular proteins and many extracellular proteins are continually being hydrolyzed to their constituent amino acids as a result of their recognition by E3 ligases for specific targeting of ubiquitination. Gustavus is a member of an ECS-type E3 ligase which interacts with Vasa, a DEAD-box RNA helicase, to regulate its localization during sea urchin embryonic development, and Gustavus mRNA accumulation is highly localized and dynamic during development. We tested if the core complex for Gustavus function was present in the embryo and if other SOCS box proteins also had restricted expression profiles that would inform future research. Expression patterns of the key members of the proteasomal function, such as the E3 core complex which interacts with Gustavus, and other E3-SOCS box proteins, are widely spread and dynamic in early development of the embryo suggesting broad core complex availability in the proteasome degradation pathway and temporal/spatial enrichments of various E3 ligase dependent targeting mechanisms.

Engagement of T-cell antigen receptor and CD4/CD8 co-receptors induces prolonged STAT activation through autocrine/paracrine stimulation in human primary T cells

Signal transducer and activator of transcription (STAT) proteins are key signaling molecules in response to cytokines and in regulating T cell biology. However, there are contradicting reports on whether STAT is involved in T-cell antigen receptor (TCR) signaling. To better define the role of STAT in TCR signaling, we activated the CD4/CD8-associated Lck kinase by co-crosslinking TCR and CD4/CD8 co-receptors in human peripheral blood T cells. Sequential STAT1, STAT3 and STAT5 activation was observed 1 h after TCR stimulation suggesting that STAT proteins are not the immediate targets in the TCR complex. We further identified interferon-γ as the key cytokine in STAT1 activation upon TCR engagement. In contrast to transient STAT activation in cytokine response, this autocrine/paracrine-induced STAT activation was sustained. It correlated with the absence of two suppressors of cytokine signaling (SOCS) proteins, SOCS3 and cytokine-inducible SH2 containing protein that are negative feedback regulators of STAT signaling. Moreover, enforced expression of SOCS3 inhibited tyrosine phosphorylation of zeta-associated protein kinase of 70 kD in TCR-stimulated human Jurkat T cells. This is the first report demonstrating delayed and prolonged STAT activation coordinated with the loss of SOCS expression in human primary T cells after co-crosslinking of TCR and CD4/CD8 co-receptors.

Nuclear localization of lymphocyte-specific protein tyrosine kinase (Lck) and its role in regulating LIM domain only 2 (Lmo2) gene

LIM domain only protein 2 (Lmo2) is a transcription factor that plays a critical role in the development of T-acute lymphoblastic leukemia (T-ALL). A previous report established a link between Lmo2 expression and the nuclear presence of oncogenic Janus kinase 2 (JAK2), a non-receptor protein tyrosine kinase. The oncogenic JAK2 kinase phosphorylates histone H3 on Tyr 41 that leads to the relief of Lmo2 promoter repression and subsequent gene expression. Similar to JAK2, constitutive activation of lymphocyte-specific protein tyrosine kinase (Lck) has been implicated in lymphoid malignancies. However, it is not known whether oncogenic Lck regulates Lmo2 expression through a similar mechanism. We show here that Lmo2 expression is significantly elevated in T cell leukemia LSTRA overexpressing active Lck kinase and in HEK 293 cells expressing oncogenic Y505FLck kinase. Nuclear localization of active Lck kinase was confirmed in both Lck-transformed cells by subcellular fractionation and immunofluorescence microscopy. More importantly, in contrast to oncogenic JAK2, oncogenic Lck kinase does not result in significant increase in histone H3 phosphorylation on Tyr 41. Instead, chromatin immunoprecipitation experiment shows that oncogenic Y505FLck kinase binds to the Lmo2 promoter in vivo. This result raises the possibility that oncogenic Lck may activate Lmo2 promoter through direct interaction.

Nuclear localization of pyruvate dehydrogenase complex-E2 (PDC-E2), a mitochondrial enzyme, and its role in signal transducer and activator of transcription 5 (STAT5)-dependent gene transcription

STAT (signal transducer and activator of transcription) proteins play a critical role in cellular response to a wide variety of cytokines and growth factors by regulating specific nuclear genes. STAT-dependent gene transcription can be finely tuned through the association with co-factors in the nucleus. We showed previously that STAT5 (including 5a and 5b) specifically interacts with a mitochondrial enzyme PDC-E2 (E2 subunit of pyruvate dehydrogenase complex) in both leukemic T cells and cytokine-stimulated cells. However, the functional significance of this novel association remains largely unknown. Here we report that PDC-E2 may function as a co-activator in STAT5-dependent nuclear gene expression. Subcellular fractionation analysis revealed that a substantial amount of PDC-E2 was constitutively present in the nucleus of BaF3, an interleukin-3 (IL-3)-dependent cell line. IL-3-induced tyrosine-phosphorylated STAT5 associated with nuclear PDC-E2 in co-immunoprecipitation analysis. These findings were confirmed by confocal immunofluorescence microscopy showing constant nuclear localization of PDC-E2 and its co-localization with STAT5 after IL-3 stimulation. Similar to mitochondrial PDC-E2, nuclear PDC-E2 was lipoylated and associated with PDC-E1. Overexpression of PDC-E2 in BaF3 cells augmented IL-3-induced STAT5 activity as measured by reporter assay with consensus STAT5-binding sites. Consistent with the reporter data, PDC-E2 overexpression in BaF3 cells led to elevated mRNA levels of endogenous SOCS3 (suppressor of cytokine signaling 3) gene, a known STAT5 target. We further identified two functional STAT5-binding sites in the SOCS3 gene promoter important for its IL-3-inducibility. The observation that both cis-acting elements were essential to detect the stimulatory effect by PDC-E2 strongly supports the role of PDC-E2 in up-regulating the transactivating ability of STAT5. All together, our results reveal a novel function of PDC-E2 in the nucleus. It also raises the possibility of nuclear-mitochondrial crosstalk through the interaction between STAT5 and PDC-E2.