Autophagy in cellular transformation, survival and communication with the tumor microenvironment

Bidirectional regulation of the cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon gene pathway and its impact on hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) ranks as the fourth leading cause of cancer-related deaths in China, and the treatment options are limited. The cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) activates the stimulator of interferon gene (STING) signaling pathway as a crucial immune response pathway in the cytoplasm, which detects cytoplasmic DNA to regulate innate and adaptive immune responses. As a potential therapeutic target, cGAS-STING pathway markedly inhibits tumor cell proliferation and metastasis, with its activation being particularly relevant in HCC. However, prolonged pathway activation may lead to an immunosuppressive tumor microenvironment, which fostering the invasion or metastasis of liver tumor cells.

AIM

To investigate the dual-regulation mechanism of cGAS-STING in HCC.

METHODS

This review was conducted according to the PRISMA guidelines. The study conducted a comprehensive search for articles related to HCC on PubMed and Web of Science databases. Through rigorous screening and meticulous analysis of the retrieved literature, the research aimed to summarize and elucidate the impact of the cGAS-STING pathway on HCC tumors.

RESULTS

All authors collaboratively selected studies for inclusion, extracted data, and the initial search of online databases yielded 1445 studies. After removing duplicates, the remaining 964 records were screened. Ultimately, 55 articles met the inclusion criteria and were included in this review.

CONCLUSION

Acute inflammation can have a few inhibitory effects on cancer, while chronic inflammation generally promotes its progression. Extended cGAS-STING pathway activation will result in a suppressive tumor microenvironment.

PEG-modified carbon-based nanoparticles as tumor-targeted drug delivery system reducing doxorubicin-induced cardiotoxicity

Herein, a doxorubicin-loaded carbon-based drug delivery system, denoted as PC-DOX, composed of pH-responsive imine bond was developed for the tumor-targeted treatment. PC-DOX with a uniform particle size around 180 nm was synthesized by coating of as-synthesized hollow carbon-based nanoparticles (NPs) with dialdehyde PEG, which was used as carrier to attach DOX covalently through dynamic covalent bond. The unique structure endowed the advantages of specific tumor targeting and tumor microenvironment (TME) specific drug delivery capacity with PC-DOX. For the one hand, the tumor targeting caused by the enhanced permeability and retention (EPR) effect could significantly improve the tumor cellular uptake. For the other hand, the pH-responsiveness could realize the effective DOX accumulation in tumor tissues, avoiding the unwanted side effect to the normal tissues. As a result, PC-DOX with high DOX loading capacity (70.12%) and excellent biocompatibility, concurrently, presented a significant anti-tumor effect at a low mass concentration (DOX equivalent dose: 20 μg/mL). Another attractive characteristic of PC-DOX was the remarkable protective effect towards DOX-induced cardiotoxicity, which could be clearly observed from in vitro cellular, and animal assays. Compared with free DOX, the cardiomyocyte viability increased by average 30.58%, and the heart function was also significantly improved. This novel drug delivery nanoplatform provides a new method for the future clinical application of DOX in the cancer's therapeutics.

Overexpression of microRNA-96-5p inhibits autophagy and apoptosis and enhances the proliferation, migration and invasiveness of human breast cancer cells

MicroRNAs (miRNA/miR) are short non-coding RNAs that function in the endogenous regulation of genes. miRNAs serve important roles in cellular events such as apoptosis, cell proliferation, migration, invasion, autophagy and the cell cycle. They also control the genesis and progression of tumors. Autophagy is a self-digestive process that occurs as a response to stress, and serves two opposite roles in tumor promotion or inhibition that may result in resistance to therapy. A number of studies have revealed that miRNAs control autophagic activity by targeting autophagy-associated genes, particularly in cancer. These previous studies demonstrated that miR-96-5p is upregulated in several types of malignant tumors. However, other functions of miR-96-5p in breast cancer, particularly those that are associated with autophagy, remain unknown. miR-96-5p expression was demonstrated to be upregulated in breast cancer cells compared with in normal breast epithelial cells. The overexpression of miR-96-5p inhibited autophagy, particularly starvation-induced autophagy, in MCF-7 and MDA-MB-231 cells. In addition, this inhibitory effect may have resulted in the suppression of Forkhead box O1. Additionally, the overexpression of miR-96-5p may promote cell proliferation, migration and invasion and inhibit apoptosis in MCF-7 and MDA-MB-231 cells. These data indicate that miR-96-5p is involved in the progression of breast cancer cells and may represent a potential therapeutic target for the treatment of breast cancer.

Synergistic anti-tumour effects of tetrandrine and chloroquine combination therapy in human cancer: a potential antagonistic role for p21

BACKGROUND AND PURPOSE

Tetrandrine, a bisbenzylisoquinoline alkaloid isolated from the Chinese medicinal herb Stephaniae tetrandrae, has a long history in Chinese clinical applications to treat diverse diseases. Tetrandrine induced apoptosis or, at low concentrations, autophagy of human hepatocellular carcinoma cells. Here we have tested the effects of inhibitors of autophagy such as chloroquine, on the response to low concentrations of tetrandrine in cancer cells.

EXPERIMENTAL APPROACH

Cultures of several cancer cell lines, including Huh7, U251, HCT116 and A549 cells, were exposed to tetrandrine, chloroquine or a combination of these compounds. Cell viability and content of reactive oxygen species (ROS) were measured and synergy assessed by calculation of the combination index. Western blot and RT-PCR assays were also used along with fluorescence microscopy and histochemical techniques.

KEY RESULTS

Combinations of tetrandrine and chloroquine were more cytotoxic than the same concentrations used separately and these effects showed synergy. Such effects involved increased ROS generation and were dependent on caspase-3 but independent of Akt activity. Blockade of tetrandrine-induced autophagy with 3-methyladenine or bafilomycin-A1 induced apoptosis in cancer cells. Lack of p21 protein (p21(-/-) HCT116 cells) increased sensitivity to the apoptotic effects of the combination of tetrandrine and chloroquine. In a tumour xenograft model in mice, combined treatment with tetrandrine and chloroquine induced ROS accumulation and cell apoptosis, and decreased tumour growth.

CONCLUSIONS AND IMPLICATIONS

The combinations of tetrandrine and chloroquine exhibited synergistic anti-tumour activity, in vitro and in vivo. Our results suggest a novel therapeutic strategy for tumour treatment.