Autophagy-modulating phytochemicals in cancer therapeutics: Current evidences and future perspectives.

Autophagy is an intracellular catabolic self-cannibalism that eliminates dysfunctional cytoplasmic cargos by the fusion of cargo-containing autophagosomes with lysosomes to maintain cyto-homeostasis. Autophagy sustains a dynamic interlink between cytoprotective and cytostatic function during malignant transformation in a context-dependent manner. The antioxidant and immunomodulatory phyto-products govern autophagy and autophagy-associated signaling pathways to combat cellular incompetence during malignant transformation. Moreover, in a close cellular signaling circuit, autophagy regulates aberrant epigenetic modulation and inflammation, which limits tumor metastasis. Thus, manipulating autophagy for induction of cell death and associated regulatory phenomena will embark on a new strategy for tumor suppression with wide therapeutic implications. Despite the prodigious availability of lead pharmacophores in nature, the central autophagy regulating entities, their explicit target, as well as pre-clinical and clinical assessment remains a major question to be answered. In addition to this, the stage-specific regulation of autophagy and mode of action with natural products in regulating the key autophagic molecules, control of tumor-specific pathways in relation to modulation of autophagic network specify therapeutic target in caner. Moreover, the molecular pathway specificity and enhanced efficacy of the pre-existing chemotherapeutic agents in co-treatment with these phytochemicals hold high prevalence for target specific cancer therapeutics. Hence, the multi-specific role of phytochemicals in a cellular and tumor context dependent manner raises immense curiosity for investigating of novel therapeutic avenues. In this perspective, this review discusses about diverse implicit mechanisms deployed by the bioactive compounds in diagnosis and therapeutics approach during cancer progression with special insight into autophagic regulation.

The emerging, multifaceted role of mitophagy in cancer and cancer therapeutics.

Mitophagy is an evolutionarily conserved cellular process which selectively eliminates dysfunctional mitochondria by targeting them to the autophagosome for degradation. Dysregulated mitophagy results in the accumulation of damaged mitochondria, which plays an important role in carcinogenesis and tumor progression. The role of mitophagy receptors and adaptors including PINK1, Parkin, BNIP3, BNIP3L/NIX, and p62/SQSTM1, and the signaling pathways that govern mitophagy are impaired in cancer. Furthermore, the contribution of mitophagy in regulating the metabolic switch may establish a balance between aerobic glycolysis and oxidative phosphorylation for cancer cell survival. Moreover, ROS-driven mitophagy achieves different goals depending on the stage of tumorigenesis. Mitophagy promotes plasticity in the cancer stem cell through the metabolic reconfiguration for better adaption to the tumor microenvironment. In addition, the present review sheds some light on the role of mitophagy in stemness and differentiation during the transition of cell's fate, which could have a crucial role in cancer progression and metastasis. In conclusion, this review deals with the detailed molecular mechanisms underlying mitophagy, along with highlighting the dual role of mitophagy in different aspects of cancer, suggesting it as a possible target in the mitophagy-modulated cancer therapy.

Epigenetic modifications of autophagy in cancer and cancer therapeutics.

Epigenetic alterations, such as DNA methylation, histone modifications and miRNAs, have a significant role play in malignant cellular transformation and metastasis. On the other hand, autophagy has been reported to perform context-dependent roles in cancer; at times, it becomes lethal and abolishes tumorigenesis, whereas, at other instances, it protects cancer cells by providing a rescue mechanism under adverse conditions. Although epigenetics and autophagy are two important and independent cellular processes, various oncogenic and oncosuppressor proteins involve autophagy through epigenetic modifications and different signaling pathways, thereby regulating tumor growth and therapeutic response. Moreover, the importance of epigenetic modification of autophagy in cancer is reflected through its involvement in cancer stem cell maintenance, which in turn, contributes to tumor cell viability during dormancy leading to tumor recurrence. The effects of epigenetic modifications of autophagy in cancer is still ambiguous and less acknowledged; therefore, efforts have been made to understand its detail underlying mechanism to unveil new targets and avenues for better prognosis and diagnosis of cancer.

Molecular interplay of autophagy and endocytosis in human health and diseases.

Autophagy, an evolutionarily conserved process for maintaining the physio-metabolic equilibrium of cells, shares many common effector proteins with endocytosis. For example, tethering proteins involved in fusion like Ras-like GTPases (Rabs), soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs), lysosomal-associated membrane protein (LAMP), and endosomal sorting complex required for transport (ESCRT) have a dual role in endocytosis and autophagy, and the trafficking routes of these processes converge at lysosomes. These common effectors indicate an association between budding and fusion of membrane-bound vesicles that may have a substantial role in autophagic lysosome reformation, by sensing cellular stress levels. Therefore, autophagy-endocytosis crosstalk may be significant and implicates a novel endocytic regulatory pathway of autophagy. Moreover, endocytosis has a pivotal role in the intake of signalling molecules, which in turn activates cascades that can result in pathophysiological conditions. This review discusses the basic mechanisms of this crosstalk and its implications in order to identify potential novel therapeutic targets for various human diseases.

Dysregulation of histone deacetylases in carcinogenesis and tumor progression: a possible link to apoptosis and autophagy.

Dysregulation of the epigenome and constitutional epimutation lead to aberrant expression of the genes, which regulate cancer initiation and progression. Histone deacetylases (HDACs), which are highly conserved in yeast to humans, are known to regulate numerous proteins involved in the transcriptional regulation of chromatin structures, apoptosis, autophagy, and mitophagy. In addition, a non-permissive chromatin conformation is created by HDACs, preventing the transcription of the genes encoding the proteins associated with tumorigenesis. Recently, an expanding perspective has been reported from the clinical trials with HDACis (HDAC inhibitors), which has emerged as a determining target for the study of the detailed mechanisms underlying cancer progression. Therefore, the present review focuses on the comprehensive lucubration of post-translational modifications and the molecular mechanisms through which HDACs alter the ambiguities associated with epigenome, with particular insights into the initiation, progression, and regulation of cancer.

Mitochondrial Heterogeneity in Stem Cells.

Mitochondria are customarily acknowledged as the powerhouse of the cell by virtue of their indispensable role in cellular energy production. In addition, it plays an important role in pluripotency, differentiation, and reprogramming. This review describes variation in the stem cells and their mitochondrial heterogeneity. The mitochondrial variation can be described in terms of structure, function, and subcellular distribution. The mitochondria cristae development status and their localization patterns determine the oxygen consumption rate and ATP production which is a central controller of stem cell maintenance and differentiation. Generally, stem cells show spherical, immature mitochondria with perinuclear distribution. Such mitochondria are metabolically less energetic and low polarized. Moreover, mostly glycolytic energy production is found in pluripotent stem cells with a variation in naïve stem cells which perform oxidative phosphorylation (OXPHOS). This article also describes the structural and functional journey of mitochondria during development. Future insight into underlying mechanisms associated with such alternation in mitochondria of stem cells during embryonic stages could uncover mitochondrial adaptability on cellular demands. Moreover, investigating the importance of mitochondria in pluripotency maintenance might unravel the cause of mitochondrial diseases, aging, and regenerative therapies.

Plant lectins in cancer therapeutics: Targeting apoptosis and autophagy-dependent cell death.

Plant lectins are non-immunoglobin in nature and bind to the carbohydrate moiety of the glycoconjugates without altering any of the recognized glycosyl ligands. Plant lectins have found applications as cancer biomarkers for recognizing the malignant tumor cells for the diagnosis and prognosis of cancer. Interestingly, plant lectins contribute to inducing cell death through autophagy and apoptosis, indicating their potential implication in cancer inhibitory mechanism. In the present review, anticancer activities of major plant lectins have been documented, with a detailed focus on the signaling circuit for the possible molecular targeted cancer therapy. In this context, several lectins have exhibited preclinical and clinical significance, driving toward therapeutic potential in cancer treatment. Moreover, several plant lectins induce immunomodulatory activities, and therefore, novel strategies have been established from preclinical and clinical investigations for the development of combinatorial treatment consisting of immunotherapy along with other anticancer therapies. Although the application of plant lectins in cancer is still in very preliminary stage, advanced high-throughput technology could pave the way for the development of lectin-based complimentary medicine for cancer treatment.

Monitoring and Measuring Mammalian Autophagy.

Macroautophagy (autophagy) is a conserved lysosomal-based intracellular degradation pathway. Here, we present different methods used for monitoring autophagy at cellular level. The methods involve Atg8/LC3 detection and quantification by Western blot, autophagic flux measurement through Western blot, direct fluorescence microscopy or indirect immunofluorescence, and finally traffic light assay using tf-LC3-II. Monitoring autophagic flux is experimentally challenging but obviously a prerequisite for the proper investigation of the process. These methods are suitable for screening purposes and can be used for measurements in cell lysates as well as in living cells. These assays have proven useful for the identification of genes and small molecules that regulate autophagy in mammalian cells.

Identification and Characterization of Stem Cells in Oral Cancer.

Cancer stem cells (CSCs) are a subpopulation of cells within a heterogeneous tumor that have enhanced biologic properties such as increased capacity for self-renewal, increased tumorigenicity, enhanced differentiation capacity, and resistance to chemo- and radiotherapies. This unit describes protocols to isolate and characterize potential cancer stem cells from a solid tumor (oral cancer). This involves creating a single-cell suspension from tumor tissue, tagging the cell subpopulation of interest, and sorting cells into different populations. Finally, the sorted subpopulations can be evaluated for their ability to meet the functional requirements of a CSC, which primarily include increased tumorigenicity in an in vivo xenograft assay. Mastering the protocols in this unit will allow the researcher to study populations of cells that may have properties of CSCs.

Intricate role of mitochondrial lipid in mitophagy and mitochondrial apoptosis: its implication in cancer therapeutics.

The efficacy of chemotherapy is mostly restricted by the drug resistance developed during the course of cancer treatment. Mitophagy, as a pro-survival mechanism, crucially maintains mitochondrial homeostasis and it is one of the mechanisms that cancer cells adopt for their progression. On the other hand, mitochondrial apoptosis, a precisely regulated form of cell death, acts as a tumor-suppressive mechanism by targeting cancer cells. Mitochondrial lipids, such as cardiolipin, ceramide, and sphingosine-1-phosphate, act as a mitophageal signal for the clearance of damaged mitochondria by interacting with mitophagic machinery as well as activate mitochondrial apoptosis via the release of cytochrome c into the cytoplasm. In the recent time, the lipid-mediated lethal mitophagy has also been used as an alternative approach to abolish the survival role of lipid in cancer. Therefore, by targeting mitochondrial lipids in cancer cells, the detailed mechanism linked to drug resistance can be unraveled. In this review, we precisely discuss the current knowledge about the multifaceted role of mitochondrial lipid in regulating mitophagy and mitochondrial apoptosis and its application in effective cancer therapy.