Signal transducer and activators of transcription 3 regulates cryptotanshinone-induced apoptosis in human mucoepidermoid carcinoma cells

The multifaceted role of STAT3 pathway and its implication as a potential therapeutic target in oral cancer

Oral cancer is one of the leading causes of cancer-related deaths, and it has become a matter of serious concern due to the alarming rise in its incidence rate worldwide. Despite recent advancements in oral cancer treatment strategies, there are no significant improvements in patient's survival rate. Among the numerous cell signaling pathways involved in oral cancer development and progression, STAT3 is known to play a multifaceted oncogenic role in shaping the tumor pathophysiology. STAT3 hyperactivation in oral cancer contributes to survival, proliferation, invasion, epithelial to mesenchymal transition, metastasis, immunosuppression, chemoresistance, and poor prognosis. A plethora of pre-clinical and clinical studies have documented the role of STAT3 in the initiation and development of oral cancer and showed that STAT3 inhibition holds significant potential in the prevention and treatment of this cancer. However, to date, targeting STAT3 activation mainly involves inhibiting the upstream signaling molecules such as JAK and IL-6 receptors. The major challenge in targeting STAT3 lies in the complexity of its phosphorylation- and dimerization-independent functions, which are not affected by disrupting the upstream regulators. The present review delineates the significance of the STAT3 pathway in regulating various hallmarks of oral cancer. In addition, it highlights the STAT3 inhibitors identified to date through various preclinical and clinical studies that can be employed for the therapeutic intervention in oral cancer treatment.

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.

Cryptotanshinone Induces Cell Cycle Arrest and Apoptosis of NSCLC Cells through the PI3K/Akt/GSK-3β Pathway

Cryptotanshinone (CTT) is a natural product and a quinoid diterpene isolated from the root of the Asian medicinal plant, Salvia miltiorrhizabunge. Notably, CTT has a variety of anti-cancer actions, including the activation of apoptosis, anti-proliferation, and reduction in angiogenesis. We further investigated the anti-cancer effects of CTT using MTS, LDH, and Annexin V assay, DAPI staining, cell cycle arrest, and Western blot analysis in NSCLC cell lines. NSCLC cells treated with CTT reduced cell growth through PI3K/Akt/GSK3β pathway inhibition, G0/G1 cell cycle arrest, and the activation of apoptosis. CTT induced an increase of caspase-3, caspase-9, poly-ADP-ribose polymerase (PARP), and Bax, as well as inhibition of Bcl-2, survivin, and cellular-inhibitor of apoptosis protein 1 and 2 (cIAP-1 and -2). It also induced G0/G1 phase cell cycle arrest by decreasing the expression of the cyclin A, cyclin D, cyclin E, Cdk 2, and Cdk 4. These results highlight anti-proliferation the latent of CTT as natural therapeutic agent for NSCLC. Therefore, we investigated the possibility of CTT as an anti-cancer agent by comparing with GF, which is a representative anti-cancer drug.

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.

Niclosamide inhibition of STAT3 synergizes with erlotinib in human colon cancer

Niclosamide, an anthelmintic drug approved by the US Food and Drug Administration against cestodes, is used to treat tapeworm infection. In this study, we show that niclosamide can potentially inhibit signal transducer and activator of transcription 3 (STAT3) in colon cancer cell lines. Combined inhibition of epidermal growth factor receptor and STAT3 by erlotinib and niclosamide synergistically induces apoptosis and antiproliferation in colon cancer cell lines. Our findings suggest that erlotinib and niclosamide combination provides an effective therapeutic approach to improving the prognosis of colon cancer.

Cryptotanshinone potentiates the antitumor effects of doxorubicin on gastric cancer cells via inhibition of STAT3 activity

Objective To investigate the synergistic effects of cryptotanshinone (CPT) and doxorubicin (DOXO) on induction of apoptosis in human gastric cancer cells and the mechanisms. Methods Cell proliferation and apoptosis were detected using the CCK8 assay and AnnexinV/PI staining, respectively. Western blotting was used to determine the levels and phosphorylation of proteins encoded by STAT3-regulated genes and the cleaved forms of caspases and PARP. Results CPT significantly potentiated the antiproliferative effect of DOXO in gastric cancer cell lines. CPT combined with DOXO induced apoptosis and cleavage of caspases-3,-7,-9 as well as PARP. CPT or a STAT3 siRNA significantly suppressed constitutive and IL-6-induced phosphorylation of STAT3 Tyr705, decreasing the levels of proteins encoded by STAT3-target genes (Bcl-xL, Mcl-1, survivin, and XIAP). Conclusions CPT enhanced the anticancer activity of DOXO in gastric cancer cells via STAT3 inactivation and suppression STAT3-regulated antiapoptotic gene expression, indicating that DOXO combined with CPT may serve as effective therapy for gastric cancer.

Cryptotanshinone inhibits lung tumor growth by increasing CD4+ T cell cytotoxicity through activation of the JAK2/STAT4 pathway

Cryptotanshinone is one of the fat-soluble phenanthrene quinone components. In vitro studies have shown that tanshinone compounds can inhibit the proliferation of various tumor cells and affect cell cycle distribution. The aim of the present study was to better understand the effect of cryptotanshinone on the inhibition of small cell lung cancer by cytotoxic cluster of differentiation (CD)4⁺ T cells through activation of the Janus kinase 2/signal transducer and activator of transcription 4 (JAK2/STAT4) pathway. The Cell Counting kit-8 assay and the lactate dehydrogenase assay were used to analyze the cell proliferation of H446 and CD4⁺ T cells, and the cell cytotoxicity of CD4⁺ and CD8⁺ T cells, respectively. JAK2 and STAT4 protein expression was measured by western blot analysis. Cryptotanshinone effectively inhibited the tumor growth of the H446 cells and the cell proliferation of the CD4⁺ T cells. Treatment with cryptotanshinone increased the cytotoxicity of the CD4⁺ T cells, but could not affect the cytotoxicity of the CD8⁺ T cells. Meanwhile, cryptotanshinone induced phosphorylated (p)-JAK2 and p-STAT4 protein expression in the CD4⁺ T cells. These results suggest that cryptotanshinone inhibits the cell growth of lung tumors by increasing CD4⁺ T cell toxicity through activation of the JAK2/STAT4 pathway.