Enhanced anti-melanoma efficacy of interferon alfa-2b via inhibition of Shp2

Double-edged roles of protein tyrosine phosphatase SHP2 in cancer and its inhibitors in clinical trials

Phosphorylation is a reversible post-translational modification regulated by phosphorylase and dephosphorylase to mediate important cellular events. Src homology-2-containing protein tyrosine phosphatase 2 (SHP2) encoded by PTPN11 is the first identified oncogenic protein in protein tyrosine phosphatases family. Serving as a convergent node, SHP2 is involved in multiple cascade signaling pathways including Ras-Raf-MEK-ERK, PI3K-AKT, JAK-STAT and PD-1/PD-L1 pathways. Especially, the double-edged roles of SHP2 based on the substrate specificity in various biological contexts dramatically increase the effect complexity in different SHP2-associated diseases. Evidences suggest that by collaborating with other mutations in associated pathways, dysregulation of SHP2 contributes to the pathogenesis of different cancers, making SHP2 a promising therapeutic target for cancer treatment. SHP2 can either act as oncogenic factor or tumor suppressor in different diseases, and both the conserved catalytic dephosphorylation mechanism and the unique allosteric regulation mechanism of SHP2 provide opportunities for the development of SHP2 inhibitors and activators. To date, several small-molecule SHP2 inhibitors have advanced into clinical trials for mono- or combined therapy of cancers. Moreover, SHP2 activators and proteolysis-targeting chimera (PROTAC)-based degraders also display therapeutic promise. In this review, we comprehensively summarize the overall structures, regulation mechanisms, double-edged roles of SHP2 in both physiological and carcinogenic pathways, and SHP2 inhibitors in clinical trials. SHP2 activators and degraders are also briefly discussed. This review aims to provide in-depth understanding of the biological roles of SHP2 and highlight therapeutic potential of targeting SHP2.

Paclitaxel-Loaded Biotinylated Fe2+-Doped Carbon Dot: Combination Therapy in Cancer Treatment

The present research work delineates the design and preparation of covalently tailored biotinylated Fe²⁺-doped carbon dots (FCD_b). The FCD_b was successfully used as a pro-drug activator, diagnostic probe, and target-specific delivery vehicle for anticancer drug paclitaxel in pro-drug-free drug combination therapy of cancer treatment. Fe²⁺-doped carbon dot was synthesized via the hydrothermal method (FCD). The surface of FCD was covalently modified with cancer cell targeting ligand biotin (FCD_b). Microscopic and spectroscopic methods were used to characterize aqueous soluble FCD and FCD_b. Both FCD and FCD_b emit blue fluorescence under UV light irradiation. FCD and FCD_b can effectively sense H₂O₂ by fluorescence quenching as well as activate H₂O₂ (pro-drug), which oxidatively damage the DNA through the generation of reactive oxygen species (ROS: superoxide (O₂^•-), hydroxyl radical (^•OH), etc). Both FCD and FCD_b were utilized as selective cellular markers for cancer cell B16F10 owing to their high H₂O₂ content, which was more distinct in the case of FCD_b due to the overexpression of biotin receptor in cancer cell. Anticancer drug paclitaxel (PTX)-loaded FCD_b (FCD_b-PTX) was employed for the selective killing of B16F10 cancer cells. This pro-drug-free drug formulation (FCD_b-PTX) exhibited ∼2.7- to 3.5-fold higher killing of B16F10 cells mostly via early as well as late apoptotic path in comparison to noncancer NIH3T3 cells through the synergistic action of ROS (generated from H₂O₂ in the presence of FCD_b) and anticancer effect of PTX. Hence, this newly developed FCD_b-PTX can act as a potential theranostic agent in the domain of combination therapy of cancer treatment.

Oncogenic Tyrosine Phosphatases: Novel Therapeutic Targets for Melanoma Treatment

Despite a large number of therapeutic options available, malignant melanoma remains a highly fatal disease, especially in its metastatic forms. The oncogenic role of protein tyrosine phosphatases (PTPs) is becoming increasingly clear, paving the way for novel antitumor treatments based on their inhibition. In this review, we present the oncogenic PTPs contributing to melanoma progression and we provide, where available, a description of new inhibitory strategies designed against these enzymes and possibly useful in melanoma treatment. Considering the relevance of the immune infiltrate in supporting melanoma progression, we also focus on the role of PTPs in modulating immune cell activity, identifying interesting therapeutic options that may support the currently applied immunomodulating approaches. Collectively, this information highlights the value of going further in the development of new strategies targeting oncogenic PTPs to improve the efficacy of melanoma treatment.

Photosensitizer Tailored Surface Functionalized Carbon Dots for Visible Light Induced Targeted Cancer Therapy

Herein, a photosensitizer (riboflavin) tailored surface functionalized carbon dot (RCD1s) was designed to utilize it in visible light induced targeted cancer therapy. At first, phenylboronic acid appended biotinylated blue emitting carbon dot (CD1s) was synthesized. Riboflavin having "diol" moiety was covalently linked with this CD1s to prepare RCD1s by using complementary boronate-diol linkage. Lewis acid-base interaction facilitated the covalent linkage formation between the surface functionalizing agent of CD1s and riboflavin to develop water-soluble, green emitting RCD1s. Interestingly, this newly synthesized RCD1s has the ability to produce reactive oxygen species (ROS) such as hydroxyl and superoxide radicals under exposure of visible light (wavelength: 460-490 nm). These ROS also can destroy the structure of DNA by oxidative pathway. Thus, under irradiation of visible light (wavelength: 460-490 nm), RCD1s was found to kill HeLa and B16F10 melanoma cells over noncancer cell NIH3T3 by ∼5-fold higher efficacy through ROS induced oxidative DNA damage. The presence of biotin on the surface of the riboflavin tethered carbon dot is essential for the selective killing of cancer cells over normal cells. In the presence of UV light (340-420 nm), RCD1s showed no notable killing of cancer cells as well as normal cells. Besides, RCD1s in the presence of visible light selectively stained HeLa and B16F10 cells over noncancerous cell NIH3T3 by exploiting its fluorescence and cancer cell targeting moiety, biotin. Hence, the newly developed RCD1s can be utilized in theranostic applications including bioimaging and selective killing of cancer cells in the presence of visible light (460-490 nm).

The Oncolytic Virus VSV-GP Is Effective against Malignant Melanoma

Previously, we described VSV-GP, a modified version of the vesicular stomatitis virus, as a non-neurotoxic oncolytic virus that is effective for the treatment of malignant glioblastoma and ovarian cancer. Here, we evaluate the therapeutic efficacy of VSV-GP for malignant melanoma. All of the human, mouse, and canine melanoma cell lines that were tested, alongside most primary human melanoma cultures, were infected by VSV-GP and efficiently killed. Additionally, we found that VSV-GP prolonged the survival of mice in both a xenograft and a syngeneic mouse model. However, only a few mice survived with long-term tumor remission. When we analyzed the factors that might limit VSV-GP's efficacy, we found that vector-neutralizing antibodies did not play a role in this context, as even after eight subsequent immunizations and an observation time of 42 weeks, no vector-neutralizing antibodies were induced in VSV-GP immunized mice. In contrast, the type I IFN response might have contributed to the reduced efficacy of the therapy, as both of the cell lines that were used for the mouse models were able to mount a protective IFN response. Nevertheless, early treatment with VSV-GP also reduced the number and size of lung metastases in a syngeneic B16 mouse model. In summary, VSV-GP is a potent candidate for the treatment of malignant melanoma; however, factors limiting the efficacy of the virus need to be further explored.

Glucose oxidase mediated targeted cancer-starving therapy by biotinylated self-assembled vesicles

Glucose oxidase (GOx) mediated targeted cancer-starving therapy, by blocking the energy supply to cancer cells, has been demonstrated using GOx encapsulating monolayer vesicles of a trimesic acid based biotinylated amphiphile (TMB). GOx, loaded within the TMB vesicles, was selectively delivered inside the cancer cells, resulting in ∼6-fold higher killing of cancer cells compared to normal cells.

Interferons and their stimulated genes in the tumor microenvironment

Constitutive expression of interferons (IFNs) and activation of their signaling pathways have pivotal roles in host responses to malignant cells in the tumor microenvironment. IFNs are induced by the innate immune system and in tumors through stimulation of Toll-like receptors (TLRs) and through other signaling pathways in response to specific cytokines. Although in the oncologic context IFNs have been thought of more as exogenous pharmaceuticals, the autocrine and paracrine actions of endogenous IFNs probably have even more critical effects on neoplastic disease outcomes. Through high-affinity cell surface receptors, IFNs modulate transcriptional signaling, leading to regulation of more than 2,000 genes with varying patterns of temporal expression. Induction of the gene products by both unphosphorylated and phosphorylated STAT1 after ligand binding results in alterations in tumor cell survival, inhibition of angiogenesis, and augmentation of actions of T, natural killer (NK), and dendritic cells. The interferon-stimulated gene (ISG) signature can be a favorable biomarker of immune response but, in a seemingly paradoxical finding, a specific subset of the full ISG signature indicates an unfavorable response to DNA-damaging interventions such as radiation. IFNs in the tumor microenvironment thus can alter the emergence, progression, and regression of malignancies.

Upregulation of Src homology phosphotyrosyl phosphatase 2 (Shp2) expression in oral cancer and knockdown of Shp2 expression inhibit tumor cell viability and invasion in vitro

OBJECTIVE

This study investigated the clinical significance of Shp2 protein expression in oral squamous cell carcinoma (OSCC) and elucidated its biologic significance in OSCC cells.

STUDY DESIGN

A total of 88 OSCC cases were used to assess Shp2 expression, out of which 70 were for immunohistochemistry and 18 paired tumors vs normal tissues were for Western blot of Shp2 expression. OSCC cells were used to assess the effects of Shp2 knockdown for cell viability, apoptosis, invasion, and protein expressions.

RESULTS

Expression of Shp2 protein was significantly upregulated in OSCC tissues compared with the normal tissues, and Shp2 overexpression was associated with advanced tumor clinical stages and lymph node metastasis ex vivo. Knockdown of Shp2 expression in vitro inhibited OSCC cell viability and invasion but induced apoptosis by regulating expression of the apoptosis-related proteins.

CONCLUSIONS

The data indicated that Shp2 may play an important role in OSCC progression. Further studies will investigate whether a target of Shp2 expression could be a novel therapeutic strategy for clinical control of OSCC.

Loss of SHP-2 activity in CD4+ T cells promotes melanoma progression and metastasis

The Src homology 2 domain-containing tyrosine phosphatase 2 (SHP-2) has been reported to have both tumor-promoting and tumor-suppressing roles in tumorigenesis. However, the role of SHP-2 in tumor immunity remains unclear. Here we observed progressively lower levels of phosphorylated SHP-2 in tumor-associated CD4⁺ T cells during melanoma development in a murine model. Similarly, the levels of phosphorylated SHP-2 in the CD4⁺ T cells of human melanoma specimens revealed a decrease paralleling cancer development. The CD4⁺ T cell-specific deletion of SHP-2 promoted melanoma metastasis in mice. Furthermore, SHP-2 deficiency in CD4⁺ T cells resulted in the increased release of inflammatory cytokines, especially IL-6, and the enhanced accumulation of tumor-promoting myeloid-derived suppressor cells (MDSCs) in tumor-bearing mice. An IL-6-neutralizing antibody reduced MDSC accumulation and inhibited tumor growth in CD4⁺ T-cell-specific SHP-2-knockout mice. Our results suggest that SHP-2 in CD4⁺ T cells plays an important role in preventing melanoma progression and metastasis.