mTORC1 inhibitor RAD001 (everolimus) enhances non-small cell lung cancer cell radiosensitivity in vitro via suppressing epithelial-mesenchymal transition

E-cadherin re-expression: Its potential in combating TRAIL resistance and reversing epithelial-to-mesenchymal transition

The major limitation of conventional chemotherapy drugs is their lack of specificity for cancer cells. As a selective apoptosis-inducing agent, tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has emerged as an attractive alternative. However, most of the cancer cells are found to be either intrinsically resistant to the TRAIL protein or may develop resistance after multiple treatments, and TRAIL resistance can induce epithelial-to-mesenchymal transition (EMT) at a later stage, promoting cancer invasion and migration. Interestingly, E-cadherin loss has been linked to TRAIL resistance and initiation of EMT, making E-cadherin re-expression a potential target to overcome these obstacles. Recent research suggests that re-expressing E-cadherin may reduce TRAIL resistance by enhancing TRAIL-induced apoptosis and preventing EMT by modulating EMT signalling factors. This reversal of EMT, can also aid in improving TRAIL-induced apoptosis. Therefore, this review provides remarkable insights into the mechanisms underlying E-cadherin re-expression, clinical implications, and potentiation, as well as the research gaps of E-cadherin re-expression in the current cancer treatment.

The rapid proximity labeling system PhastID identifies ATP6AP1 as an unconventional GEF for Rheb

Rheb is a small G protein that functions as the direct activator of the mechanistic target of rapamycin complex 1 (mTORC1) to coordinate signaling cascades in response to nutrients and growth factors. Despite extensive studies, the guanine nucleotide exchange factor (GEF) that directly activates Rheb remains unclear, at least in part due to the dynamic and transient nature of protein-protein interactions (PPIs) that are the hallmarks of signal transduction. Here, we report the development of a rapid and robust proximity labeling system named Pyrococcus horikoshii biotin protein ligase (PhBPL)-assisted biotin identification (PhastID) and detail the insulin-stimulated changes in Rheb-proximity protein networks that were identified using PhastID. In particular, we found that the lysosomal V-ATPase subunit ATP6AP1 could dynamically interact with Rheb. ATP6AP1 could directly bind to Rheb through its last 12 amino acids and utilizes a tri-aspartate motif in its highly conserved C-tail to enhance Rheb GTP loading. In fact, targeting the ATP6AP1 C-tail could block Rheb activation and inhibit cancer cell proliferation and migration. Our findings highlight the versatility of PhastID in mapping transient PPIs in live cells, reveal ATP6AP1's role as an unconventional GEF for Rheb, and underscore the importance of ATP6AP1 in integrating mTORC1 activation signals through Rheb, filling in the missing link in Rheb/mTORC1 activation.

Long non-coding RNA CCAT1 acts as an oncogene to promote radiation resistance in lung adenocarcinoma: an epigenomics-based investigation

Long non-coding RNAs (lncRNAs) appear to be the crucial modulators in various processes and critically influence the oncogenesis. As one of the LncRNAs, LncRNA CCAT1 has been reported to be closely associated with the progression multiple cancers, but its role in modulating the radioresistance of lung adenocarcinoma (LUAD) remains unclear. In our present study, we screened the potential radioresistance related LncRNAs in LUAD based on the data from The Cancer Genome Atlas (TCGA) database. Data suggested that CCAT1 was abundantly expressed in LUAD and CCAT1 was significantly associated with poor prognosis and radioresistance. Moreover, our in vitro experiments showed that radiation treatment could trigger elevated expression of CCAT1 in the human LUAD cell lines. Further loss/gain-of-function investigations indicated that CCAT1 knockdown significantly inhibited cell proliferation, migration and promoted cell apoptosis in NCI-H1299 cells under irradiation, whereas CCAT1 overexpression in A549 cells yield the opposite effects. In summary, we identified the promoting role of CCAT1 in radioresistance of LUAD, which may provide a theoretical basis for radiotherapy sensitization of LUAD.

MRPL51 is a downstream target of FOXM1 in promoting the malignant behaviors of lung adenocarcinoma

Mitochondrial ribosome protein L51 (MRPL51) is a 39S subunit protein of the mitochondrial ribosome. Its dysregulation may be involved in non-small cell lung cancer. The present study aimed to explore MRPL51 expression in lung adenocarcinoma (LUAD) and normal lung tissues, as well as its regulatory effects on malignant LUAD behaviors. In addition, the role of forkhead box protein M1 (FOXM1) in MRPL51 transcription was studied. Bioinformatics analysis and subsequent in vitro experiments, including western blotting, immunofluorescent staining, Transwell invasion assay, dual-luciferase assay and chromatin immunoprecipitation quantitative PCR were conducted. The results demonstrated that MRPL51 expression was upregulated at both the mRNA and protein levels in LUAD tissues compared with normal lung tissues. Gene Set Enrichment Analysis demonstrated that LUAD tissues with higher MRPL51 expression also had higher expression levels of genes enriched in multiple gene sets, including 'DNA_REPAIR', 'UNFOLDED_PROTEIN_RESPONSE', 'MYC_TARGETS_V1', 'OXIDATIVE_ PHOSPHORYLATION', 'MTORC1_SIGNALING', 'REACTIVE_OXYGEN_SPECIES_PATHWAY', 'MYC_ TARGETS_V2', 'E2F_TARGETS' and 'G2M_ CHECKPOINT'. MRPL51 expression was positively correlated with 'cell cycle', 'DNA damage', 'DNA repair', epithelial-mesenchymal transition ('EMT'), 'invasion' and 'proliferation' of LUAD cells at the single-cell level. Compared to the negative control, MRPL51 knockdown decreased N-cadherin and vimentin expression but increased E-cadherin expression in A549 and Calu-3 cells. MRPL51 knockdown suppressed cell proliferation, induced G1 phase arrest and decreased cell invasion. Patients with LUAD and higher MRPL51 expression had a significantly shorter overall survival (OS). FOXM1 could bind to the MRPL51 gene promoter and activate its transcription. In conclusion, MRPL51 was transcriptionally activated by FOXM1 in LUAD and contributed to the malignant behaviors of tumor cells, including EMT, cell cycle progression and invasion. High MRPL51 expression may be a prognostic biomarker indicating poor OS.

Unraveling the Post-Translational Modifications and therapeutical approach in NSCLC pathogenesis

Non-Small Cell Lung Cancer (NSCLC) is the most prevalent kind of lung cancer with around 85% of total lung cancer cases. Despite vast therapies being available, the survival rate is low (5 year survival rate is 15%) making it essential to comprehend the mechanism for NSCLC cell survival and progression. The plethora of evidences suggests that the Post Translational Modification (PTM) such as phosphorylation, methylation, acetylation, glycosylation, ubiquitination and SUMOylation are involved in various types of cancer progression and metastasis including NSCLC. Indeed, an in-depth understanding of PTM associated with NSCLC biology will provide novel therapeutic targets and insight into the current sophisticated therapeutic paradigm. Herein, we reviewed the key PTMs, epigenetic modulation, PTMs crosstalk along with proteogenomics to analyze PTMs in NSCLC and also, highlighted how epi‑miRNA, miRNA and PTM inhibitors are key modulators and serve as promising therapeutics.

Current Landscape of Therapeutic Resistance in Lung Cancer and Promising Strategies to Overcome Resistance

Simple Summary

Despite an initial response to therapy, many lung cancer patients inevitably develop resistance to therapy leading to decreased duration of response and success of treatment. Recent research aims to elucidate mechanisms of resistance in order to improve drug response and treatment outcomes. By utilizing multidisciplinary approaches that target various resistance mechanism, it may be possible to delay development of treatment resistance or even resensitize cancers. This review aims to discuss novel approaches to improve clinical outcomes, delay the occurrence of resistance, and overcome resistance.

Abstract

Lung cancer is one of the leading causes of cancer-related deaths worldwide with a 5-year survival rate of less than 18%. Current treatment modalities include surgery, chemotherapy, radiation therapy, targeted therapy, and immunotherapy. Despite advances in therapeutic options, resistance to therapy remains a major obstacle to the effectiveness of long-term treatment, eventually leading to therapeutic insensitivity, poor progression-free survival, and disease relapse. Resistance mechanisms stem from genetic mutations and/or epigenetic changes, unregulated drug efflux, tumor hypoxia, alterations in the tumor microenvironment, and several other cellular and molecular alterations. A better understanding of these mechanisms is crucial for targeting factors involved in therapeutic resistance, establishing novel antitumor targets, and developing therapeutic strategies to resensitize cancer cells towards treatment. In this review, we summarize diverse mechanisms driving resistance to chemotherapy, radiotherapy, targeted therapy, and immunotherapy, and promising strategies to help overcome this therapeutic resistance.

Caffeic acid phenethyl ester induces radiosensitization via inhibition of DNA damage repair in androgen-independent prostate cancer cells

In the present study, we evaluated the radiomodulatory potential of caffeic acid phenethyl ester (CAPE), an active component of traditional herbal medicine propolis. CAPE has been identified as a potent anticancer agent in multiple cancer types and is reported to have the dual role of radioprotection and radiosensitization. However, the radiomodulatory potential of CAPE in prostate cancer (PCa), which eventually becomes radioresistant is not known. Therefore, we studied the effect of co-treatment of CAPE and gamma radiation on androgen-independent DU145 and PC3 cells. The combination treatment sensitized PCa cells to radiation in a dose-dependent manner. The radiosensitizing effect of CAPE was observed in both cell lines. CAPE enhanced the level of ionizing radiation (IR)-induced gamma H2AX foci and cell death by apoptosis. The combination treatment also decreased the migration potential of PCa cells. This was confirmed by increased expression of E-cadherin and decrease in vimentin expression. CAPE sensitized PCa cells to radiation in vitro and induced apoptosis, augmented phosphorylation of Akt/mTOR, and hampered cell migration. At the mechanistic level, co-treatment of CAPE and IR inhibited cell growth by decreasing RAD50 and RAD51 proteins involved in DNA repair. This resulted in enhanced DNA damage and cell death. CAPE might represent a promising new adjuvant for the treatment of hormone-refractory radioresistant PCa.

Clinical and Preclinical Outcomes of Combining Targeted Therapy With Radiotherapy

In the era of precision medicine, radiation medicine is currently focused on the precise delivery of highly conformal radiation treatments. However, the tremendous developments in targeted therapy are yet to fulfill their full promise and arguably have the potential to dramatically enhance the radiation therapeutic ratio. The increased ability to molecularly profile tumors both at diagnosis and at relapse and the co-incident progress in the field of radiogenomics could potentially pave the way for a more personalized approach to radiation treatment in contrast to the current ‘‘one size fits all’’ paradigm. Few clinical trials to date have shown an improved clinical outcome when combining targeted agents with radiation therapy, however, most have failed to show benefit, which is arguably due to limited preclinical data. Several key molecular pathways could theoretically enhance therapeutic effect of radiation when rationally targeted either by directly enhancing tumor cell kill or indirectly through the abscopal effect of radiation when combined with novel immunotherapies. The timing of combining molecular targeted therapy with radiation is also important to determine and could greatly affect the outcome depending on which pathway is being inhibited.

Vascular normalization in immunotherapy: A promising mechanisms combined with radiotherapy

Leakage and compression of blood vessels may result in deprivation of blood flow to a large number of tumor tissues, which can lead to tumor hypoxia. Hypoxia induces an increase in the expression of hypoxia-inducible factor 1 in tumor cells, which induces angiogenesis in tumors through the high expression of vascular endothelial growth factor, thereby forming a positive feedback vicious circle. Improving hypoxia by normalizing blood vessels and improving radiosensitivity by immunotherapy has emerged as a new application of combined immunotherapy and radiotherapy. Interferon γ produced by CD4 + /CD8 + T cells, induced by immune checkpoint inhibitors, plays an important role in the normalization of blood vessels; tumor-associated eosinophils also play a role in the process of immunotherapy-induced blood vessel normalization. In addition, the reduction in regulatory T cells induced by immune checkpoint inhibitors can increase eosinophil levels, which promotes the further development of vascular normalization mechanisms. This review focuses on the mechanism of immunotherapy to normalize blood vessels, and proposes a good prospect for improving hypoxia. Due to the narrow vascular normalization window of anti-angiogenesis therapy, discovery of the vascular normalization effect of immunotherapy provides a new idea for the combined application of immunotherapy and radiotherapy. The enlarged vascular normalization window and improved hypoxia provide a good opportunity for the subsequent implementation of radiotherapy. The above sorting and analysis may pave the way for a promising strategy for cancer treatment via combined immunotherapy and radiotherapy.

miR-4634 augments the anti-tumor effects of RAD001 and associates well with clinical prognosis of non-small cell lung cancer

MicroRNA (miRNA) is involved in the physiological and pathological processes of various malignancies. In this study, miRNA microarray analysis showed that miR-4634 levels in A549 cells increased significantly after everolimus (RAD001) treatment. Decreased expression of miR-4634 was also found in non-small-cell lung carcinoma (NSCLC) cell lines and patients’ tumors by qPCR. Additionally, a combination of miR-4634 and RAD001 exerted synergistic antitumor efficacy by inhibiting cell proliferation, migration, and colony formation. High expression of miR-4634 was significantly more common in non-cancerous lung tissue than adenocarcinoma or squamous cell carcinoma tissue (72.8%, 45.7%, and 50.9%, respectively; P < 0.001). Furthermore, high expression of miR-4634 was found to be more frequent in patients without lymph node metastasis (P = 0.037) by in-situ hybridization. Importantly, through univariate and multivariate analysis, high miR-4634 expression was associated with better prognosis of NSCLC patients. In conclusion, miR-4634 may act as a tumor suppressor in NSCLC, and to augment the efficacy of RAD001, co-treatment of miR-4634 and RAD001 might be a potential mTOR-targeted cancer therapy strategy for NSCLC patients. High expression of miR-4634 could be an independent good prognostic biomarker for NSCLC.

Inhibition of autophagy improves resistance and enhances sensitivity of gastric cancer cells to cisplatin

Autophagy plays critical roles in tumorigenesis, while the effects of autophagy on chemoresistance of cancer cells had great disparity. This study aims to explore the impacts of autophagy on the sensitivity and resistance of gastric cancer cells to cisplatin (DDP). We firstly demonstrated that there was stronger autophagy activity in gastric cancer SGC-7901 cells than that in DDP-resisting SGC-7901/DDP cells. Then, we discovered that inhibiting autophagy by chloroquine (CQ) significantly enhanced the proliferation-inhibiting and apoptosis-inducing effects of DDP to SGC-7901 and SGC-7901/DDP cells. Moreover, CQ could partially reverse the resistance of SGC-7901/DDP cells to DDP in a concentration-dependent manner. However, the autophagy inducer everolimus (RAD001) had no obvious effects on the sensitivity of gastric cells to DDP. Mechanistically, we demonstrated that CQ might enhance the sensitivity of SGC-7901cells and improve the resistance of SGC-7901/DDP cells to DDP through inhibiting the mTORC1 pathway, especially to SGC-7901/DDP cells. Additionally, we found interfering Beclin-1 using Beclin-1 shRNA also enhanced the proliferation-inhibiting and apoptosis-inducing effects of DDP on gastric cancer cells by inhibiting phosphorylation of Akt. Our study shows that inhibiting autophagy could improve the chemoresistance and enhanced sensitivity of gastric cancer cells to DDP and provide a rationale for the administration of cisplatin combined with CQ for treating patients with gastric cancer.

mTOR-Mediated Antioxidant Activation in Solid Tumor Radioresistance

Radiotherapy is widely used for the treatment of cancer patients, but tumor radioresistance presents serious therapy challenges. Tumor radioresistance is closely related to high levels of mTOR signaling in tumor tissues. Therefore, targeting the mTOR pathway might be a strategy to promote solid tumor sensitivity to ionizing radiation. Radioresistance is associated with enhanced antioxidant mechanisms in cancer cells. Therefore, examination of the relationship between mTOR signaling and antioxidant mechanism-linked radioresistance is required for effective radiotherapy. In particular, the effect of mTOR signaling on antioxidant glutathione induction by the Keap1-NRF2-xCT pathway is described in this review. This review is expected to assist in the identification of therapeutic adjuvants to increase the efficacy of radiotherapy.