Hypoxia and expression of the proapoptotic regulator BNIP3 in cervical cancer

Rapamycin as a Potential Alternative Drug for Squamous Cell Gingiva Carcinoma (Ca9-22): A Focus on Cell Cycle, Apoptosis and Autophagy Genetic Profile

Oral cancer is considered as one of the most common malignancies worldwide. Its conventional treatment primarily involves surgery with or without postoperative adjuvant therapy. The targeting of signaling pathways implicated in tumorigenesis is becoming increasingly prevalent in the development of new anticancer drug candidates. Based on our recently published data, Rapamycin, an inhibitor of the mTOR pathway, exhibits selective antitumor activity in oral cancer by inhibiting cell proliferation and inducing cancer cell apoptosis, autophagy, and cellular stress. In the present study, our focus is on elucidating the genetic determinants of Rapamycin's action and the interaction networks accountable for tumorigenesis suppression. To achieve this, gingival carcinoma cell lines (Ca9-22) were exposed to Rapamycin at IC50 (10 µM) for 24 h. Subsequently, we investigated the genetic profiles related to the cell cycle, apoptosis, and autophagy, as well as gene-gene interactions, using QPCR arrays and the Gene MANIA website. Overall, our results showed that Rapamycin at 10 µM significantly inhibits the growth of Ca9-22 cells after 24 h of treatment by around 50% by suppression of key modulators in the G2/M transition, namely, Survivin and CDK5RAP1. The combination of Rapamycin with Cisplatin potentializes the inhibition of Ca9-22 cell proliferation. A P1/Annexin-V assay was performed to evaluate the effect of Rapamycin on cell apoptosis. The results obtained confirm our previous findings in which Rapamycin at 10 μM induces a strong apoptosis of Ca9-22 cells. The live cells decreased, and the late apoptotic cells increased when the cells were treated by Rapamycin. To identify the genes responsible for cell apoptosis induced by Rapamycin, we performed the RT2 Profiler PCR Arrays for 84 apoptotic genes. The blocked cells were believed to be directed towards cell death, confirmed by the downregulation of apoptosis inhibitors involved in both the extrinsic and intrinsic pathways, including BIRC5, BNIP3, CD40LG, DAPK1, LTA, TNFRSF21 and TP73. The observed effects of Rapamycin on tumor suppression are likely to involve the autophagy process, evidenced by the inhibition of autophagy modulators (TGFβ1, RGS19 and AKT1), autophagosome biogenesis components (AMBRA1, ATG9B and TMEM74) and autophagy byproducts (APP). Identifying gene-gene interaction (GGI) networks provided a comprehensive view of the drug's mechanism and connected the studied tumorigenesis processes to potential functional interactions of various kinds (physical interaction, co-expression, genetic interactions etc.). In conclusion, Rapamycin shows promise as a clinical agent for managing Ca9-22 gingiva carcinoma cells.

Mitophagy: A novel perspective for insighting into cancer and cancer treatment

BACKGROUND

Mitophagy refers to the selective self-elimination of mitochondria under damaged or certain developmental conditions. As an important regulatory mechanism to remove damaged mitochondria and maintain the internal and external cellular balance, mitophagy plays pivotal roles in carcinogenesis and progression as well as treatment.

MATERIALS AND METHODS

Here, we combined data from recent years to comprehensively describe the regulatory mechanisms of mitophagy and its multifaceted significance in cancer, and discusse the potential of targeted mitophagy as a cancer treatment strategy.

RESULTS

The molecular mechanisms regulating mitophagy are complex, diverse, and cross-talk. Inducing or blocking mitophagy has the same or completely different effects in different cancer contexts. Mitophagy plays an indispensable role in regulating cancer metabolic reprogramming, cell stemness, and chemotherapy resistance for better adaptation to tumor microenvironment. In cancer cell biology, mitophagy is considered to be a double-edged sword. And to fully understand the role of mitophagy in cancer development can provide new targets for cancer treatment in clinical practice.

CONCLUSIONS

This review synthesizes a large body of data to comprehensively describe the molecular mechanisms of mitophagy and its multidimensional significance in cancer and cancer treatment, which will undoubtedly deepen the understanding of mitophagy.

Frequent promoter hypermethylation and down regulation of BNIP3: An early event during gallbladder cancer progression

BACKGROUND

Epigenetic alterations have been reported as one of the risk factors of gallbladder cancer. Promoter hypermethylation is associated with high incidence and poor prognosis of GBC. Bcl-2/adenovirus E1B 19 kDa interacting protein 3 is a pro-apoptotic protein member of Bcl-2 family.

AIMS

Present study was aimed to investigate expression profile and promoter methylation status of BNIP3 in GBC and its correlation with clinico-pathological parameters.

METHODS

The expression analysis and methylation status of BNIP3 was performed by semi-quantitative reverse transcription polymerase chain reaction and Methylation-specific polymerase chain reaction respectively in 84 GBC patients and 29 gallstone tissues (used as normal controls).

RESULTS

We demonstrate down regulation of BNIP3 in 56% of the GBC samples. BNIP3 promoter is also frequently hypermethylated (69%) in GBC samples. Interestingly, we found that 69% (40/58) of the BNIP3 promoter hypermethylated samples had also reduced expression of BNIP3. Our data demonstrate significant correlation of the mRNA expression and promoter hypermethylation with late stage and nodal metastasis. Hypermethylation of BNIP3 promoter is associated with low overall survival period.

CONCLUSION

Our results suggest that promoter hypermethylation is an early event and can be a frequent mechanism for downregulation of BNIP3 in GBC.

Bcl-2 interacting protein 3 (BNIP3) promotes tumor growth in breast cancer under hypoxic conditions through an autophagy-dependent pathway

Hypoxia-induced autophagy has been implicated in many cancers. Bcl-2 interacting protein 3 (BNIP3) has been associated with hypoxia, whose aberrant expression is involved in the carcinogenesis of breast cancer (BC). Here, we aim to investigate the role of hypoxia-induced autophagy and the mechanistic actions of the bioinformatically identified BNIP3 in BC. The expression pattern of BNIP3 in BC tissues and cell lines was examined using RT-qPCR and Western blot analyses. The binding affinity among BNIP3, BECN1 and BCL-2 was characterized by co-immunoprecipitation. BNIP3 expression was manipulated to assess its effects on BC cell malignant phenotypes, evaluated by cell counting kit-8, Transwell and wound healing assays, and on BC autophagy under hypoxic conditions. A BC tumor xenografts mouse model was further established to substantiate in vitro findings. Up-regulated expression of BNIP3 was found in BC tissues and cell lines, and BNIP3 expression was positively correlated with hypoxia exposure duration. BNIP3 knockdown restricted BC cell proliferation, invasion, and migration under hypoxic conditions. BNIP3 activated BC cell autophagy by inhibiting the binding between BCL-2 and BECN1 under hypoxic conditions. BNIP3-induced autophagy activation enhanced malignant phenotypes of BC cells, thus accelerating the tumorigenesis of BC cells in vivo. These data collectively supported the tumor-promoting role of BNIP3 in autophagy activation of BC under hypoxic conditions, highlighting a potential therapeutic target against BC.

Mitochondria autophagy: a potential target for cancer therapy

Mitophagy is a selective form of macroautophagy in which dysfunctional and damaged mitochondria can be efficiently degraded, removed and recycled through autophagy. Selective removal of damaged or fragmented mitochondria is critical to the functional integrity of the entire mitochondrial network and cells. In past decades, numerous studies have shown that mitophagy is involved in various diseases; however, since the dual role of mitophagy in tumour development, mitophagy role in tumour is controversial, and further elucidation is needed. That is, although mitophagy has been demonstrated to contribute to carcinogenesis, cell migration, ferroptosis inhibition, cancer stemness maintenance, tumour immune escape, drug resistance, etc. during cancer progression, many research also shows that to promote cancer cell death, mitophagy can be induced physiologically or pharmacologically to maintain normal cellular metabolism and prevent cell stress responses and genome damage by diminishing mitochondrial damage, thus suppressing tumour development accompanying these changes. Signalling pathway-specific molecular mechanisms are currently of great biological significance in the identification of potential therapeutic targets. Here, we review recent progress of molecular pathways mediating mitophagy including both canonical pathways (Parkin/PINK1- and FUNDC1-mediated mitophagy) and noncanonical pathways (FKBP8-, Nrf2-, and DRP1-mediated mitophagy); and the regulation of these pathways, and abovementioned pro-cancer and pro-death roles of mitophagy. Finally, we summarise the role of mitophagy in cancer therapy. Mitophagy can potentially be acted as the target for cancer therapy by promotion or inhibition.

BNIP3 in Lung Cancer: To Kill or Rescue?

Simple Summary

Bcl-2/adenovirus E1B 19kDa interacting protein 3 (BNIP3) is a pro-apoptotic BH3-only protein of the Bcl-2 family. Its function in various biological processes was described. Although potential involvement of BNIP3 in cancer progression has been discussed in many review articles, its specific role in lung cancer is still unclear. In this review, we shed light on the BNIP3‘s role in different types of cancer in general and lung cancer, in particular, as well as suggested its potential for targeting therapy of lung cancer.

Abstract

Bcl-2/adenovirus E1B 19kDa interacting protein 3 (BNIP3) is a pro-apoptotic BH3-only protein of the Bcl-2 family. Initially, BNIP3 was described as one of the mediators of hypoxia-induced apoptotic cell death in cardiac myocytes and neurons. Besides apoptosis, BNIP3 plays a crucial role in autophagy, metabolic pathways, and metastasis-related processes in different tumor types. Lung cancer is one of the most aggressive types of cancer, which is often diagnosed at an advanced stage. Therefore, there is still urgent demand for reliable biochemical markers for lung cancer and its efficient treatment. Mitochondria functioning and mitochondrial proteins, including BNIP3, have a strong impact on lung cancer development and progression. Here, we summarized current knowledge about the BNIP3 gene and protein features and their role in cancer progression, especially in lung cancer in order to develop new therapeutic approaches associated with BNIP3.

Mitophagy in Cancer: A Tale of Adaptation

：In the past years, we have learnt that tumors co-evolve with their microenvironment, and that the active interaction between cancer cells and stromal cells plays a pivotal role in cancer initiation, progression and treatment response. Among the players involved, the pathways regulating mitochondrial functions have been shown to be crucial for both cancer and stromal cells. This is perhaps not surprising, considering that mitochondria in both cancerous and non-cancerous cells are decisive for vital metabolic and bioenergetic functions and to elicit cell death. The central part played by mitochondria also implies the existence of stringent mitochondrial quality control mechanisms, where a specialized autophagy pathway (mitophagy) ensures the selective removal of damaged or dysfunctional mitochondria. Although the molecular underpinnings of mitophagy regulation in mammalian cells remain incomplete, it is becoming clear that mitophagy pathways are intricately linked to the metabolic rewiring of cancer cells to support the high bioenergetic demand of the tumor. In this review, after a brief introduction of the main mitophagy regulators operating in mammalian cells, we discuss emerging cell autonomous roles of mitochondria quality control in cancer onset and progression. We also discuss the relevance of mitophagy in the cellular crosstalk with the tumor microenvironment and in anti-cancer therapy responses.

BNIP3 acts as transcriptional repressor of death receptor-5 expression and prevents TRAIL-induced cell death in gliomas

Glioblastoma multiforme (GBM) is the most common and malignant brain tumor, and current treatment modalities such as surgical resection, adjuvant radiotherapy and temozolomide (TMZ) chemotherapy are ineffective. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a novel cancer therapeutic agent for GBM because of its capability of inducing apoptosis in glioma cells. Unfortunately, the majority of glioma cells are resistant to TRAIL-induced apoptosis. The Bcl-2 nineteen kilodalton interacting protein (BNIP3) is a pro-cell death BH3-only member of the Bcl-2 family that is one of the highest expressed genes in hypoxic regions of GBM tumors. We previously found that BNIP3 is localized to the nucleus in GBM tumors and suppresses cell death in glioma cells. Herein, we have discovered when BNIP3 nuclear expression is knockdown in glioma cell lines and in normal mouse astrocytes, TRAIL and its death receptor, death receptor-5 (DR5) expression is increased. In addition, when nuclear BNIP3 expression is increased, the amount of TRAIL-induced apoptosis is reduced. Using a streptavidin pull-down assay, we found that BNIP3 binds to the DR5 promoter and nuclear BNIP3 binds to the DR5 promoter. Furthermore, nuclear BNIP3 expression in GBM tumors correlates with decreased DR5 expression. Taken together, we have discovered a novel transcriptional repression function for BNIP3 conferring a TRAIL resistance in glioma cells.

Modulation of serines 17 and 24 in the LC3-interacting region of Bnip3 determines pro-survival mitophagy versus apoptosis

BH3-only proteins integrate apoptosis and autophagy pathways, yet regulation and functional consequences of pathway cross-talk are not fully resolved. The BH3-only protein Bnip3 is an autophagy receptor that signals autophagic degradation of mitochondria (mitophagy) via interaction of its LC3-interacting region (LIR) with Atg8 proteins. Here we report that phosphorylation of serine residues 17 and 24 flanking the Bnip3 LIR promotes binding to specific Atg8 members LC3B and GATE-16. Using quantitative multispectral image-based flow cytometry, we demonstrate that enhancing Bnip3-Atg8 interactions via phosphorylation-mimicked LIR mutations increased mitochondrial sequestration, lysosomal delivery, and degradation. Importantly, mitochondria were targeted by mitophagy prior to cytochrome c release, resulting in reduced cellular cytochrome c release capacity. Intriguingly, pro-survival Bcl-x(L) positively regulated Bnip3 binding to LC3B, sequestration, and mitochondrial autophagy, further supporting an anti-apoptotic role for Bnip3-induced mitophagy. The ensemble of these results demonstrates that the phosphorylation state of the Bnip3 LIR signals either the induction of apoptosis or pro-survival mitophagy.

MicroRNA145 targets BNIP3 and suppresses prostate cancer progression

The putative tumor suppressor miR145 is transcriptionally regulated by TP53 and is downregulated in many tumors; however, its role in prostate cancer is unknown. On the other hand, BCL2/adenovirus E1B 19-kDa interacting protein 3 (BNIP3) is overexpressed in various tumors, including prostate cancer, and may transcriptionally repress the apoptosis-inducing factor (AIF) gene. Although BNIP3 transcription is controlled by hypoxia-inducible factor 1alpha (also elevated in prostate cancer), we postulated the posttranscriptional regulation of BNIP3 by miR145 through bioinformatics analysis, and herein we experimentally showed that miR145 negatively regulated BNIP3 by targeting its 3'-untranslated region. Artificial overexpression of miR145 by using adenoviral vectors in prostate cancer PC-3 and DU145 cells significantly downregulated BNIP3, together with the upregulation of AIF, reduced cell growth, and increased cell death. Artificial overexpression of wild-type TP53 in PC-3 cells (which lack TP53 protein) and DU145 cells (in which mutated nonfunctioning TP53 is expressed) significantly upregulated miR145 expression with consequent effects on BNIP3 and cell behavior as with miR145 overexpression. Analysis of prostate cancer (n = 134) and benign prostate (n = 83) tissue sample showed significantly decreased miR145 and increased BNIP3 expression in prostate cancer (P < 0.001), particularly in those with tumor progression, and both molecular changes were associated with unfavorable outcome. Abnormalities of the miR145-BNIP3 pair as part of TP53-miR145-BNIP3-AIF network may play a major role in prostate cancer pathogenesis and progression.

The role of Bcl-2 family member BNIP3 in cell death and disease: NIPping at the heels of cell death

Bcl-2 nineteen-kilodalton interacting protein (BNIP3) is a BH-3-only Bcl-2 family member whose expression levels increase during stress such as hypoxia through hypoxia-inducing factor-1-dependent or -independent mechanisms. When BNIP3 expression is induced, it localizes to the mitochondria and triggers a loss of membrane potential, and an increase in the reactive oxygen species production, which often leads to cell death. Cells under normal growth conditions suppress BNIP3 expression through transcriptional repression. There is considerable debate in the literature regarding what type of cell death is induced by BNIP3. It has been observed that BNIP3 could induce necrosis, autophagy and/or apoptosis. In contrast, other studies indicate that BNIP3 could promote cell survival. Besides its cell death regulation, BNIP3 plays a key role in the pathogenicity of many diseases. In cardiac infarction, loss of BNIP3 expression has been shown to reduce the number of damaged cardiomyocytes after ischemia and reperfusion. BNIP3 expression also plays an important role in the deregulation of cell death in many cancers. In this review, we will discuss the different and often contradictory mechanisms of BNIP3 regulation of cell death and the role that BNIP3 may play in diseases.