Radiation-Induced Autophagy in Human Pancreatic Cancer Cells is Critically Dependent on G2 Checkpoint Activation: A Mechanism of Radioresistance in Pancreatic Cancer

Moving From the Background Toward the Spotlight: A Critical Review of Radiation Therapy for Locally Advanced Pancreas Cancer

Radiation therapy (RT) for locally advanced pancreatic cancer (LAPC) continues to be controversial. Advances in both systemic therapy and RT techniques have changed the landscape of LAPC management in recent years. Clinical outcomes of ablative RT have been encouraging, and randomized clinical trials may clarify the role of RT for LAPC. We present a contemporary critical review of key aspects regarding optimal patient selection, radiation dose escalation techniques, novel radiosensitizers and radioprotectors, and treatment response assessment for LAPC.

Autophagy related proteins as potential biomarkers in predicting cancer prognosis after chemoradiotherapy: systematic review and meta-analysis

BACKGROUND

Resistance to chemo- and radiotherapy is the main obstacle in cancer treatment success, which results in cancer's poor prognosis. Therefore finding the exact mechanism of resistance may contribute to addressing this concern. This could result in improved cancer prognosis and survival outcomes for cancer patients by targeting the basic causes of resistance.

AIM

This systematic review and meta-analysis assessed the potential of using autophagy-related proteins as prognostic biomarkers in radiotherapy-treated patients.

METHODS

Following PRISMA guidelines, we systematically reviewed 956 studies from PubMed, Scopus, and Web of Science databases until April 2023. The keywords used for this purpose were 'cancer', 'radiotherapy', 'prognosis', and 'Autophagy'. Then the related meta-analysis was performed using STATA software.

RESULTS

Four studies met the inclusion criteria. Upregulation of autophagy markers (LC3B, Beclin1 and ULK1) and subsequent activation of autophagy were significantly associated with a higher risk of mortality (1.95 times) in radiotherapy-treated groups compared with patients with low expression of these markers. Although such results were observed for recurrence-free survival (RFS); however, it was not significant.

CONCLUSION

The findings of this meta-analysis suggest that autophagy activation may be a critical factor in resistance to radiotherapy and subsequent poor survival rates in cancer patients. Consequently, assessing the expression of autophagy-related markers like Beclin1, LC3II, P62, and ULK may be a useful method for monitoring cancer prognosis following radiotherapy.

A Dual-Channel Ca2+ Nanomodulator Induces Intracellular Ca2+ Disorders via Endogenous Ca2+ Redistribution for Tumor Radiosensitization

Tumor cells harness Ca2+ to maintain cellular homeostasis and withstand external stresses from various treatments. Here, a dual-channel Ca2+ nanomodulator (CAP-P-NO) is constructed that can induce irreversible intracellular Ca2+ disorders via the redistribution of tumor-inherent Ca2+ for disrupting cellular homeostasis and thus improving tumor radiosensitivity. Stimulated by tumor-overexpressed acid and glutathione, capsaicin and nitric oxide are successively escaped from CAP-P-NO to activate the transient receptor potential cation channel subfamily V member 1 and the ryanodine receptor for the influx of extracellular Ca2+ and the release of Ca2+ in the endoplasmic reticulum, respectively. The overwhelming level of Ca2+ in tumor cells not only impairs the function of organelles but also induces widespread changes in the gene transcriptome, including the downregulation of a set of radioresistance-associated genes. Combining CAP-P-NO treatment with radiotherapy achieves a significant suppression against both pancreatic and patient-derived hepatic tumors with negligible side effects. Together, the study provides a feasible approach for inducing tumor-specific intracellular Ca2+ overload via endogenous Ca2+ redistribution and demonstrates the great potential of Ca2+ disorder therapy in enhancing the sensitivity for tumor radiotherapy.

Differential Sensitivity to Ionizing Radiation in Gemcitabine-Resistant and Paclitaxel-Resistant Pancreatic Cancer Cells

PURPOSE

Chemoresistance remains a major challenge in treating pancreatic ductal adenocarcinoma (PDAC). Although chemoradiation has proven effective in other tumor types, such as head and neck squamous cell carcinoma, its role in PDAC and effect on acquired chemoresistance have yet to be fully explored. In this study, we investigated the sensitivity of gemcitabine-resistant (GR) and paclitaxel-resistant (PR) PDAC cells to ionizing radiation (IR) and their underlying mechanisms.

METHODS AND MATERIALS

GR and PR clones were generated from PANC-1, PATU-T, and SUIT2-007 pancreatic cancer cell lines. Cell survival after radiation was assessed using clonogenic assay, sulforhodamine B assay, apoptosis, and spheroid growth by bioluminescence. Radiation-induced DNA damage was assessed using Western blot, extra-long polymerase chain reaction, reactive oxygen species production, and immunofluorescence. Autophagy and modulation of the Hippo signaling pathway were investigated using proteomics, Western blot, immunofluorescence, and reverse-transcription quantitative polymerase chain reaction.

RESULTS

In both 2- and 3-dimensional settings, PR cells were more sensitive to IR and showed decreased β-globin amplification, indicating more DNA damage accumulation compared with GR or wild-type cells after 24 hours. Proteomic analysis of PR PATU-T cells revealed that the protein MST4, a kinase involved in autophagy and the Hippo signaling pathway, was highly downregulated. A differential association was found between autophagy and radiation treatment depending on the cell model. Interestingly, increased yes-associated protein nuclear localization and downstream Hippo signaling pathway target gene expression were observed in response to IR.

CONCLUSIONS

This was the first study investigating the potential of IR in targeting PDAC cells with acquired chemoresistance. Our results demonstrate that PR cells exhibit enhanced sensitivity to IR due to greater accumulation of DNA damage. Additionally, depending on the specific cellular context, radiation-induced modulation of autophagy and the Hippo signaling pathway emerged as potential underlying mechanisms, findings with potential to inform personalized treatment strategies for patients with acquired chemoresistance.

Circular RNAs in pancreatic cancer progression

Pancreatic cancer (PC), typically diagnosed at relatively advanced stages with poor prognosis, is a dominant cause of cancer-related deaths worldwide. Accumulating evidence demonstrates that circular RNAs (circRNAs) are abnormally expressed in diverse tumors and affect tumorigenesis and progression. In this article, we examine the roles of circRNAs in regulation of PC progression. Additionally, circRNAs enriched in exosomes could be transferred among PC cells to modulate malignancy. Characterization of regulatory mechanisms involving circRNAs in general and PC specifically will enable earlier detection and potential development of therapeutic strategies.

A bioinformatics analysis, pre-clinical and clinical conception of autophagy in pancreatic cancer: Complexity and simplicity in crosstalk

Pancreatic cancer (PC) is a serious gastrointestinal tract disease for which the 5-year survival rate is less than 10%, even in developed countries such as the USA. The genomic profile alterations and dysregulated biological mechanisms commonly occur in PC. Macroautophagy/autophagy is a cell death process that is maintained at a basal level in physiological conditions, whereas its level often changes during tumorigenesis. The function of autophagy in human cancers is dual and can be oncogenic and onco-suppressor. Autophagy is a potent controller of tumorigenesis in PC. The supportive autophagy in PC escalates the growth rate of PC cells and its suppression can mediate cell death. Autophagy also determines the metastasis of PC cells, and it can control the EMT in affecting migration. Moreover, starvation and hypoxia can stimulate glycolysis, and glycolysis induction can be mediated by autophagy in enhancing tumorigenesis in PC. Furthermore, protective autophagy stimulates drug resistance and gemcitabine resistance in PC cells, and its inhibition can enhance radiosensitivity. Autophagy can degrade MHC-I to mediate immune evasion and also regulates polarization of macrophages in the tumor microenvironment. Modulation of autophagy activity is provided by silibinin, ursolic acid, chrysin and huaier in the treatment of PC. Non-coding RNAs are also controllers of autophagy in PC and its inhibition can improve therapy response in patients. Moreover, mitophagy shows dysregulation in PC, which can enhance the proliferation of PC cells. Therefore, a bioinformatics analysis demonstrates the dysregulation of autophagy-related proteins and genes in PC as biomarkers.

Regulation of pancreatic cancer therapy resistance by chemokines

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy characterized by high resistance and poor response to chemotherapy. In addition, the poorly immunogenic pancreatic tumors constitute an immunosuppressive tumor microenvironment (TME) that render immunotherapy-based approaches ineffective. Understanding the mechanisms of therapy resistance, identifying new targets, and developing effective strategies to overcome resistance can significantly impact the management of PDAC patients. Chemokines are small soluble factors that are significantly deregulated during PDAC pathogenesis, contributing to tumor growth, metastasis, immune cell trafficking, and therapy resistance. Thus far, different chemokine pathways have been explored as therapeutic targets in PDAC, with some promising results in recent clinical trials. Particularly, immunotherapies such as immune check point blockade therapies and CAR-T cell therapies have shown promising results when combined with chemokine targeted therapies. Considering the emerging pathological and clinical significance of chemokines in PDAC, we reviewed major chemokine-regulated pathways leading to therapy resistance and the ongoing endeavors to target chemokine signaling in PDAC. This review discusses the role of chemokines in regulating therapy resistance in PDAC and highlights the continuing efforts to target chemokine-regulated pathways to improve the efficacy of various treatment modalities.

The role of radiotherapy-related autophagy genes in the prognosis and immune infiltration in lung adenocarcinoma

Background

There is a close relationship between radiotherapy and autophagy in tumors, but the prognostic role of radiotherapy-related autophagy genes (RRAGs) in lung adenocarcinoma (LUAD) remains unclear.

Methods

Data used in the current study were extracted from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Weighted gene co-expression network analysis (WGCNA) was executed to recognize module genes associated with radiotherapy. The differentially expressed genes (DEGs) between different radiotherapy response groups were filtered via edgeR package. The differentially expressed radiotherapy-related autophagy genes (DERRAGs) were obtained by overlapping the module genes, DEGs, and autophagy genes (ATGs). Then, prognostic autophagy genes were selected by Cox analyses, and a risk model and nomogram were subsequently built. Gene Set Enrichment Analysis (GSEA) and single-sample Gene Set Enrichment Analysis (ssGSEA) were performed to investigate potential mechanisms through which prognostic autophagy signatures regulate LUAD. Radiotherapy-resistant cell lines (A549IR and PC9IR) were established after exposure to hypo-fractionated irradiation. Ultimately, mRNA expression was validated by quantitative real-time PCR (qRT-PCR), and relative protein levels were measured in different cell lines by western blot.

Results

A total of 11 DERRAGs were identified in LUAD. After Cox analyses, SHC1, NAPSA, and AURKA were filtered as prognostic signatures in LUAD. Then, the risk score model was constructed using the prognostic signatures, which had a good performance in predicting the prognosis, as evidenced by receiver operating characteristics curves. Furthermore, Cox regression analyses demonstrated that risk score was deemed as an independent prognostic factor in LUAD. Moreover, GSEA and ssGSEA results revealed that prognostic RRAGs may regulate LUAD by modulating the immune microenvironment and affecting cell proliferation. The colony formation assay showed that the radiosensitivity of radiation-resistant cell lines was lower than that of primary cells. The western blot assay found that the levels of autophagy were elevated in the radiotherapy-resistant cell lines. Moreover, the expression of DERRAGs (SHC1, AURKA) was higher in the radiotherapy-resistant cells than in primary cells.

Conclusion

Our study explored the role of RRAGs in the prognosis of LUAD and identified three biomarkers. The findings enhanced the understanding of the relationship between radiotherapy, autophagy, and prognosis in LUAD and provided potential therapeutic targets for LUAD patients.

Enhanced autophagy promotes radiosensitivity by mediating Sirt1 downregulation in RM-1 prostate cancer cells

Autophagy is a double-edged sword that affects tumor progression by promoting cell survival or death depending on different living contexts. The concrete mechanism by which autophagy modulates the efficacy of radiotherapy for prostate cancer (PC) remains unclear. We exposed RM-1 PC cells to X-ray and explored the role of autophagy in radiation injury. Our results showed increased apoptosis and autophagy levels in RM-1 cells after radiation. Pharmacological inhibition of autophagy by chloroquine significantly mitigated radiation-induced apoptosis, while the enhancement of autophagy by rapamycin aggravated apoptosis. Sirt1, a member of sirtuin family, deacetylates various transcription factors to trigger cell survival in response to radiation injury. We found that radiation led to Sirt1 downregulation, which was reversed by the inhibition of autophagy. On the contrary, enhanced autophagy further diminished protein level of Sirt1. Notably, overexpression of Sirt1 by plasmid significantly alleviated radiation-induced apoptosis, but silenced Sirt1 by siRNA further induced apoptosis, indicating the radioprotective effect of Sirt1 on RM-1 cells. In summary, our findings suggested that autophagy-mediated Sirt1 downregulation might be a promising therapeutic target for PC.

Long non-coding RNA PTPRG-AS1/microRNA-124-3p regulates radiosensitivity of nasopharyngeal carcinoma via the LIM Homeobox 2-dependent Notch pathway through competitive endogenous RNA mechanism

Nasopharyngeal carcinoma (NPC) is a malignant tumor in the nasopharyngeal cavity. LncRNA PTPRG-AS1 is essential in NPC radiosensitivity. This study sought to explore the mechanism of PTPRG-AS1 in NPC radiosensitivity by regulating the miR-124-3p/LHX2 axis. First, NPC-related microarray was analyzed to screen differentially expressed lncRNAs. PTPRG-AS1 and miR-124-3p expression patterns in NPC tissues and adjacent tissues of NPC patients and NPC cell lines were detected by RT-qPCR. PTPRG-AS1 was knocked down in CNE2 and 5–8 F cells by transfection. The radiosensitivity, proliferation and apoptosis before and after radiotherapy (0/6 Gy) were detected by cloning formation assay, CCK-8 assay, and flow cytometry. Bioinformatics, Pearson correlation analysis, RNA pull-down, and luciferase reporter assays were performed to explore the regulatory relationship of the lncRNA PTPRG-AS1/miR-124-3/LHX2 axis. The corresponding functions were verified in the complementation test. The levels of LHX2 and Notch pathway-related proteins were detected by Western blot. PTPRG-AS1 was upregulated in NPC cell lines and tissues. PTPRG-AS1 knockdown decreased NPC cell proliferation and promoted radiotherapy-induced apoptosis and cell radiosensitivity. PTPRG-AS1 upregulated LHX2 as a ceRNA of miR-124-3p. miR-124-3p inhibition partially reversed PTPRG-AS1 silencing-induced NPC cell radiosensitivity. miR-124-3p targeted LHX2. LHX2 overexpression attenuated the miR-124-3p overexpression-induced NPC cell radiosensitivity. LHX2 attenuated NPC cell radiosensitivity by activating the Notch pathway. Briefly, lncRNA PTPRG-AS1 reduced NPC cell radiosensitivity by regulating the miR-124-3p/LHX2 axis through the ceRNA mechanism.

Targeting the DNA Damage Response for Cancer Therapy by Inhibiting the Kinase Wee1

Cancer cells typically heavily rely on the G2/M checkpoint to survive endogenous and exogenous DNA damage, such as genotoxic stress due to genome instability or radiation and chemotherapy. The key regulator of the G2/M checkpoint, the cyclin-dependent kinase 1 (CDK1), is tightly controlled, including by its phosphorylation state. This posttranslational modification, which is determined by the opposing activities of the phosphatase cdc25 and the kinase Wee1, allows for a more rapid response to cellular stress than via the synthesis or degradation of modulatory interacting proteins, such as p21 or cyclin B. Reducing Wee1 activity results in ectopic activation of CDK1 activity and drives premature entry into mitosis with unrepaired or under-replicated DNA and causing mitotic catastrophe. Here, we review efforts to use small molecule inhibitors of Wee1 for therapeutic purposes, including strategies to combine Wee1 inhibition with genotoxic agents, such as radiation therapy or drugs inducing replication stress, or inhibitors of pathways that show synthetic lethality with Wee1. Furthermore, it become increasingly clear that Wee1 inhibition can also modulate therapeutic immune responses. We will discuss the mechanisms underlying combination treatments identifying both cell intrinsic and systemic anti-tumor activities.