Nuclear Beclin 1 Destabilizes Retinoblastoma Protein to Promote Cell Cycle Progression and Colorectal Cancer Growth

Pyrrolidine SS13 induces oxidative stress and autophagy-mediated cell death in colorectal cancer cells

INTRODUCTION

Pyrrolidines, nitrogenous organic compounds, are among the most intensively studied agents because of their antibacterial, antiviral, neurological, and promising antitumor effects. Moreover, many medicinal drugs contain pyrrolidine moiety such as sunitinib (anticancer drug), telaprevir and ombitasvir (antiviral drugs) or ramipril (antihypertensive drug).

RATIONALE OF THE STUDY

Based on the pro-apoptotic effect of pyrrolidine SS13, this study focuses on the pro-oxidative properties of the tested pyrrolidine SS13 on colorectal cancer cells to deepen the understanding of its mechanisms of action.

RESEARCH HYPOTHESIS

We hypothesize that SS13 induces oxidative stress and autophagy activation in HCT116 and Caco-2 cell lines, thus contributing to antiproliferative effects.

METHODS

Flow cytometry, western blot, fluorescence microscopy and qRT-PCR were used to evaluate the effect of pyrrolidine SS13.

CONCLUSION AND FUTURE DIRECTIONS

Pyrrolidine SS13 induced oxidative stress through the accumulation of reactive oxygen and nitrogen species in both cell lines and the modulation of both superoxide dismutase isoenzymes (SOD1, SOD2). Oxidative stress was also associated with the activation of DNA damage response system and modulation of stress/survival pathways. We demonstrated for the first time that pyrrolidine SS13 is involved in the induction of autophagy accompanied by increased levels of autophagic markers (p-AMPK, p-ULK, LC3I/II and ATG7) and a significant decrease in p62 protein levels in both cell lines. Finally, chloroquine, an inhibitor of autophagy, enhanced cell survival and suppressed the cytotoxic effect of SS13 in HCT116 and Caco-2 cells, indicating that SS13 contributes to autophagy-mediated cell death. Taken together, our results suggest that oxidative stress and autophagy participate in the antiproliferative effect of pyrrolidine SS13 on colorectal cancer cells. Further research using primary cell cultures obtained from different animal tissues as well as performing in vivo experiments is needed to understand these processes in detail and to investigate the potential therapeutic application of new pyrrolidine derivatives.

VHL suppresses autophagy and tumor growth through PHD1-dependent Beclin1 hydroxylation

The Von Hippel-Lindau (VHL) protein, which is frequently mutated in clear-cell renal cell carcinoma (ccRCC), is a master regulator of hypoxia-inducible factor (HIF) that is involved in oxidative stresses. However, whether VHL possesses HIF-independent tumor-suppressing activity remains largely unclear. Here, we demonstrate that VHL suppresses nutrient stress-induced autophagy, and its deficiency in sporadic ccRCC specimens is linked to substantially elevated levels of autophagy and correlates with poorer patient prognosis. Mechanistically, VHL directly binds to the autophagy regulator Beclin1, after its PHD1-mediated hydroxylation on Pro54. This binding inhibits the association of Beclin1-VPS34 complexes with ATG14L, thereby inhibiting autophagy initiation in response to nutrient deficiency. Expression of non-hydroxylatable Beclin1 P54A abrogates VHL-mediated autophagy inhibition and significantly reduces the tumor-suppressing effect of VHL. In addition, Beclin1 P54-OH levels are inversely correlated with autophagy levels in wild-type VHL-expressing human ccRCC specimens, and with poor patient prognosis. Furthermore, combined treatment of VHL-deficient mouse tumors with autophagy inhibitors and HIF2α inhibitors suppresses tumor growth. These findings reveal an unexpected mechanism by which VHL suppresses tumor growth, and suggest a potential treatment for ccRCC through combined inhibition of both autophagy and HIF2α.

The Role of Beclin 1 and HER2 in Colorectal Carcinoma; An Immunohistochemical Study

OBJECTIVE

This study aimed to evaluate the expression of Beclin 1 and HER2 proteins using immunohistochemistry in CRC tissues compared to colonic adenoma, and to investigate the correlation of their expression with clinicopathological parameters and survival outcomes in CRC patients.

METHODS

The study utilized paraffin-embedded blocks from 17 colonic adenoma and 81 CRC cases. Immunohistochemical analysis was performed to assess the expression of Beclin 1 and HER2 proteins.

RESULTS

The cytoplasmic expression of Beclin 1 was significantly higher in CRC tissues compared to adenoma specimens (P=0.051). High Beclin 1 expression was significantly associated with distal colon location (P=0.028). High HER2 cytoplasmic expression was significantly associated with vascular invasion (P=0.05), perineural invasion (P=0.03), and shorter overall survival (P=0.035).

CONCLUSIONS

The findings suggest that Beclin 1 plays a role in colorectal carcinogenesis, with higher expression observed in CRC cases compared to adenoma cases.  Furthermore, HER2 carries poor prognostic impact in CRC cases.

Targeting autophagy and beyond: Deconvoluting the complexity of Beclin-1 from biological function to cancer therapy

Beclin-1 is the firstly-identified mammalian protein of the autophagy machinery, which functions as a molecular scaffold for the assembly of PI3KC3 (class III phosphatidylinositol 3 kinase) complex, thus controlling autophagy induction and other cellular trafficking events. Notably, there is mounting evidence establishing the implications of Beclin-1 in diverse tumorigenesis processes, including tumor suppression and progression as well as resistance to cancer therapeutics and CSC (cancer stem-like cell) maintenance. More importantly, Beclin-1 has been confirmed as a potential target for the treatment of multiple cancers. In this review, we provide a comprehensive survey of the structure, functions, and regulations of Beclin-1, and we discuss recent advances in understanding the controversial roles of Beclin-1 in oncology. Moreover, we focus on summarizing the targeted Beclin-1-regulating strategies in cancer therapy, providing novel insights into a promising strategy for regulating Beclin-1 to improve cancer therapeutics in the future.

Interaction mechanisms between autophagy and ferroptosis: Potential role in colorectal cancer

Colorectal cancer (CRC) is a common malignancy that has the second highest incidence and mortality rate. Although there are many personalized treatment options for CRC, the therapeutic effects are ultimately limited by drug resistance. Studies have aimed to block the initiation and progression of CRC by inducing cell death to overcome this obstacle. Substantial evidence has indicated that both autophagy and ferroptosis play important regulatory roles in CRC. Autophagy, a lysosome-dependent process by which cellular proteins and organelles are degraded, is the basic mechanism for maintaining cell homeostasis. The duality and complexity of autophagy in cancer therapy is a hot topic of discussion. Ferroptosis, a regulated cell death pathway, is associated with iron accumulation-induced lipid peroxidation. The activation of ferroptosis can suppress CRC proliferation, invasion and drug resistance. Furthermore, recent studies have suggested an interaction between autophagy and ferroptosis. Autophagy can selectively degrade certain cellular contents to provide raw materials for ferroptosis, ultimately achieving antitumor and anti-drug resistance. Therefore, exploring the interaction between autophagy and ferroptosis could reveal novel ideas for the treatment of CRC. In this review, we describe the mechanisms of autophagy and ferroptosis, focusing on their roles in CRC and the crosstalk between them.

Transcription of Autophagy Associated Gene Expression as Possible Predictors of a Colorectal Cancer Prognosis

(1) Background: Autophagy plays a dual role in oncogenesis-it contributes to the growth of the tumor and can inhibit its development. The aim of this study was to assess changes in the transcriptional activity of LAMP-2, BECN1, PINK1, and FOXO1 genes involved in the autophagy process in histopathologically confirmed adenocarcinoma sections of colorectal cancer: (2) Methods: A gene expression profile analysis was performed using HG-U133A and the RT-qPCR reaction. The transcriptional activity of genes was compared in sections of colorectal cancer in the four clinical stages (CSI-CSIV) concerning the control group; (3) Results: In CSI, the transcriptional activity of the PINK1 gene is highest; in CS II, the LAMP-2 gene is highest, while FOXO1 increases gradually from CSI reaching a maximum in CSIII. There is no BECN1 gene expression in colorectal cancer cells; (4) Conclusions: The observed differences in the mRNA concentration profile of autophagy-related genes in colon cancer specimens may indicate the role of autophagy in the pathogenesis of this cancer. Genes involved in autophagy may be diagnostic tools for colorectal cancer screening and personalized therapy in the future.