Inhibition of myeloid cell leukemia-1: Association with sorafenib-induced apoptosis in human mucoepidermoid carcinoma cells and tumor xenograft

Exploiting BRAF mutations in the therapeutic approach towards oral and maxillofacial tumors

Oral and maxillofacial tumors pose a significant clinical challenge due to their tendency to recur, despite advancements in surgical removal techniques. The jaw's intricate structure further complicates treatments and affects patient quality of life. Consequently, emphasis has shifted towards pharmacological interventions, to potentially reduce invasive surgical procedures. One promising approach targets BRAF mutations, specifically the common V600E mutation. BRAF, a critical protein kinase, regulates cell growth and differentiation via the RAS-RAF-MEK-ERK-MAP kinase pathway. A specific nucleotide change at position 1799, swapping Thymine (T) for Adenine (A), results in the V600E mutation, causing unchecked cell growth. This mutation is common in certain oral and maxillofacial tumors like ameloblastoma. A recent neoadjuvant therapy targeting BRAF, involving the use of dabrafenib and trametinib, has showcased a promising, safe, and effective strategy for organ preservation in the treatment of mandibular ameloblastoma. This convergence of molecular insights and targeted therapies holds the key to managing BRAF-mutated oral and maxillofacial tumors effectively, promising improved patient outcomes.

Myeloid cell leukemia-1 expression in cancers of the oral cavity: a scoping review

Background

B cell lymphoma-2 (Bcl-2) family members play important roles in cell survival as well as cell death. The role of myeloid cell leukemia-1 (Mcl-1), an important member of the Bcl-2 family, is well established in hematopoietic malignancies. However, the association between Mcl-1 and oral cavity, cancers is not clearly defined.

Methods

A scoping review was conducted until June 30, 2021, using four major databases, PubMed, Scopus, Web of Science, and Embase. Medical subject headings keywords for Mcl-1, along with its other identifiers, and head and neck cancers (only oral cavity tumors) were used to evaluate the expression, function, molecular association, and therapeutic approach of Mcl-1 in oral cavity cancers and precancers.

Findings

Mcl-1 expression was associated with the progression of oral cavity cancers. The molecular mechanism and pathways of Mcl-1 in oral cavity cancers established via experimental results have been highlighted in this review. Moreover, the various synthetic and naturally derived therapeutic agents targeting Mcl-1 have been documented.

Novelty/Improvement

Based on our present review, Mcl-1 appears to be an effective anticancer target that can be used in the therapeutic management of oral cancers.

Cell culture models of oral mucosal barriers: A review with a focus on applications, culture conditions and barrier properties

Understanding the function of oral mucosal epithelial barriers is essential for a plethora of research fields such as tumor biology, inflammation and infection diseases, microbiomics, pharmacology, drug delivery, dental and biomarker research. The barrier properties are comprised by a physical, a transport and a metabolic barrier, and all these barrier components play pivotal roles in the communication between saliva and blood. The sum of all epithelia of the oral cavity and salivary glands is defined as the blood-saliva barrier. The functionality of the barrier is regulated by its microenvironment and often altered during diseases. A huge array of cell culture models have been developed to mimic specific parts of the blood-saliva barrier, but no ultimate standard in vitro models have been established. This review provides a comprehensive overview about developed in vitro models of oral mucosal barriers, their applications, various cultivation protocols and corresponding barrier properties.

Nitidine chloride represses Mcl-1 protein via lysosomal degradation in oral squamous cell carcinoma

BACKGROUND

We have shown previously that nitidine chloride (NC) induces apoptosis via inhibition of signal transducer and activator of transcription 3 (STAT3). However, its downstream molecules are not fully understood yet. Here, we report that NC as STAT3 inhibitor downregulates myeloid cell leukemia-1 (Mcl-1) protein in HSC-3 and HSC-4 human oral squamous cell carcinoma (OSCC) cells and a nude mouse tumor xenograft model.

METHODS

This study investigated the effects of NC on Mcl-1 expression in HSC-3 and HSC-4 cells using Western blotting, RT-PCR, and dual-luciferase assay. Immunohistochemistry was employed to evaluate Mcl-1 expression levels in mouse tumor tissues. Construction of Mcl-1 overexpression vector and transient transfection was done to test the apoptosis of HSC-3 cells.

RESULTS

Nitidine chloride did not affect either mRNA level or promoter activity of Mcl-1, and the decrease in Mcl-1 protein by NC was caused by lysosome-dependent degradation, but not proteasome-dependent degradation. The overexpression of Mcl-1 protein in OSCC cell lines was sufficient to block the induction of apoptosis. In addition, NC strongly reduced the expression level of Mcl-1 protein compared with other STAT3 inhibitors such as cryptotanshione and S3I-201 in OSCCs.

CONCLUSIONS

Our findings suggest that NC triggers apoptosis via lysosome-dependent Mcl-1 protein degradation and could be chosen as a promising chemotherapeutic candidate against human OSCCs.

Apoptosis induced by methanol extract of Potentilla discolor in human mucoepidermoid carcinoma cells through STAT3/PUMA signaling axis

Potentilla discolor has been used in traditional Chinese medicine for the treatment of hyperglycemia. However, the potential role of Potentilla discolor against cancer and its mode of action remain to be fully elucidated. The present study explored the apoptotic effect of methanol extract of Potentilla discolor (MEPD) in human mucoepidermoid carcinoma (MEC) cell lines of salivary glands. MEPD markedly suppressed the growth and induced apoptotic cell death in MC3 and YD15 cells. MEPD treatment significantly upregulated the expression of PUMA and reduced STAT3 phosphorylation. Overexpression of STAT3 partially recovered the growth of MEC cells inhibited by MEPD. In addition, dephosphorylation of STAT3 by cryptotanshinone (a potent STAT3 inhibitor) was sufficient to inhibit the growth of MEC cells and induce apoptosis via affecting PUMA protein. These results suggest that MEPD has a potential anticancer property via the STAT3/PUMA signaling axis in human MEC cells of salivary gland.

Nitidine chloride acts as an apoptosis inducer in human oral cancer cells and a nude mouse xenograft model via inhibition of STAT3

Nitidine chloride (NC) is a natural alkaloid compound derived from the plant Zanthoxylum nitidum and is known for its therapeutic anticancer potential. In this study, we investigated the effects of NC on growth and signaling pathways in human oral cancer cell lines and a tumor xenograft model. The apoptotic effects and related molecular targets of NC on human oral cancer were investigated using trypan blue exclusion assay, DAPI staining, Live/Dead assay, Western blotting, Immunohistochemistry/Immunofluorescence and a nude mouse tumor xenograft. NC decreased cell viability in both HSC3 and HSC4 cell lines; further analysis demonstrated that cell viability was reduced via apoptosis. STAT3 was hyper-phosphorylated in human oral squamous cell carcinoma (OSCC) compared with normal oral mucosa (NOM) and dephosphorylation of STAT3 by the potent STAT3 inhibitor, cryptotanshinone or NC decreased cell viability and induced apoptosis. NC also suppressed cell viability and induced apoptosis accompanied by dephosphorylating STAT3 in four other oral cancer cell lines. In a tumor xenograft model bearing HSC3 cell tumors, NC suppressed tumor growth and induced apoptosis by regulating STAT3 signaling without liver or kidney toxicity. Our findings suggest that NC is a promising chemotherapeutic candidate against human oral cancer.

Sorafenib potentiates ABT-737-induced apoptosis in human oral cancer cells

OBJECTIVE

The mimetic BH3 ABT-737, a potent inhibitor of anti-apoptotic Bcl-2 family proteins, has potential as anti-cancer drug in many cancers. Recently, patients treated with ABT-737 have developed drug tolerance during cancer therapy. Therefore, we examined whether ABT-737 is effective in killing MC-3 and HSC-3 human oral cancer cells either alone or in combination with the oncogenic kinase inhibitor, sorafenib.

DESIGN

The potentiating activities of sorafenib in ABT-737-induced apoptosis were determined using trypan blue exclusion assay, DAPI staining, cell viability assay and Western blot analysis.

RESULTS

Combined use of ABT-737 and sorafenib synergistically suppressed cell viability and induced apoptosis compared with either compound individually. The combination of ABT-737 and sorafenib altered only Bax and Bak proteins and their activations, resulting in mitochondrial translocation of Bax from the cytosol. Additionally, combination treatment-mediated apoptosis may be correlated with ERK and STAT3 pathways.

CONCLUSIONS

These results suggest that sorafenib may effectively overcome ABT-737 resistance to apoptotic cell death, which can be a new potential chemotherapeutic strategy against human oral cancer.

Myeloid cell leukemia-1 is a molecular indicator for malignant transformation of oral lichen planus

Oral lichen planus (OLP), characterized by a chronic mucocutaneous inflammatory condition, is a common disease of the oral cavity. Retrospective and prospective epidemiological data suggest that OLP is considered to have malignant potential. However, it is unclear as to which types of molecules may cause malignant transformation of OLP. In the present study, the presence of myeloid cell leukemia-1 (Mcl-1) and B-cell lymphoma-2 (Bcl-2) was studied by western blot analysis in 11 OLP and three normal oral mucosa (NOM) samples and in two human oral cancer cell lines. The functional role of Mcl-1 in oral cancer cells was analyzed using a trypan blue exclusion assay and soft agar assay. Mcl-1 was strongly expressed in the OLP and the two oral cancer cell lines compared with NOM, whereas Bcl-2 was not. Sorafenib and mithramycin A decreased cell viability in MC-3 and HSC-3 oral cancer cells and at same concentration they reduced the expression level of Mcl-1 in the two cell lines. The two chemicals affected Mcl-1 protein and significantly inhibited neoplastic cell transformation in the two cell lines. We suggest that the malignant potential of OLP may be associated with the expression of Mcl-1, and that downregulation of Mcl-1 may prevent malignant transformation of OLP to oral cancer.