Parthenolide Inhibits the Proliferation of MDA-T32 Papillary Thyroid Carcinoma Cells in Vitro and in Mouse Tumor Xenografts and Activates Autophagy and Apoptosis by Downregulation of the Mammalian Target of Rapamycin (mTOR)/PI3K/AKT Signaling Pathway

Bitter taste signaling in cancer

Pharmacoresistance of cancer cells to many drugs used in chemotherapy remains a major challenge for the treatment of cancer. Multidrug resistance transporters, especially ATP-binding cassette (ABC) transporters, are a major cause of cancer drug resistance since they translocate a broad range of drug compounds across the cell membrane, extruding them out of the cells. The regulation of ABC transporters by bitter taste receptors (TAS2Rs), which might be activated by specific bitter tasting compounds, was described in several types of cells/organs, becoming a potential target for cancer therapy. TAS2Rs expression has been reported in many organs and several types of cancer, like breast, ovarian, prostate, and colorectal cancers, where their activation was shown to be involved in various biological actions (cell survival, apoptosis, molecular transport, among others). Moreover, many TAS2Rs' ligands, such as flavonoids and alkaloids, with well-recognized beneficial properties, including several anticancer effects, have been reported as potential adjuvants in cancer therapies. In this review, we discuss the potential therapeutic role of TAS2Rs and bitter tasting compounds in different types of cancer as a possible way to circumvent chemoresistance.

Targeting mTOR as a Cancer Therapy: Recent Advances in Natural Bioactive Compounds and Immunotherapy

The mammalian target of rapamycin (mTOR) is a highly conserved serine/threonine-protein kinase, which regulates many biological processes related to metabolism, cancer, immune function, and aging. It is an essential protein kinase that belongs to the phosphoinositide-3-kinase (PI3K) family and has two known signaling complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). Even though mTOR signaling plays a critical role in promoting mitochondria-related protein synthesis, suppressing the catabolic process of autophagy, contributing to lipid metabolism, engaging in ribosome formation, and acting as a critical regulator of mRNA translation, it remains one of the significant signaling systems involved in the tumor process, particularly in apoptosis, cell cycle, and cancer cell proliferation. Therefore, the mTOR signaling system could be suggested as a cancer biomarker, and its targeting is important in anti-tumor therapy research. Indeed, its dysregulation is involved in different types of cancers such as colon, neck, cervical, head, lung, breast, reproductive, and bone cancers, as well as nasopharyngeal carcinoma. Moreover, recent investigations showed that targeting mTOR could be considered as cancer therapy. Accordingly, this review presents an overview of recent developments associated with the mTOR signaling pathway and its molecular involvement in various human cancer types. It also summarizes the research progress of different mTOR inhibitors, including natural and synthetised compounds and their main mechanisms, as well as the rational combinations with immunotherapies.

Parthenolide leads to proteomic differences in thyroid cancer cells and promotes apoptosis

Background

Parthenolide has anti-inflammatory, immunomodulatory and anti-cancer activities. But its effect on thyroid cancer cells is still largely unknown.

Methods

Label-free quantitative proteomics and bioinformatics analysis were used to investigate the differentially expressed proteins and their functions in thyroid cancer treated with parthenolide and control pair. Hoechst 33258 fluorescent staining and Annexin V-FITC/PI double staining flow cytometry were used to detected BCPAP cells apoptosis. Parallel reaction monitoring (PRM) and quantitative real-time PCR were used to verify the expression of apoptosis-related differential proteins and their mRNA.

Results

Sixty up-regulated and 96 down-regulated differentially expressed proteins were identified in parthenolide treated thyroid cancer cells BCPAP compared with control thyroid cancer cells. The proteins were mainly relevant to various biological processes that included metabolic processes, response to extracellular stimulus and interaction with host. The molecular functions of most differentially expressed proteins were associated with binding functions and nucleotidyltransferase activity. According to the Kyoto Encyclopedia of Genes and Genomes, the differentially expressed proteins identified are primarily related to various types of metabolic pathways and DNA replication. In cell experiments in vitro, with the increase of the dose of parthenolide, the number of cells gradually decreased, the apoptosis rate gradually increased. PRM verified that the apoptosis-related proteins HMOX1 and GCLM were up-regulated and IL1B was down-regulated in BCPAP cells treated with parthenolide. The mRNA expressions of HMOX1, GCLM, ITGA6 and CASP8 were up-regulated and HSPA1A was down-regulated by PCR.

Conclusions

Parthenolide may influence the biological behavior of human thyroid cancer cells by affecting the expression of proteins related to cell metabolism and DNA replication. Parthenolide induced significant cellular morphological changes and apoptosis in human thyroid cancer cells, leading to an anti-proliferative effect.

Terpenoids' anti-cancer effects: focus on autophagy

Terpenoids are the largest class of natural products, most of which are derived from plants. Amongst their numerous biological properties, their anti-tumor effects are of interest for they are extremely diverse which include anti-proliferative, apoptotic, anti-angiogenic, and anti-metastatic activities. Recently, several in vitro and in vivo studies have been dedicated to understanding the 'terpenoid induced autophagy' phenomenon in cancer cells. Light has already been shed on the intricacy of apoptosis and autophagy relationship. This latter crosstalk is driven by the delicate balance between activating or silencing of certain proteins whereby the outcome is expressed via interrelated signaling pathways. In this review, we focus on nine of the most studied terpenoids and on their cell death and autophagic activity. These terpenoids are grouped in three classes: sesquiterpenoid (artemisinin, parthenolide), diterpenoids (oridonin, triptolide), and triterpenoids (alisol, betulinic acid, oleanolic acid, platycodin D, and ursolic acid). We have selected these nine terpenoids among others as they belong to the different major classes of terpenoids and our extensive search of the literature indicated that they were the most studied in terms of autophagy in cancer. These terpenoids alone demonstrate the complexity by which these secondary metabolites induce autophagy via complex signaling pathways such as MAPK/ERK/JNK, PI3K/AKT/mTOR, AMPK, NF-kB, and reactive oxygen species. Moreover, induction of autophagy can be either destructive or protective in tumor cells. Nevertheless, should this phenomenon be well understood, we ought to be able to exploit it to create novel therapies and design more effective regimens in the management and treatment of cancer.

Phytochemicals in cancer and their effect on the PI3K/AKT-mediated cellular signalling

Protein kinases belong to the largest family of enzymes controlling every aspect of cellular activity including gene expression, cell division, differentiation and metabolism. They are part of major intracellular signalling pathways. Hence, it is not surprising that they are involved in the development of major diseases such as cardiovascular disorders, diabetes, dementia and, most importantly, cancer when they undergo mutations, modifications and unbalanced expression. This review will explore the possibility to draw a connection between the application of natural phytochemicals and the treatment of cancer. We have chosen to focus on the PI3K/AKT cellular signalling pathway which has been shown to be a major target by natural compounds in cell cultures and animal models.

Roles of the SNHG7/microRNA‑9‑5p/DPP4 ceRNA network in the growth and 131I resistance of thyroid carcinoma cells through PI3K/Akt activation

Radioactive iodine (RAI, ¹³¹I) therapy is the main treatment for thyroid carcinoma (TC). Long noncoding RNA (lncRNA)/microRNA (miR) competing endogenous RNA (ceRNA) networks have aroused great interest for their roles in gene expression. The present study aimed to investigate the effect of lncRNA SNHG7 on the growth and ¹³¹I resistance of TC. Differentially expressed lncRNAs in TC and paracancerous tissues were analyzed. The binding of miR-9-5p with small nucleolar RNA host gene 7 (SNHG7) and dipeptidyl-peptidase 4 (DPP4) was identified. Gain- and loss-of-function analyses of SNHG7 and miR-9-5p were performed to determine their effects on the growth and ¹³¹I resistance of TC cells. The activity of the PI3K/Akt pathway was evaluated. Consequently, upregulated SNHG7 was revealed in TC tissues and correlated with ¹³¹I resistance. Silencing of SNHG7 or overexpressing miR-9-5p inhibited the growth and ¹³¹I resistance of TC cells. SNHG7 acted as a ceRNA of miR-9-5p to enhance DPP4 expression. Overexpressed SNHG7 increased DPP4 expression and activated the PI3K/Akt signaling pathway by sponging miR-9-5p. The in vitro results were reproduced in vivo. In summary, the present study provided evidence that the SNHG7/miR-9-5p/DPP4 ceRNA network could promote the growth and ¹³¹I resistance of TC cells via PI3K/Akt activation. The present study may offer novel options for TC treatment.

Natural and Synthetic Lactones Possessing Antitumor Activities

Cancer is one of the leading causes of death globally, accounting for an estimated 8 million deaths each year. As a result, there have been urgent unmet medical needs to discover novel oncology drugs. Natural and synthetic lactones have a broad spectrum of biological uses including anti-tumor, anti-helminthic, anti-microbial, and anti-inflammatory activities. Particularly, several natural and synthetic lactones have emerged as anti-cancer agents over the past decades. In this review, we address natural and synthetic lactones focusing on their anti-tumor activities and synthetic routes. Moreover, we aim to highlight our journey towards chemical modification and biological evaluation of a resorcylic acid lactone, L-783277 (4). We anticipate that utilization of the natural and synthetic lactones as novel scaffolds would benefit the process of oncology drug discovery campaigns based on natural products.

Autophagy-Related Beclin 1 and Head and Neck Cancers

Beclin 1, a positive regulator of autophagy, behaves as a double-edged sword in tumorigenesis. Beclin 1 contributes to tumor suppression by removing defective or damaged organelles and other cellular components; however, its activity can also stimulate cancer initiation and progression. In head and neck cancer, Beclin 1 overexpression promotes autophagy, which limits DNA damage and chromosomal instability and increases necrosis and inflammation by impacting apoptotic and autophagic pathways. This paper reviews the relationship between Beclin 1, carcinogenesis and head and neck cancer prognosis.