A drug combination targeting hypoxia induced chemoresistance and stemness in glioma cells

Genetic polymorphisms as potential pharmacogenetic biomarkers for platinum-based chemotherapy in non-small cell lung cancer

Platinum-based chemotherapy (PBC) is a widely used treatment for various solid tumors, including non-small cell lung cancer (NSCLC). However, its efficacy is often compromised by the emergence of drug resistance in patients. There is growing evidence that genetic variations may influence the susceptibility of NSCLC patients to develop resistance to PBC. Here, we provide a comprehensive overview of the mechanisms underlying platinum drug resistance and highlight the important role that genetic polymorphisms play in this process. This paper discussed the genetic variants that regulate DNA repair, cellular movement, drug transport, metabolic processing, and immune response, with a focus on their effects on response to PBC. The potential applications of these genetic polymorphisms as predictive indicators in clinical practice are explored, as are the challenges associated with their implementation.

Anti-Glioma Effects of Ligustilide or n-Butylphthalide on Their Own and the Synergistic Effects with Temozolomide via PI3K/Akt Signaling Pathway

Background

Ligustilide (LIG) and n-butylphthalide (NBP) have neuroprotective effects in cerebral ischemia; however, their roles in gliomas are not well-known.This study aimed to explore the anti-glioma effects of LIG and NBP individually and the synergistic effects of temozolomide (TMZ) via the PI3K/Akt Signaling Pathway.

Materials and Methods

Cytotoxicity of LIG and NBP alone and in combination with TMZ in U251 cells was determined using the CCk-8. The effect of compounds alone or in combination on cell migration was detected using the wound healing assay, and the invasion was evaluated by transwell assays, respectively. Cell apoptosis was quantified by flow cytometry and the changed expressions of proteins were detected by Western blotting.

Results

The results showed that LIG and NBP significantly inhibited the growth of U251 cells at concentrations of 4-10 µg/mL and 1.5-6 µg/mL in a dose-dependent manner (p<0.05, p<0.01). The combination of 20 µg/mL TMZ with LIG in the concentration range of 4-10 µg/mL or with NBP of 0.5-6 µg/mlachieved synergistic effect towardsU251 cells. LIG and NBP, alone or in combination with TMZ, markedly inhibited cell invasion (p< 0.001) and enhanced apoptosis (p< 0.05). The combination of TMZ with LIG or NBP markedly inhibited cell migration (p< 0.001). Western blot analysis showed that LIG, NBP, and TMZ, alone and in combination, significantly decreased the expression of Bcl-2, p-PI3K, and p-Akt, and increased the expression of Bax.

Conclusion

Both LIG and NBP exert anti-glioma effects on their own through the PI3K/Akt pathway and enhance TMZ-mediated anti-glioma efficiency via the same pathway.

The Role of Hypoxia and Cancer Stem Cells in Development of Glioblastoma

Glioblastoma multiform (GBM) is recognized as the most malignant brain tumor with a high level of hypoxia, containing a small population of glioblastoma stem like cells (GSCs). These GSCs have the capacity of self-renewal, proliferation, invasion and recapitulating the parent tumor, and are major causes of radio-and chemoresistance of GBM. Upregulated expression of hypoxia inducible factors (HIFs) in hypoxia fundamentally contributes to maintenance and progression of GSCs. Therefore, we thoroughly reviewed the currently acknowledged roles of hypoxia-associated GSCs in development of GBM. In detail, we recapitulated general features of GBM, especially GSC-related features, and delineated essential responses resulted from interactions between GSC and hypoxia, including hypoxia-induced signatures, genes and pathways, and hypoxia-regulated metabolic alterations. Five hypothesized GSC niches are discussed and integrated into one comprehensive concept: hypoxic peri-arteriolar niche of GSCs. Autophagy, another protective mechanism against chemotherapy, is also closely related to hypoxia and is a potential therapeutic target for GBM. In addition, potential causes of therapeutic resistance (chemo-, radio-, surgical-, immuno-), and chemotherapeutic agents which can improve the therapeutic effects of chemo-, radio-, or immunotherapy are introduced and discussed. At last, as a potential approach to reverse the hypoxic microenvironment in GBM, hyperbaric oxygen therapy (HBOT) might be an adjuvant therapy to chemo-and radiotherapy after surgery. In conclusion, we focus on demonstrating the important role of hypoxia on development of GBM, especially by affecting the function of GSCs. Important advantages have been made to understand the complicated responses induced by hypoxia in GBM. Further exploration of targeting hypoxia and GSCs can help to develop novel therapeutic strategies to improve the survival of GBM patients.

Synthesis and Significance of Arachidonic Acid, a Substrate for Cyclooxygenases, Lipoxygenases, and Cytochrome P450 Pathways in the Tumorigenesis of Glioblastoma Multiforme, Including a Pan-Cancer Comparative Analysis

Glioblastoma multiforme (GBM) is one of the most aggressive gliomas. New and more effective therapeutic approaches are being sought based on studies of the various mechanisms of GBM tumorigenesis, including the synthesis and metabolism of arachidonic acid (ARA), an omega-6 polyunsaturated fatty acid (PUFA). PubMed, GEPIA, and the transcriptomics analysis carried out by Seifert et al. were used in writing this paper. In this paper, we discuss in detail the biosynthesis of this acid in GBM tumors, with a special focus on certain enzymes: fatty acid desaturase (FADS)1, FADS2, and elongation of long-chain fatty acids family member 5 (ELOVL5). We also discuss ARA metabolism, particularly its release from cell membrane phospholipids by phospholipase A₂ (cPLA₂, iPLA₂, and sPLA₂) and its processing by cyclooxygenases (COX-1 and COX-2), lipoxygenases (5-LOX, 12-LOX, 15-LOX-1, and 15-LOX-2), and cytochrome P450. Next, we discuss the significance of lipid mediators synthesized from ARA in GBM cancer processes, including prostaglandins (PGE₂, PGD₂, and 15-deoxy-Δ^12,14-PGJ₂ (15d-PGJ₂)), thromboxane A₂ (TxA₂), oxo-eicosatetraenoic acids, leukotrienes (LTB₄, LTC₄, LTD₄, and LTE₄), lipoxins, and many others. These lipid mediators can increase the proliferation of GBM cancer cells, cause angiogenesis, inhibit the anti-tumor response of the immune system, and be responsible for resistance to treatment.

Antineoplastic multi-drug chemotherapy to sensitize tumors triggers multi-drug resistance and inhibits efficiency of maintenance treatment inglioblastoma cells

Combinations of the well-known antineoplastic agents 5-fluorouracil (5-Fu), cisplatin, and paclitaxel are employed to increase radiotherapy/immunotherapy efficacy against persistent and resistant tumors. However, data remains needed on the hormetic, chronic, and long-term side effects of these aggressive combination chemotherapies. Here we investigated cellular and molecular responses associated with these combined agents, and their potential to induce multi-drug resistance against the temozolomide (TMZ) and etoposide (EP) used in glioblastoma maintenance treatment. We analyzed resistance and survival signals in U87 MG cells using molecular probes, fluorescent staining, qRT-PCR, and immunoblot. Repeated treatment with combined 5-Fu, cisplatin, and paclitaxel induced cross-resistance against TMZ and EP. Resistant cells exhibited elevated gene/protein expression of MRP1/ABCC1, ABCC2, BRCP/ABCG2, and GST. Moreover, they managed oxidative stress, cell cycle, apoptosis, and autophagy signaling to ensure survival. In these groups TMZ and etoposide efficiency dramatically reduced. Our result suggests that combined high-dose treatments of classical antineoplastic agents to sensitize tumors may trigger multi-drug resistance and inhibit maintenance treatment. When deciding on antineoplastic combination therapy for persistent/resistant glioblastoma, we recommend analyzing the long-term hormetic and chronic effects on cross-resistance and multi-drug resistance in primary cell cultures from patients. See also the Graphical Abstract(Fig. 1).

Cellular landscaping of cisplatin resistance in cervical cancer

Cervical cancer (CC) caused by human papillomavirus (HPV) is one of the largest causes of malignancies in women worldwide. Cisplatin is one of the widely used drugs for the treatment of CC is rendered ineffective owing to drug resistance. This review highlights the cause of resistance and the mechanism of cisplatin resistance cells in CC to develop therapeutic ventures and strategies that could be utilized to overcome the aforementioned issue. These strategies would include the application of nanocarries, miRNA, CRIPSR/Cas system, and chemotherapeutics in synergy with cisplatin to not only overcome the issues of drug resistance but also enhance its anti-cancer efficiency. Moreover, we have also discussed the signaling network of cisplatin resistance cells in CC that would provide insights to develop therapeutic target sites and inhibitors. Furthermore, we have discussed the role of CC metabolism on cisplatin resistance cells and the physical and biological factors affecting the tumor microenvironments.

Up-Regulation of Cyclooxygenase-2 (COX-2) Expression by Temozolomide (TMZ) in Human Glioblastoma (GBM) Cell Lines

TMZ-resistance remains a main limitation in glioblastoma (GBM) treatment. TMZ is an alkylating agent whose cytotoxicity is modulated by O6-methylguanine-DNA methyltransferase (MGMT), whose expression is determined by MGMT gene promoter methylation status. The inflammatory marker COX-2 has been implicated in GBM tumorigenesis, progression, and stemness. COX-2 inhibitors are considered a GBM add-on treatment due to their ability to increase TMZ-sensitivity. We investigated the effect of TMZ on COX-2 expression in GBM cell lines showing different COX-2 levels and TMZ sensitivity (T98G and U251MG). β-catenin, MGMT, and SOX-2 expression was analyzed. The effects of NS398, COX-2 inhibitor, alone or TMZ-combined, were studied evaluating cell proliferation by the IncuCyte^® system, cell cycle/apoptosis, and clonogenic potential. COX-2, β-catenin, MGMT, and SOX-2 expression was evaluated by RT-PCR, Western blotting, and immunofluorescence and PGE2 by ELISA. Our findings, sustaining the role of COX-2/PGE2 system in TMZ-resistance of GBM, show, for the first time, a relevant, dose-dependent up-regulation of COX-2 expression and activity in TMZ-treated T98G that, in turn, correlated with chemoresistance. Similarly, all the COX-2-dependent signaling pathways involved in TMZ-resistance also resulted in being up-modulated after treatment with TMZ. NS398+TMZ was able to reduce cell proliferation and induce cell cycle arrest and apoptosis. Moreover, NS398+TMZ counteracted the resistance in T98G preventing the TMZ-induced COX-2, β-catenin, MGMT, and SOX-2 up-regulation.

Cyclooxygenase inhibition attenuates brain angiogenesis and independently decreases mouse survival under hypoxia

Although cyclooxygenase (COX) role in cancer angiogenesis has been studied, little is known about its role in brain angioplasticity. In the present study, we chronically infused mice with ketorolac, a non‐specific COX inhibitor that does not cross the blood–brain barrier (BBB), under normoxia or 50% isobaric hypoxia (10% O₂ by volume). Ketorolac increased mortality rate under hypoxia in a dose‐dependent manner. Using in vivo multiphoton microscopy, we demonstrated that chronic COX inhibition completely attenuated brain angiogenic response to hypoxia. Alterations in a number of angiogenic factors that were reported to be COX‐dependent in other models were assayed at 24‐hr and 10‐day hypoxia. Intriguingly, hypoxia‐inducible factor 1 was unaffected under COX inhibition, and vascular endothelial growth factor receptor type 2 (VEGFR2) and C‐X‐C chemokine receptor type 4 (CXCR4) were significantly but slightly decreased. However, a number of mitogen‐activated protein kinases (MAPKs) were significantly reduced upon COX inhibition. We conclude that additional, angiogenic factor‐independent mechanism might contribute to COX role in brain angioplasticity, probably including mitogenic COX effect on endothelium. Our data indicate that COX activity is critical for systemic adaptation to chronic hypoxia, and BBB COX is essential for hypoxia‐induced brain angioplasticity. These data also indicate a potential risk for using COX inhibitors under hypoxia conditions in clinics. Further studies are required to elucidate a complete mechanism for brain long‐term angiogenesis regulation through COX activity.

Targeting the Epithelial-to-Mesenchymal Transition in Cancer Stem Cells for a Better Clinical Outcome of Glioma

Glioma is one of the most common malignant tumors of the central nervous system with a poor prognosis at present due to lack of effective treatment options. Its initiation, migration, and multipotency are affected by cancer stem cell’s transition. Previous studies imply that changes in the cancer stem cells can affect the malignant differentiation of the tumor. We found that the epithelial-to-mesenchymal transition (EMT)-related regulatory pathway is an important target for tumor therapy. In this review, we discuss the transition factor of EMT and 3 specific pathways that affect the EMT of cancer stem cells during tumor development. We conclude that targeting the EMT process of cancer stem cells can be a feasible approach in the treatment of glioma.

2-Methylthio Conversion of N6-Isopentenyladenosine in Mitochondrial tRNAs by CDK5RAP1 Promotes the Maintenance of Glioma-Initiating Cells

2-Methylthio-N⁶-isopentenyl modification of adenosine (ms²i⁶A) is an evolutionally conserved modification found in mitochondrial (mt)-tRNAs. Cdk5 regulatory subunit-associated protein 1 (CDK5RAP1) specifically converts N6-isopentenyladenosine (i⁶A) to ms²i⁶A at position A37 of four mt-DNA-encoded tRNAs, and the modification regulates efficient mitochondrial translation and energy metabolism in mammals. Here, we report that the ms² conversion mediated by CDK5RAP1 in mt-tRNAs is required to sustain glioma-initiating cell (GIC)-related traits. CDK5RAP1 maintained the self-renewal capacity, undifferentiated state, and tumorigenic potential of GICs. This regulation was not related to the translational control of mt-proteins. CDK5RAP1 abrogated the antitumor effect of i⁶A by converting i⁶A to ms²i⁶A and protected GICs from excessive autophagy triggered by i⁶A. The elevated activity of CDK5RAP1 contributed to the amelioration of the tumor-suppressive effect of i⁶A and promoted GIC maintenance. This work demonstrates that CDK5RAP1 is crucial for the detoxification of endogenous i⁶A and that GICs readily utilize this mechanism for survival.

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CDK5RAP1 is required to sustain the growth of GICs through ms² modification of i⁶A

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Deficit of CDK5RAP1 inhibits the growth of GIC through i⁶A accumulation

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CDK5RAP1 detoxifies i⁶A by conversion into ms²i⁶A in the mitochondria of GICs

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Mitochondria serve as antidotal machinery against i⁶A in GICs

New Insights into Mechanisms of Cisplatin Resistance: From Tumor Cell to Microenvironment

Although cisplatin has been a pivotal chemotherapy drug in treating patients with various types of cancer for decades, drug resistance has been a major clinical impediment. In general, cisplatin exerts cytotoxic effects in tumor cells mainly through the generation of DNA-platinum adducts and subsequent DNA damage response. Accordingly, considerable effort has been devoted to clarify the resistance mechanisms inside tumor cells, such as decreased drug accumulation, enhanced detoxification activity, promotion of DNA repair capacity, and inactivated cell death signaling. However, recent advances in high-throughput techniques, cell culture platforms, animal models, and analytic methods have also demonstrated that the tumor microenvironment plays a key role in the development of cisplatin resistance. Recent clinical successes in combination treatments with cisplatin and novel agents targeting components in the tumor microenvironment, such as angiogenesis and immune cells, have also supported the therapeutic value of these components in cisplatin resistance. In this review, we summarize resistance mechanisms with respect to a single tumor cell and crucial components in the tumor microenvironment, particularly focusing on favorable results from clinical studies. By compiling emerging evidence from preclinical and clinical studies, this review may provide insights into the development of a novel approach to overcome cisplatin resistance.