Paclitaxel pretreatment overcomes hypoxia inducible factor-1α-induced radioresistance acquisition of human hepatoma and lung adenocarcinoma cells

Radioresistance in Hepatocellular Carcinoma: Biological Bases and Therapeutic Implications

Hepatocellular carcinoma (HCC) is a malignant tumor with high morbidity and mortality. Radiotherapy technology is a common treatment modality that can be used in all stages of HCC. However, in some cases, radiotherapy fails in clinical practice mainly because of the patient's resistance to radiotherapy, creating a bottleneck for future breakthroughs. HCC radiosensitivity is primarily related to DNA double-strand break repair, cellular autophagy, cell cycle, cellular metabolism, and hypoxic environmental regulators. Therefore, a comprehensive understanding of its molecular mechanisms will be of immense importance in reversing HCC radioresistance. In this review, we provide a comprehensive overview of the mechanism of action of radiotherapy on HCC, the cellular and molecular basis of radiation resistance in HCC, related treatment modalities, and future prospects.

P-Y/G@NHs sensitizes non-small cell lung cancer cells to radiotherapy via blockage of the PI3K/AKT signaling pathway

Radioresistance represents a common phenomenon found in cancer treatment. Herein, the current study sought to evaluate the effects of a nanodrug delivery system of YSAYPDSVPMMS (YSA) peptide-modified gold nanoparticles-dextran-based hydrogel loaded with paclitaxel-succinic anhydride (P-Y/G@NHs) on non-small cell lung cancer (NSCLC) cell radiosensitivity. Firstly, utilizing the coupling reaction and layer-by-layer assembly technique, P-Y/G@NHs was prepared. The therapeutic effects of the P-Y/G@NHs in NSCLC cells in relation to the PI3K/AKT signaling pathway were examined by assessing the colony formation, apoptosis, and reactive oxygen species (ROS) generation of A549 cells under 10 Gy X-rays irradiation. Moreover, A549 tumor-bearing mice were generated to further validate the therapeutic effect in vivo. We confirmed the successful conjugation of the nanocomposite. Under 10 Gy X-rays irradiation, P-Y/G@NHs reduced the number of colonies of A549 cells, while inducing both cell apoptosis and ROS production. Moreover, P-Y/G@NHs enhanced the radiosensitivity of A549 cells by inhibiting the PI3K/AKT signaling pathway. In vivo fluorescence experiments validated that P-Y/G@NHs effectively-targeted and accumulated at the tumor site in nude mice, thus augmenting the radiosensitivity of tumors without significant immune toxicity or side effects. Conclusively, our findings highlighted that P-Y/G@NHs significantly enhanced the radiosensitivity of NSCLC cells by repressing the PI3K/AKT signaling pathway.

Targeting Epithelial-to-Mesenchymal Transition in Radioresistance: Crosslinked Mechanisms and Strategies

Radiotherapy exerts a crucial role in curing cancer, however, its treatment efficiency is mostly limited due to the presence of radioresistance. Epithelial-to-mesenchymal transition (EMT) is a biological process that endows the cancer cells with invasive and metastatic properties, as well as radioresistance. Many potential mechanisms of EMT-related radioresistance being reported have broaden our cognition, and hint us the importance of an overall understanding of the relationship between EMT and radioresistance. This review focuses on the recent progresses involved in EMT-related mechanisms in regulating radioresistance, irradiation-mediated EMT program, and the intervention strategies to increase tumor radiosensitivity, in order to improve radiotherapy efficiency and clinical outcomes of cancer patients.

Hypoxia-Induced Cancer Cell Responses Driving Radioresistance of Hypoxic Tumors: Approaches to Targeting and Radiosensitizing

Simple Summary

Some regions of aggressive malignancies experience hypoxia due to inadequate blood supply. Cancer cells adapting to hypoxic conditions somehow become more resistant to radiation exposure and this decreases the efficacy of radiotherapy toward hypoxic tumors. The present review article helps clarify two intriguing points: why hypoxia-adapted cancer cells turn out radioresistant and how they can be rendered more radiosensitive. The critical molecular targets associated with intratumoral hypoxia and various approaches are here discussed which may be used for sensitizing hypoxic tumors to radiotherapy.

Abstract

Within aggressive malignancies, there usually are the “hypoxic zones”—poorly vascularized regions where tumor cells undergo oxygen deficiency through inadequate blood supply. Besides, hypoxia may arise in tumors as a result of antiangiogenic therapy or transarterial embolization. Adapting to hypoxia, tumor cells acquire a hypoxia-resistant phenotype with the characteristic alterations in signaling, gene expression and metabolism. Both the lack of oxygen by itself and the hypoxia-responsive phenotypic modulations render tumor cells more radioresistant, so that hypoxic tumors are a serious challenge for radiotherapy. An understanding of causes of the radioresistance of hypoxic tumors would help to develop novel ways for overcoming this challenge. Molecular targets for and various approaches to radiosensitizing hypoxic tumors are considered in the present review. It is here analyzed how the hypoxia-induced cellular responses involving hypoxia-inducible factor-1, heat shock transcription factor 1, heat shock proteins, glucose-regulated proteins, epigenetic regulators, autophagy, energy metabolism reprogramming, epithelial–mesenchymal transition and exosome generation contribute to the radioresistance of hypoxic tumors or may be inhibited for attenuating this radioresistance. The pretreatments with a multitarget inhibition of the cancer cell adaptation to hypoxia seem to be a promising approach to sensitizing hypoxic carcinomas, gliomas, lymphomas, sarcomas to radiotherapy and, also, liver tumors to radioembolization.

Role of metabolism in cancer cell radioresistance and radiosensitization methods

BACKGROUND

Radioresistance is a major factor leading to the failure of radiotherapy and poor prognosis in tumor patients. Following the application of radiotherapy, the activity of various metabolic pathways considerably changes, which may result in the development of resistance to radiation.

MAIN BODY

Here, we discussed the relationships between radioresistance and mitochondrial and glucose metabolic pathways, aiming to elucidate the interplay between the tumor cell metabolism and radiotherapy resistance. In this review, we additionally summarized the potential therapeutic targets in the metabolic pathways.

SHORT CONCLUSION

The aim of this review was to provide a theoretical basis and relevant references, which may lead to the improvement of the sensitivity of radiotherapy and prolong the survival of cancer patients.

γ-Glutamylcysteine synthetase (γ-GCS) as a target for overcoming chemo- and radio-resistance of human hepatocellular carcinoma cells

AIMS

This study uncovered that the genetically endowed intracellular glutathione contents (iGSH) regulated by the catalytic subunit of γ‑glutamylcysteine synthetase heavy chain (γ‑GCSh) as a prime target for overcoming both the inherited and stimuli-activated chemo- and radio-resistance of hepatocellular carcinoma (HCC) cells.

MAIN METHODS

Reactive oxygen species (ROS) production and mitochondrial membrane potential (Δψm) were determined by the probe-based flow cytometry. The TUNEL assay was used as an index of radio-sensitivity and the MTT assay was used as an index of chemo-sensitivity against various anti-cancer agents. iGSH and γ‑GCSh activity were measured by HPLC methods. γ‑GCSh-overexpressing GCS30 cell line was established by tetracycline-controlled Tet-OFF gene expression system in SK-Hep-1 cells.

KEY FINDINGS

The relative radio-sensitivities of a panel of five HCC cells were found to be correlated negatively with both the contents of iGSH and their corresponding γ‑GCSh activities with an order of abundance being Hep G2 > Hep 3B > J5 > Mahlavu > SK-Hep-1, respectively. Similarly, the cytotoxicity response patterns of these HCC cells against arsenic trioxide (ATO), a ROS-producing anti-cancer drug, were exactly identical to the order of ranking instigated by the radiotherapy (RT) treatment. Next, γ‑GCSh-overexpressing GCS30 cells were found to possess excellent ability to profoundly mitigate both the drop of Δψm and apoptotic TUNEL-positive cell population engendered by ATO, cisplatin, doxorubicin, and RT treatments.

SIGNIFICANCE

Our data unequivocally demonstrate that γ‑GCSh may represent a prime target for overcoming anti-cancer drugs and RT resistance for HCC cells.