Altered Mitochondrial Dynamics, Biogenesis, and Functions in the Paclitaxel-Resistant Lung Adenocarcinoma Cell Line A549/Taxol

Blocking lncRNA HCG18 re-sensitizes Taxol resistant lung cancer cells to Taxol through modulating the miR-34a-5p/HDAC1 axis

Lung cancer is one of the most frequently diagnosed cancers worldwide, associated with a poor survival rate. Taxol (Paclitaxel) is commonly used as a chemotherapeutic treatment for advanced lung cancers. While Taxol has improved clinical outcomes for lung cancer patients, a significant number of them develop resistance to Taxol, resulting in treatment failure. The role of the long noncoding RNA HCG18 in lung cancer and Taxol resistance has not yet been fully understood. To investigate this, we examined the expression of HCG18 and miR-34a-5p in lung tumors and normal lung tissues using qRT-PCR. We also assessed Taxol resistance through cell viability and apoptosis assays. Through the starBase online service, we analyzed the interactions between lncRNA and mRNA as well as miRNA and mRNA. We further validated the association between lncRNA and miRNA through luciferase and RNA pull-down assays. Our findings demonstrated that HCG18 was significantly upregulated in lung cancer tissues compared to normal lung tissues. Silencing HCG18 increased the sensitivity of lung cancer cells to Taxol. Additionally, our study established a Taxol-resistant cell line and observed a substantial upregulation of HCG18 in Taxol-resistant lung cancer cells. Bioinformatic analysis predicted that HCG18 could bind to miR-34a-5p, forming a competing endogenous RNA network, which was confirmed through luciferase assay. We found that miR-34a-5p was downregulated in lung cancer tissues and negatively correlated with Taxol resistance, as it directly bound to the 3'UTR region of HDAC1. Further results showed that inhibition of HCG18 significantly increased miR-34a-5p expression and sensitized lung cancer cells to Taxol. This sensitization could be reversed by inhibiting miR-34a-5p. Finally, we demonstrated in a xenograft mouse model that inhibition of HCG18 sensitized Taxol-resistant lung cancer cells to Taxol treatment by modulating the miR-34a-5p-HDAC1 axis. In conclusion, our in vitro and in vivo results uncover a novel molecular mechanism by which HCG18 promotes Taxol resistance through modulation of the miR-34a-5p/HDAC1 axis. These findings contribute to the diagnosis and treatment of chemo-resistant lung cancer.

Inhibition of Drp1 orchestrates the responsiveness of breast cancer cells to paclitaxel but insignificantly relieves paclitaxel-related ovarian damage in mice

Chemoresistance and chemotherapy-related ovarian damage are well-reported in breast cancer (BC) young patients. Herein, the inhibition of the mitochondrial fission was invested to explore its chemosensitizing role in Paclitaxel (PTX)-resistant cells, and its ability to restore the ovarian integrity in mice receiving PTX or cisplatin chemotherapy. To establish these aims, PTX-resistance was generated in BC cells, which were treated with PTX in combination with Drp1 deficiency, via mdivi-1, or Drp1-specific siRNA transfection. Furthermore, the alterations in the ovarian structure and the endocrine-related hormones were explored in mice receiving repetitive doses of PTX or cisplatin. We found that combining PTX with mdivi-1 improved cell responsiveness to PTX, induced apoptosis- and autophagy-mediated cell death, and relieved cellular oxidative stress. Additionally, the expression of PCNA1 and cyclin B1 genes were downregulated, meanwhile, p53, p21, and mitochondrial fusion proteins (Mfu1&Mfu2) were increased. The in vivo investigations in mice demonstrated that PTX induced gonadotoxic damage similar to cisplatin, whereas dual treatment of mice with PTX+ mdivi-1 failed to restore their normal follicular count and the circulating levels of E2 and AMH hormones. These results suggested that combining Drp1 inhibition with PTX resensitized breast cancer cells to PTX but failed to offer enough protection against chemotherapy-related gonadotoxicity.

Downregulation of angulin-1/LSR induces malignancy via upregulation of EGF-dependent claudin-2 and TGF-β-dependent cell metabolism in human lung adenocarcinoma A549 cells

Abnormal expression of bicellular tight junction claudins, including claudin-2 are observed during carcinogenesis in human lung adenocarcinoma. However, little is known about the role of tricellular tight junction molecule angulin-1/lipolysis-stimulated lipoprotein receptor (LSR). In the lung adenocarcinoma tissues examined in the present study, expression of claudin-2 was higher than in normal lung tissues, while angulin-1/LSR was poorly or faintly expressed. We investigated how loss of angulin-1/LSR affects the malignancy of lung adenocarcinoma cell line A549 and normal human lung epithelial (HLE) cells. The EGF receptor tyrosine kinase inhibitor AG1478 prevented the increase of claudin-2 expression induced by EGF in A549 cells. Knockdown of LSR induced expression of claudin-2 at the protein and mRNA levels and AG1478 prevented the upregulation of claudin-2 in A549 cells. Knockdown of LSR induced cell proliferation, cell migration and cell metabolism in A549 cells. Knockdown of claudin-2 inhibited the cell proliferation but did not affect the cell migration or cell metabolism of A549 cells. The TGF-β type I receptor inhibitor EW-7197 prevented the decrease of LSR and claudin-2 induced by TGF-β1 in A549 cells and 2D culture of normal HLE cells. EW-7197 prevented the increase of cell migration and cell metabolism induced by TGF-β1 in A549 cells. EW-7197 prevented the increase of epithelial permeability of FITC-4kD dextran induced by TGF-β1 in 2.5D culture of normal HLE cells. In conclusion, downregulation of angulin-1/LSR induces malignancy via EGF-dependent claudin-2 and TGF-β-dependent cell metabolism in human lung adenocarcinoma.

Mitochondria-Shaping Proteins and Chemotherapy

The emergence, in recent decades, of an entirely new area of “Mitochondrial dynamics”, which consists principally of fission and fusion, reflects the recognition that mitochondria play a significant role in human tumorigenesis and response to therapeutics. Proteins that determine mitochondrial dynamics are referred to as “shaping proteins”. Marked heterogeneity has been observed in the response of tumor cells to chemotherapy, which is associated with imbalances in mitochondrial dynamics and function leading to adaptive and acquired resistance to chemotherapeutic agents. Therefore, targeting mitochondria-shaping proteins may prove to be a promising approach to treat chemotherapy resistant cancers. In this review, we summarize the alterations of mitochondrial dynamics in chemotherapeutic processing and the antitumor mechanisms by which chemotherapy drugs synergize with mitochondria-shaping proteins. These might shed light on new biomarkers for better prediction of cancer chemosensitivity and contribute to the exploitation of potent therapeutic strategies for the clinical treatment of cancers.

Primary high-grade serous ovarian cancer cells are sensitive to senescence induced by carboplatin and paclitaxel in vitro

BACKGROUND

Various types of normal and cancer cells undergo senescence in response to carboplatin and paclitaxel, which are considered the gold standard treatments in ovarian cancer management. Surprisingly, the effect of these drugs on ovarian cancer cell senescence remained unknown.

METHODS

The experiments were conducted on primary high-grade serous ovarian cancer cells. Molecular markers of senescence were evaluated using cytochemistry and immunofluorescence. Cell cycle distribution was analyzed using flow cytometry. Expression of cyclins and signaling pathways was tested using western blot. Telomere length and telomerase activity were measured using qPCR, and the colocalization of telomeres with DNA damage foci using immuno-FISH. Oxidative stress-related parameters were quantified using appropriate fluorescence probes. Production of cancerogenic agents was analyzed using qPCR and ELISA.

RESULTS

Carboplatin applied with paclitaxel induces senescence of ovarian cancer cells in vitro. This activity was reflected by permanent G2/M growth arrest, a high fraction of cells expressing senescence biomarkers (SA-β-Gal and γ-H2A.X), upregulated expression of p16, p21, and p53 cell cycle inhibitors, and decreased expression of cyclin B1. Neither telomere length nor telomerase activity changed in the senescent cells, and the majority of DNA damage was localized outside telomeres. Moreover, drug-treated cancer cells exhibited increased production of STAT3 protein, overproduced superoxide and peroxides, and increased mitochondrial mass. They were also characterized by upregulated ANG1, CCL11, IL-6, PDGF-D, TIMP-3, TSP-1, and TGF-β1 at the mRNA and/or protein level.

CONCLUSIONS

Our findings imply that conventional chemotherapy may elicit senescence in ovarian cancer cells, which may translate to the development of a cancer-promoting phenotype, despite the inability of these cells to divide.

Mitochondrial dynamics regulators: implications for therapeutic intervention in cancer

Regardless of the recent advances in therapeutic developments, cancer is still among the primary causes of death globally, indicating the need for alternative therapeutic strategies. Mitochondria, a dynamic organelle, continuously undergo the fusion and fission processes to meet cell requirements. The balanced fission and fusion processes, referred to as mitochondrial dynamics, coordinate mitochondrial shape, size, number, energy metabolism, cell cycle, mitophagy, and apoptosis. An imbalance between these opposing events alters mitochondWangrial dynamics, affects the overall mitochondrial shape, and deregulates mitochondrial function. Emerging evidence indicates that alteration of mitochondrial dynamics contributes to various aspects of tumorigenesis and cancer progression. Therefore, targeting the mitochondrial dynamics regulator could be a potential therapeutic approach for cancer treatment. This review will address the role of imbalanced mitochondrial dynamics in mitochondrial dysfunction during cancer progression. We will outline the clinical significance of mitochondrial dynamics regulators in various cancer types with recent updates in cancer stemness and chemoresistance and its therapeutic potential and clinical utility as a predictive biomarker.

Therapeutic potential of targeting mitochondrial dynamics in cancer

In the past mitochondria were considered as the "powerhouse" of cell, since they generate more than 90% of ATP in aerobic conditions through the oxidative phosphorylation. However, based on the current knowledge, mitochondria play several other cellular functions, including participation in calcium homeostasis, generation of free radicals and oxidative species, triggering/regulation of apoptosis, among others. Additionally, previous discoveries recognized mitochondria as highly dynamic structures, which undergo morphological alterations resulting in long or short fragments inside the living cells. This highly regulated process was referred as mitochondrial dynamics and involves mitochondrial fusion and fission. Thus, the number of mitochondria and the morphology of mitochondrial networks depend on the mitochondrial dynamics, biogenesis, and mitophagy. In each cell, there is a delicate balance between fusion and fission to allow the maintenance of appropriate mitochondrial functions. It has been proposed that the fusion and fission dynamics process controls cell cycle, metabolism, and survival, being implicated in a wide range of physiological and pathological conditions. Mitochondrial fusion is mediated by dynamin-like proteins, including mitofusin 1 (MFN1), mitofusin 2 (MFN2), and optic atrophy 1 protein (OPA1). Conversely, mitochondrial fission results in a large number of small fragments, which is mediated mainly by dynamin-related protein 1 (DRP1). Interestingly, there is growing evidence proposing that tumor cells modify the mitochondrial dynamics rheostat in order to gain proliferative and survival advantages. Increased mitochondrial fission has been reported in several types of human cancer cells (melanoma, ovarian, breast, lung, thyroid, glioblastoma, and others) and some studies have reported a possible direct correlation between increased mitochondrial fusion and chemoresistance of tumor cells. Here, the current knowledge about alterations of mitochondrial dynamics in cancer will be reviewed and its potential as a target for adjuvant cancer chemotherapy will be discussed.