The Autophagic Process Occurs in Human Bone Metastasis and Implicates Molecular Mechanisms Differently Affected by Rab5a in the Early and Late Stages

PDZK1-Interacting Protein 1(PDZKIP1) Inhibits Goat Subcutaneous Preadipocyte Differentiation through Promoting Autophagy

PDZK1IP1 is highly expressed in tumor tissue and has been identified as a tumor biomarker. However, the role of PDZK1IP1 in goat subcutaneous preadipocyte differentiation remains largely unknown. The molecular mechanism of autophagy in regulating the differentiation of goat subcutaneous preadipocytes has not been clarified yet. In our study, PDZK1IP1 gain of function and loss of function were performed to reveal its functions in preadipocyte differentiation and autophagy. Our results showed that the overexpression of PDZK1IP1 inhibited the differentiation of goat subcutaneous preadipocytes, whereas it promoted autophagy. Consistently, the knockdown of PDZK1IP1 demonstrated the opposite tendency. Next, we investigated whether PDZK1IP1 inhibited the differentiation of goat preadipocytes by regulating autophagy. We found that inhibiting autophagy can rescue the PDZK1IP1-induced differentiation restraint in goat subcutaneous preadipocytes. In conclusion, PDZK1IP1 acts as a regulator of adipogenesis, and inhibits goat subcutaneous preadipocyte differentiation through promoting autophagy. Our results will contribute to further understanding the role and mechanism of PDZK1IP1 in controlling adipogenesis.

The Role of Autophagy in Breast Cancer Metastasis

Patient morbidity and mortality is significantly increased in metastatic breast cancer. The metastasis process of breast cancer is very complicated and is delicately controlled by various factors. Autophagy is one of the important regulatory factors affecting metastasis in breast cancer by engaging in cell mobility, metabolic adaptation, tumor dormancy, and cancer stem cells. Here, we discuss the effects of autophagy on metastasis in breast cancer and assess the potential use of autophagy modulators for metastasis treatment.

Ursolic Acid Derivative UA232 Promotes Tumor Cell Apoptosis by Inducing Endoplasmic Reticulum Stress and Lysosomal Dysfunction

Due to increased drug and radiation tolerance, there is an urgent need to develop novel anticancer agents. In our previous study, we performed a series of structural modifications of ursolic acid (UA), a natural product of pentacyclic triterpenes, and found UA232, a derivative with stronger anti-tumor activity. In vitro experiments showed that UA232 inhibited proliferation, induced G0/G1 arrest, and promoted apoptosis in human breast cancer and cervical cancer cells. Mechanistic studies revealed that UA232 promoted apoptosis and induced protective autophagy via the protein kinase R-like endoplasmic reticulum kinase/activating transcription factor 4/C/EBP homologous protein-mediated endoplasmic reticulum stress. In addition, we also found that UA232 induced lysosomal biogenesis, increased lysosomal membrane permeability, promoted lysosomal protease release, and led to lysosome-dependent cell death. Furthermore, UA232 suppressed tumor growth in a mouse xenograft model. In conclusion, our study revealed that UA232 exerts multiple pharmacological effects against breast and cervical cancers by simultaneously triggering endoplasmic reticulum stress and lysosomal dysfunction. Thus, UA232 may be a promising drug candidate for cancer treatment.

Bone Metastatic Breast Cancer: Advances in Cell Signaling and Autophagy Related Mechanisms

Bone metastasis is a frequent complication of breast cancer with nearly 70% of metastatic breast cancer patients developing bone metastasis during the course of their disease. The bone represents a dynamic microenvironment which provides a fertile soil for disseminated tumor cells, however, the mechanisms which regulate the interactions between a metastatic tumor and the bone microenvironment remain poorly understood. Recent studies indicate that during the metastatic process a bidirectional relationship between metastatic tumor cells and the bone microenvironment begins to develop. Metastatic cells display aberrant expression of genes typically reserved for skeletal development and alter the activity of resident cells within the bone microenvironment to promote tumor development, resulting in the severe bone loss. While transcriptional regulation of the metastatic process has been well established, recent findings from our and other research groups highlight the role of the autophagy and secretory pathways in interactions between resident and tumor cells during bone metastatic tumor growth. These reports show high levels of autophagy-related markers, regulatory factors of the autophagy pathway, and autophagy-mediated secretion of matrix metalloproteinases (MMP's), receptor activator of nuclear factor kappa B ligand (RANKL), parathyroid hormone related protein (PTHrP), as well as WNT5A in bone metastatic breast cancer cells. In this review, we discuss the recently elucidated mechanisms and their crosstalk with signaling pathways, and potential therapeutic targets for bone metastatic disease.

Panax notoginseng saponins reduces the cisplatin-induced acute renal injury by increasing HIF-1α/BNIP3 to inhibit mitochondrial apoptosis pathway

Cisplatin (CDDP) may induce apoptosis of renal tubular epithelial cells (RTEC) and cause CDDP-induced acute kidney injury (CAKI) during cancer treatment, but yet lack of preventive measures and effective treatment. As a new Chinese herbal preparation, Panax notoginseng saponins (PNS) has been found to mitigate CDDP-induced CAKI through elevating the expression of HIF-1α in the rat model, according to the data from our previous works. However, the underlying link between HIF-1α and apoptosis has not been well elucidated. The current study as a follow-up work, was aimed to reveal if PNS improves CAKI through HIF-1α-dependent apoptosis. A stably HIF-1α-knockdown human proximal tubular epithelial cell (HK-2) line was established by transfecting a HIF-1α-siRNA into HK-2 cells. Cell viability, mitochondrial function, cell apoptosis ratio and the expression of apoptosis-associated proteins (Cyt C, Bcl2, Bax, caspases 3) were determined. In order to elucidate the underlying mechanism, the expression of HIF-1α and BNIP3 were assessed. Our results showed that treatment of PNS rescued the cell viability of CDDP-injured HK-2 or HIF-1α-knockdown HK-2 cells, and increased the expression levels of ATP and MMP in HK-2 or HIF-1α-knockdown HK-2 cells which were reduced by CDDP. Moreover, PNS treatment decreased the CDDP or CDDP plus HIF-1α-knockdown-induced elevation of apoptosis and apoptosis-associated protein expressions. These findings demonstrate that PNS reduces CAKI through increasing HIF-1α to inhibit mitochondrial apoptosis pathway. Hence, we suggest PNS as a protective and therapeutic new drug for CDDP treatment of cancers, which might have significant meaning of further research and application potential.

The Double-Edge Sword of Autophagy in Cancer: From Tumor Suppression to Pro-tumor Activity

During tumorigenesis, cancer cells are exposed to a wide variety of intrinsic and extrinsic stresses that challenge homeostasis and growth. Cancer cells display activation of distinct mechanisms for adaptation and growth even in the presence of stress. Autophagy is a catabolic mechanism that aides in the degradation of damaged intracellular material and metabolite recycling. This activity helps meet metabolic needs during nutrient deprivation, genotoxic stress, growth factor withdrawal and hypoxia. However, autophagy plays a paradoxical role in tumorigenesis, depending on the stage of tumor development. Early in tumorigenesis, autophagy is a tumor suppressor via degradation of potentially oncogenic molecules. However, in advanced stages, autophagy promotes the survival of tumor cells by ameliorating stress in the microenvironment. These roles of autophagy are intricate due to their interconnection with other distinct cellular pathways. In this review, we present a broad view of the participation of autophagy in distinct phases of tumor development. Moreover, autophagy participation in important cellular processes such as cell death, metabolic reprogramming, metastasis, immune evasion and treatment resistance that all contribute to tumor development, is reviewed. Finally, the contribution of the hypoxic and nutrient deficient tumor microenvironment in regulation of autophagy and these hallmarks for the development of more aggressive tumors is discussed.

Sirtuin6 (SIRT6) Promotes the EMT of Hepatocellular Carcinoma by Stimulating Autophagic Degradation of E-Cadherin

EMT is a pivotal mechanism involved in tumor metastasis, which is the leading cause of poor prognosis for hepatocellular carcinoma (HCC). Sirtuin family members function as NAD⁺-dependent deacetylases that are essential for tumor metastasis and epithelial-mesenchymal transition (EMT). However, no causal association has been established between Sirtuin6 (SIRT6) and HCC metastasis. SIRT6 expression pattern and its association with HCC metastasis were investigated by informatic analysis, and verified by qRT-PCR and immunochemistry in HCC tissues. Transwell assay, qRT-PCR, and immunofluorescence assay were utilized to assess the effects of SIRT6 on metastasis and E-cadherin expression in vitro and in vivo. Immunoprecipitation assay was performed to observe whether SIRT6 deacetylated Beclin-1 in HCC cells. Immunofluorescence assay and inhibitor treatment rescue experiments were used to clarify the mechanism by which SIRT6 facilitated EMT and metastasis. SIRT6 upregulation was quite prevalent in HCC tissues and closely correlated with worse overall survival, disease-relapse free survival, and HCC metastasis. Furthermore, SIRT6 promoted HCC cell migration, invasion, and EMT. Mechanistically, we found that SIRT6 deacetylated Beclin-1 in HCC cells and this event led to the promotion of the autophagic degradation of E-cadherin. Noticeably, E-cadherin degradation and invasion, migration induced by SIRT6 overexpression could be rescued by dual mutation of Beclin-1 (inhibition of acetylation), CQ (autophagy inhibitor), and knockdown of Atg7. In addition, SIRT6 promoted N-cadherin and Vimentin expression via deacetylating FOXO3a in HCC. These results established a relationship between SIRT6 and HCC EMT and further elucidated the mechanisms underlying HCC metastasis, helping provide a promising approach for the treatment of HCC. IMPLICATIONS: Inhibiting SIRT6 represents a potential therapeutic approach to suppress HCC metastasis partially through reduction of autophagic degradation of E-cadherin.

Evaluation of genetic variants in autophagy pathway genes as prognostic biomarkers for breast cancer

Autophagy-related genes (ATGs) play a critical role in the development of various diseases including cancer. However, the role of ATGs in breast cancer survival remains unclear. This study aims to investigate whether genetic variants in core ATGs are correlated with the prognosis of breast cancer. A total of 14 potentially functional variants in core ATGs were genotyped in 790 breast cancer patients. The association of each variant with breast cancer-specific survival was evaluated by log-rank test and Cox regression model. In silico analysis was also performed to evaluate the potential function of selected variants. We found that one variant in ATG7 rs8154 (A>G) was significantly associated with breast cancer-specific survival after adjusted for age and clinical stage (HR=1.61, 95% CI: 1.12-2.31, P=0.010). Stratified analysis showed that the prognostic role of rs8154 was significant in subgroups of elder age, elder menarche age, and postmenopausal status (all P<0.001). Interaction effects were also detected between rs8154 and these grouping variables. In silico analysis revealed that rs8154 was annotated to be expression quantitative trait loci (eQTL) and methylation quantitative trait loci (meQTL) based on Genotype-Tissue Expression (GTEx) and The Cancer Genome Atlas (TCGA) datasets (both P<0.05). In addition, upregulated expression of ATG7 in breast cancer tissues was observed and is significantly associated with poorer overall survival (log-rank P=0.015), poorer relapse free survival (log-rank P=0.017), and poorer distant metastasis free survival (log-rank P=0.034) in different datasets. Summarily, ATG7 variant rs8154 represents a novel prognostic marker for breast cancer patients, which may shed light on clinical risk stratification and therapeutic decision making.

Panax notoginseng saponins mitigate cisplatin induced nephrotoxicity by inducing mitophagy via HIF-1α

We investigated the role of HIF-1α in the mitigation of cisplatin-induced nephrotoxicity by Panax notoginseng saponins (PNS) in a rat model. Serum creatinine (Scr), blood urea nitrogen (BUN) and urinary N-acetyl-β-D-glucosaminidase (NAG) levels were all elevated in cisplatin treated rats. PNS reduced Scr, BUN and NAG levels in the presence or absence of the HIF-1α inhibitor 2-methoxyestradiol (2ME2). PNS also reduced the high tubular injury scores, which corresponded to renal tubular damage in cisplatin-treated rats and which were exacerbated by 2ME2. Renal tissues from PNS-treated rats showed increased HIF-1α mRNA and nuclear localized HIF-1α protein. Moreover, PNS treatment increased BNIP3 mRNA as well as LC3-II, BNIP3 and Beclin-1 proteins and the LC3-II/LC3-I ratio in rat renal tissues. This suggested that PNS treatment enhanced HIF-1α, which in turn increased autophagy. This was confirmed in transmission electron micrographs of renal tissues that showed autophagosomes in PNS-treated renal tissues. These findings demonstrate that PNS mitigates cisplatin-induced nephrotoxicity by enhancing mitophagy via a HIF-1α/BNIP3/Beclin-1 signaling pathway.

Epigenetic regulation of HGF/Met receptor axis is critical for the outgrowth of bone metastasis from breast carcinoma

Our translational research deals with the influence of microenvironment on the phenotype and colonization of bone metastases from breast carcinoma, and on pre-metastatic niche formation. The aim of the present study was to clarify the origin of hepatocyte growth factor (HGF), ligand of Met receptor, the control of the axis HGF/Met by DNA methylation, and its importance for the nexus supportive cells-metastatic cells and for metastasis outgrowth. In bone metastasis of the 1833-xenograft model, DNA methyltransferase blockade using the chemotherapic drug 5-aza-2′-deoxycytidine (decitabine) strongly reduced the expression of HGF/Met receptor axis and of E-cadherin, with decrease of metastasis wideness and osteolysis, prolonging mice survival. Thus, DNA methylation events acted as commanders of breast carcinoma cells metastatizing to bone influencing the epithelial phenotype. HGF emerged as a bone-marrow stimulus, and the exosomes seemed to furnish HGF to metastatic cells. In fact, decitabine treatment similarly affected some markers of these microvesicles and HGF, indicating that its supply to recipient cells was prevented. Notably, in bone metastasis the hypomethylation of HGF, Met and E-cadherin promoters did not appear responsible for their elevated expression, but we suggest the involvement of hypermethylated regulators and of Wwox oncosuppressor, the latter being affected by decitabine. Wwox expression increased under decitabine strongly localizing in nuclei of bone metastases. We hypothesize a role of Wwox in Met activity since in vitro Wwox overexpression downregulated the level of nuclear-Met protein fragment and Met stability, also under long exposure of 1833 cells to decitabine. HGF enhanced phosphoMet and the activity in nuclei, an effect partially prevented by decitabine. Altogether, the data indicated the importance to target the tumor microenvironment by blocking epigenetic mechanisms, which control critical events for colonization such as HGF/Met axis and Wwox, as therapy of bone metastasis.