The novel IκB kinase β inhibitor IMD-0560 prevents bone invasion by oral squamous cell carcinoma

Plectin promotes tumor formation by B16 mouse melanoma cells via regulation of Rous sarcoma oncogene activity

BACKGROUND

Melanoma is a malignant tumor characterized by high proliferation and aggressive metastasis. To address the molecular mechanisms of the proto-oncogene, Rous sarcoma oncogene (Src), which is highly activated and promotes cell proliferation, migration, adhesion, and metastasis in melanoma. Plectin, a cytoskeletal protein, has recently been identified as a Src-binding protein that regulates Src activity in osteoclasts. Plectin is a candidate biomarker of certain tumors because of its high expression and the target of anti-tumor reagents such as ruthenium pyridinecarbothioamide. The molecular mechanisms by which plectin affects melanoma is still unclear. In this study, we examined the role of plectin in melanoma tumor formation.

METHODS

We used CRISPR/Cas9 gene editing to knock-out plectin in B16 mouse melanoma cells. Protein levels of plectin and Src activity were examined by western blotting analysis. In vivo tumor formation was assessed by subcutaneous injection of B16 cells into nude mice and histological analysis performed after 2 weeks by Hematoxylin-Eosin (H&E) staining. Cell proliferation was evaluated by direct cell count, cell counting kit-8 assays, cyclin D1 mRNA expression and Ki-67 immunostaining. Cell aggregation and adhesion were examined by spheroid formation, dispase-based dissociation assay and cell adhesion assays.

RESULTS

In in vivo tumor formation assays, depletion of plectin resulted in low-density tumors with large intercellular spaces. In vitro experiments revealed that plectin-deficient B16 cells exhibit reduced cell proliferation and reduced cell-to-cell adhesion. Since Src activity is reduced in plectin-deficient melanomas, we examined the relationship between plectin and Src signaling. Src overexpression in plectin knockout B16 cells rescued cell proliferation and improved cell-to-cell adhesion and cell to extracellular matrix adhesion.

CONCLUSION

These results suggest that plectin plays critical roles in tumor formation by promoting cell proliferation and cell-to-cell adhesion through Src signaling activity in melanoma cells.

Bone morphogenetic protein induces bone invasion of melanoma by epithelial-mesenchymal transition via the Smad1/5 signaling pathway

Oral malignant melanoma, which frequently invades the hard palate or maxillary bone, is extremely rare and has a poor prognosis. Bone morphogenetic protein (BMP) is abundantly expressed in bone matrix and is highly expressed in malignant melanoma, inducing an aggressive phenotype. We examined the role of BMP signaling in the acquisition of an aggressive phenotype in melanoma cells in vitro and in vivo. In five cases, immunohistochemistry indicated the phosphorylation of Smad1/5 (p-Smad1/5) in the nuclei of melanoma cells. In the B16 mouse and A2058 human melanoma cell lines, BMP2, BMP4, or BMP7 induces morphological changes accompanied by the downregulation of E-cadherin, and the upregulation of N-cadherin and Snail, markers of epithelial-mesenchymal transition (EMT). BMP2 also stimulates cell invasion by increasing matrix metalloproteinase activity in B16 cells. These effects were canceled by the addition of LDN193189, a specific inhibitor of Smad1/5 signaling. In vivo, the injection of B16 cells expressing constitutively activated ALK3 enhanced zygoma destruction in comparison to empty B16 cells by increasing osteoclast numbers. These results suggest that the activation of BMP signaling induces EMT, thus driving the acquisition of an aggressive phenotype in malignant melanoma.

p130Cas induces bone invasion by oral squamous cell carcinoma by regulating tumor epithelial-mesenchymal transition and cell proliferation

Bone invasion is a critical factor in determining the prognosis of oral squamous cell carcinoma (OSCC) patients. Transforming growth factor β (TGF-β) is abundantly expressed in the bone matrix and is involved in the acquisition of aggressiveness by tumors. TGF-β is also important to cytoskeletal changes during tumor progression. In this study, we examined the relationship between TGF-β signaling and cytoskeletal changes during bone invasion by OSCC. Immunohistochemical staining of OSCC samples from five patients showed the expression of p130Cas (Crk-associated substrate) in the cytoplasm and phosphorylated Smad3 expression in the nucleus in OSCC cells. TGF-β1 induced the phosphorylation of Smad3 and p130Cas, as well as epithelial-mesenchymal transition (EMT) accompanied by the downregulation of the expression of E-cadherin, a marker of epithelial cells, and the upregulation of the expression of N-cadherin, or Snail, a marker of mesenchymal cells, in human HSC-2 cells and mouse squamous cell carcinome VII (SCCVII) cells. SB431542, a specific inhibitor of Smad2/3 signaling, abrogated the TGF-β1-induced phosphorylation of p130Cas and morphological changes. Silencing p130Cas using an short hairpin RNA (shRNA) or small interfering RNA in SCCVII cells suppressed TGF-β1-induced cell migration, invasion, EMT and matrix metalloproteinase-9 (MMP-9) production. Compared with control SCCVII cells, SCCVII cells with silenced p130Cas strongly suppressed zygomatic and mandibular destruction in vivo by reducing the number of osteoclasts, cell proliferation and MMP-9 production. Taken together, these results showed that the expression of TGF-β/p130Cas might be a new target for the treatment of OSCC bone invasion.

[Advances in molecular mechanisms of bone invasion by oral cancer]

Bone invasion by oral cancer is a common clinical problem, which affects the choice of treatment and predicts a poor prognosis. Unfortunately, the molecular mechanism of this phenomenon has not been fully elucidated. Current studies have revealed that oral cancer cells modulate the formation and function of osteoclasts through the expression of a series of signal molecules. Many signal pathways are involved in this process, of which receptor activator of nuclear factor-κB ligand/receptor activator of nuclear factor-κB/osteoprotegerin signaling pathway attracted much attention. In this review, we introduce recent progress in molecular mechanisms of bone invasion by oral cancer.

Salivary Gland Carcinoma: Novel Targets to Overcome Treatment Resistance in Advanced Disease

Salivary gland carcinomas (SGCs) account for <5% of head and neck malignant neoplasms, further subcategorized in over 20 histological subtypes. For the most part, treatment for advanced disease is guided by morphology. SGCs in general respond poorly to a wide array of standard chemotherapy, with short durability, and significant toxicity. More recently, next-generation sequencing provided significant input on the molecular characterization of each SGC subtype, not only improving diagnostic differentiation between morphologically similar tumor types but also identifying novel driver pathways that determine tumor biology and may be amenable to targeted therapy. Among the most common histological subtype is adenoid cystic carcinoma, which often harbors a chromosome translocation resulting in an MYB-NFIB oncogene, with various degrees of Myb surface expression. In a smaller subset, NOTCH1 mutations occur, conferring a more aggressive pattern and potential sensitivity to Notch inhibitors. Salivary duct carcinomas may overexpress Her-2 and androgen receptors, with promising clinical outcomes after exposure to targeted therapies approved for other indications. Secretory carcinoma, previously known as mammary analog secretory carcinoma, is distinguished by an ETV6-NTRK3 fusion that can both help differentiate it from its morphologically similar acinar cell carcinoma and make it susceptible to Trk inhibitors. In the present article, we discuss the molecular abnormalities, their impact on tumor biology, and therapeutic opportunities for the most common SGC subtypes and review published and ongoing clinical trials and future perspectives for this rare disease.

Mutant monocyte chemoattractant protein-1 protein (7ND) inhibits osteoclast differentiation and reduces oral squamous carcinoma cell bone invasion

The seven-amino acid truncated (7ND) protein is an N-terminal deletion mutant of monocyte chemoattractant protein-1 (MCP-1) and it functions as a dominant-negative inhibitor. 7ND and wild-type MCP-1 form a heterodimer, which binds to MCP-1 receptors and inhibits monocyte chemotaxis. In the present study, the 7ND protein was cloned, expressed and purified. An MTT assay revealed that the proliferation of oral squamous cell carcinoma (OSCC) SCC25 cells was not affected following 3 days of treatment with synthetic 7ND protein. Serial dilutions of the 7ND protein were tested for monocyte migration and osteoclast differentiation, and tartrate-resistant acid phosphatase staining demonstrated that significantly fewer osteoclasts were differentiated from cluster of differentiation 14⁺ (CD14⁺) monocytes using magnetic activated cell sorting. Immunofluorescence confirmed these results and significantly less F-actin staining was observed in 7ND-treated osteoclasts. Furthermore, bone invasion was examined by subcutaneously injecting SCC25 cells into the area overlaying the calvariae of nude mice. The results demonstrated that the average tumor volume of SCC25 cells with 7ND protein was similar to the average volume of tumors formed by untreated SCC25 cells. Flow cytometric analysis suggested that the CD14⁺ subpopulation in the bone marrow of 7ND-treated mice was reduced compared with that of untreated mice. Micro-computed tomography imaging revealed significantly less bone resorption in the calvariae injected with SCC25 cells plus the 7ND protein. Taken together, the results of the present study demonstrated the potential therapeutic value of the 7ND protein. The 7ND MCP-1 variant not only functions in vitro to inhibit osteoclast differentiation, but also reduces the progression of bone invasion by OSCC cells in vivo.

Methanol Extract of Holarrhena antidysenterica Inhibits the Growth of Human Oral Squamous Cell Carcinoma Cells and Osteoclastogenesis of Bone Marrow Macrophages

Oral squamous cell carcinoma (OSCC) frequently invades mandibular bone, and outcomes for treatment with surgical resection are typically poor, ultimately resulting in death. Holarrhena antidysenterica L. (Apocynaceae), distributed throughout Sri Lanka and India, has been used as a folk remedy to treat various diseases. Treatment with methanol extract of H. antidysenterica bark (HABE) inhibited cell viability and BrdU incorporation and induced apoptotic cell death in Ca9-22 gingival and HSC-3 tongue SCC cells. Flow cytometric analysis indicated that HABE treatment preferentially induces apoptotic cell death via increasing the sub-G1 peak in Ca9-22 cells and cell cycle arrest at the G1 phase in HSC-3 cells. HABE treatment in the presence of zVAD-fmk, a pan-caspase inhibitor, rescued cell viabilities in both OSCC cell lines. The ratio of Bax to Bcl-2 increased with reductions in the Bcl-2 protein expression, and the activation of caspase 3 and subsequent cleavage of PARP was detected in HABE-treated Ca9-22 and HSC-3 cells. Furthermore, HABE treatment at noncytotoxic concentrations inhibited osteoclast formation in RANKL-stimulated bone marrow macrophages. Taken together, HABE possesses the inhibitory activity on the growth of OSCC cells and antiosteoclastogenic activity. Therefore, HABE may be a promising alternative and complementary agent for preventing and treating OSCC.

The transcriptional co-repressor TLE3 regulates myogenic differentiation by repressing the activity of the MyoD transcription factor

Satellite cells are skeletal muscle stem cells that provide myonuclei for postnatal muscle growth, maintenance, and repair/regeneration in adults. Normally, satellite cells are mitotically quiescent, but they are activated in response to muscle injury, in which case they proliferate extensively and exhibit up-regulated expression of the transcription factor MyoD, a master regulator of myogenesis. MyoD forms a heterodimer with E proteins through their basic helix-loop-helix domain, binds to E boxes in the genome and thereby activates transcription at muscle-specific promoters. The central role of MyoD in muscle differentiation has increased interest in finding potential MyoD regulators. Here we identified transducin-like enhancer of split (TLE3), one of the Groucho/TLE family members, as a regulator of MyoD function during myogenesis. TLE3 was expressed in activated and proliferative satellite cells in which increased TLE3 levels suppressed myogenic differentiation, and, conversely, reduced TLE3 levels promoted myogenesis with a concomitant increase in proliferation. We found that, via its glutamine- and serine/proline-rich domains, TLE3 interferes with MyoD function by disrupting the association between the basic helix-loop-helix domain of MyoD and E proteins. Our findings indicate that TLE3 participates in skeletal muscle homeostasis by dampening satellite cell differentiation via repression of MyoD transcriptional activity.

Platycodin D, a triterpenoid saponin from Platycodon grandiflorum, suppresses the growth and invasion of human oral squamous cell carcinoma cells via the NF-κB pathway

This work was undertaken to explore the effects of platycodin D, a triterpenoid saponin from Platycodon grandiflorum, on the growth and invasiveness of human oral squamous cell carcinoma (OSCC). Platycodin D caused a significant, concentration-dependent inhibition of cell viability and induced significant apoptosis in OSCC cells. Moreover, platycodin D significantly inhibited OSCC cell invasion. At the molecular level, platycodin D increased the amounts of IκBα protein and reduced the expression of phosphorylated NF-κB p65, MMP-2, and MMP-9. Ectopic expression of constitutively active NF-κB p65 prevented platycodin D-mediated induction of apoptosis and suppression of invasion in OSCC cells. In vivo studies confirmed that platycodin D retarded the growth of subcutaneous SCC-4 xenograft tumors and reduced phosphorylation of NF-κB p65. Altogether, platycodin D shows inhibitory activity on OSCC growth and invasion through inactivation of the NF-κB pathway and might provide therapeutic benefits in the treatment of OSCC.

p53 controls colorectal cancer cell invasion by inhibiting the NF-κB-mediated activation of Fascin

p53 mutation is known to contribute to cancer progression. Fascin is an actin-bundling protein and has been recently identified to promote cancer cell migration and invasion through its role in formation of cellular protrusions such as filopodia and invadopodia. However, the relationship between p53 and Fascin is not understood. Here, we have found a new link between them. In colorectal adenocarcinomas, p53 mutation correlated with high NF-κB, Fascin and low E-cadherin expression. Moreover, this expression profile was shown to contribute to poor overall survival in patients with colorectal cancer. Wild-type p53 could inhibit NF-κB activity that repressed the expression of Fascin and cancer cell invasiveness. In contrast, in p53-deficient primary cultured cells, NF-κB activity was enhanced and then activation of NF-κB increased the expression of Fascin. In further analysis, we showed that NF-κB was a key determinant for p53 deletion-stimulated Fascin expression. Inhibition of NF-κB /p65 expression by pharmacological compound or p65 siRNA suppressed Fascin activity in p53-deficient cells. Moreover, restoration of p53 expression decreased the activation of Fascin through suppression of the NF-κB pathway. Taken together, these data suggest that a negative-feedback loop exists, whereby p53 can suppress colorectal cancer cell invasion by inhibiting the NF-κB-mediated activation of Fascin.

IKK inhibitor suppresses epithelial-mesenchymal transition and induces cell death in prostate cancer

IκB kinase (IKK)/nuclear factor κB (NF-κB) pathway activation is a key event in the acquisition of invasive and metastatic capacities in prostate cancer. A potent small-molecule compound, BMS-345541, was identified as a highly selective IKKα and IKKβ inhibitor to inhibit kinase activity. This study explored the effect of IKK inhibitor on epithelial-mesenchymal transition (EMT), apoptosis and metastasis in prostate cancer. Here, we demonstrate the role of IKK inhibitor reducing proliferation and inducing apoptosis in PC-3 cells. Furthermore, BMS345541 inhibited IκBα phosphorylation and nuclear level of NF-κB/p65 in PC-3 cells. We also observed downregulation of the N-cadherin, Snail, Slug and Twist protein in a dose-dependent manner. BMS‑345541 induced upregulation of the epithelial marker E-cadherin and phosphorylated NDRG1 at protein level. Moreover, BMS‑345541 reduced invasion and metastasis of PC-3 cells in vitro. In conclusion, IKK has a key role in both EMT and apoptosis of prostate cancer. IKK inhibitor can reverse EMT and induce cell death in PCa cells. IKK was identified as a potential target structure for future therapeutic intervention in PCa.

Establishment of a xenograft model to explore the mechanism of bone destruction by human oral cancers and its application to analysis of role of RANKL

BACKGROUND

The molecular mechanism underlying bone invasion caused by oral squamous cell carcinoma (OSCC) is not well understood. To elucidate the molecular mechanism, the development of more suitable xenograft models mimicking human mandibular bone destruction by OSCC has been required.

MATERIALS AND METHODS

Human OSCC cell lines, HSC3, HSC3-C1, and HSC3-R2, were injected in the periosteal region of the mandible in athymic mice, and the bone destruction was analyzed. Receptor activators of nuclear factor κ-B ligand (RANKL) mRNA and protein expression levels were measured in the OSCC cell lines. Antibody that specifically neutralizes mouse RANKL and human RANKL, respectively, was injected into HSC3-cell-transplanted mice.

RESULTS

Transplantation of HSC3 cells induced mandibular bone destruction. Histological examination revealed numerous osteoclasts on the bone destruction surface. Fibroblastic cell intervention between the cancer nests and resorbing bone surface was observed in a similar fashion to those observed in human OSCC cases. The number of osteoclasts and fibroblasts was significantly correlated. Bone destruction induced by the transplantation of HSC3 cells was reduced by injection of an antibody that specifically neutralizes mouse RANKL. Transplantation of HSC3-R2 cells, which overexpresses RANKL, induced advanced bone destruction compared to that of HSC3-C1 cells, which only overexpress the empty vector.

CONCLUSIONS

We established a useful xenograft model for investigating the molecular mechanism underlying the bone destruction induced by OSCC in the jaw. This model will be used to investigate the precise roles of several cytokines synthesized by both cancer cells and fibroblastic cells in OSCC-associated bone destruction in the jaw.