First-line Chemotherapeutic Agent Research Articles

Unsymmetric Cisplatin-Based Pt(IV) Conjugates Containing a PARP-1 Inhibitor Pharmacophore Tested on Malignant Pleural Mesothelioma Cell Lines.

Cisplatin is widely employed as a first-line chemotherapeutic agent for many solid tumors, including malignant pleural mesothelioma (MPM). However, its clinical use is limited by heavy side effects and acquired resistance, the latter being mainly related to enhanced DNA repair. Many clinical trials using combinations of platinum drugs and PARP-1 inhibitors (PARPis) have been carried out, with the hope that such combinations might lead to improved therapeutic efficacy against tumors. Here, the synthesis and efficacy in reducing MPM cell viability of four cisplatin-based Pt(IV) prodrugs containing the PARPi 3-aminobenzamide (3-ABA) fragment are described. The most promising conjugate is more effective than cisplatin or cisplatin/3-ABA combination, administered in equimolar doses, in inhibiting PARP-1 activity and inducing apoptosis in BRCA1/2 wild type MPM cells, grown as monolayer or as multicellular spheroids.

AGR2-Dependent Nuclear Import of RNA Polymerase II Constitutes a Specific Target of Pancreatic Ductal Adenocarcinoma in the Context of Wild-Type p53

Promoted by pancreatitis, oncogenic KrasG12D triggers acinar cells' neoplastic transformation through acinar-to-ductal metaplasia (ADM) and pancreatic intraepithelial neoplasia. Anterior gradient 2 (Agr2), a known inhibitor of p53, is detected at early stage of pancreatic ductal adenocarcinoma (PDAC) development. RNA polymerase II (RNAPII) is a key nuclear enzyme; regulation of its nuclear localization in mammalian cells represents a potential therapeutic target. A mouse model of inflammation-accelerated KrasG12D-driven ADM and pancreatic intraepithelial neoplasia development was used. Pancreas-specific Agr2 ablation was performed to access its role in pancreatic carcinogenesis. Hydrophobic hexapeptides loaded in liposomes were developed to disrupt Agr2-RNAPII complex. We found that Agr2 is up-regulated in ADM-to-pancreatic intraepithelial neoplasia transition in inflammation and KrasG12D-driven early pancreatic carcinogenesis. Genetic ablation of Agr2 specifically blocks this metaplastic-to-neoplastic process. Mechanistically, Agr2 directs the nuclear import of RNAPII via its C-terminal nuclear localization signal, undermining the ATR-dependent p53 activation in ADM lesions. Because Agr2 binds to the largest subunit of RNAPII in a peptide motif-dependent manner, we developed a hexapeptide to interfere with the nuclear import of RNAPII by competitively disrupting the Agr2-RNAPII complex. This novel hexapeptide leads to dysfunction of RNAPII with concomitant activation of DNA damage response in early neoplastic lesions; hence, it dramatically compromises PDAC initiation invivo. Moreover, the hexapeptide sensitizes PDAC cells and patient-derived organoids harboring wild-type p53 to RNAPII inhibitors and first-line chemotherapeutic agents invivo. Of note, this therapeutic effect is efficient across various cancer types. Agr2 is identified as a novel adaptor protein for nuclear import of RNAPII in mammalian cells. Also, we provide genetic evidence defining Agr2-dependent nuclear import of RNAPII as a pharmaceutically accessible target for prevention and treatment in PDAC in the context of wild-type p53.

Abstract 1422: Neuropilin-2, a potential target against neuroendocrine like therapy resistant prostate cancer

Abstract Background: Prostate cancer (PCa) patient management is becoming increasingly challenging owing to the emergence of advanced therapy-resistant PCa. Published reports from our laboratory demonstrated that neuropilin-2 (NRP2), a non-tyrosine kinase transmembrane receptor, is associated with therapy resistance in aggressive PCa. Such advanced PCa is often associated with diverse genetic changes that complicate the therapeutic interventions. One example is the loss of tumor suppressor gene TP53 along with RB1 to develop therapy resistant neuroendocrine (NE)-like PCa that evades the standard androgen depletion therapy (ADT) and is resistant to first-line chemotherapy. Our results indicate that loss of TP53 and RB1 is associated with significantly increased expression of NRP2. Significance of the problem: Switch to NE-like lineage has been found to be associated with resistance to androgen receptor (AR) targeted therapy as well as chemotherapy. Patients with NE-like PCa show poor prognosis owing to the heterogeneous feature of the tumors and unavailability of effective therapy against this type of cancer. Therefore, identification of potential molecular target(s) is necessary to combat this disease. Objective: The objective of this study is to comprehend the underlying molecular mechanism/s of increased NRP2 expression in PCa, and whether targeting NRP2 would be effective against therapy resistant NE-like PCa, especially in combination with first-line chemotherapeutic agents. Study design: Current study was performed to test the NRP2 status in NE-like PCa cells and to understand if NRP2 is associated with the therapy resistance in this type of aggressive cancer. Moreover, efficacy of NRP2 depletion to sensitize the cancer cells to the chemotherapeutic agents used clinically was evaluated. A stable cell line model of NE-like PCa was developed and characterized by knocking down TP53 and RB1 genes in castration resistant prostate cancer (CRPC) cells. The resistance of the cells against the clinically used chemotherapy was investigated. In addition, efficacy of the chemotherapeutic agents following NRP2 knockdown was evaluated in in-vitro and in-vivo models. For in-vivo studies, PCa bone metastatic mouse model was developed in our laboratory and the effect of the depletion of NRP2 in combination with chemotherapeutic agent was evaluated. Results: NRP2 was significantly expressed in the NE-like PCa cells and knockdown of NRP2 sensitized the originally resistant NE-like cells to chemotherapeutic drugs. Tumor burden was also reduced in the bone metastatic mouse model upon NRP2 depletion when given in combination with chemotherapy. Conclusion: Therefore, targeting NRP2 can be an effective therapeutic strategy to combat highly aggressive and therapy resistant NE-like PCa. Citation Format: Ridwan Islam, Navatha Polavaram, Zhengdong Hong, Sreyashi Bhattacharya, Sanika Bodas, Benjamin Teply, Michael Muders, Kaustubh Datta, Samikshan Dutta. Neuropilin-2, a potential target against neuroendocrine like therapy resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1422.

MiR-454-3p Promotes Oxaliplatin Resistance by Targeting PTEN in Colorectal Cancer.

Colorectal cancer is one of the most common malignancies worldwide. Oxaliplatin is the first-line chemotherapeutic agent for the treatment of advanced colorectal cancer. However, acquired resistance to oxaliplatin limits its therapeutic efficacy, and the underlying mechanism remains largely unclear. In this study, we compared the expression of a panel of microRNAs (miRNAs) between oxaliplatin-sensitive and -resistant HCT-116 colorectal cancer cells. We found that miR-454-3p was significantly up-regulated in oxaliplatin-resistant cells and was the most differently expressed miRNA. Interestingly, we observed that inhibition of miR-454-3p resensitized resistant cells to oxaliplatin and enhanced oxaliplatin-induced cellular apoptosis. Moreover, we determined that miR-454-3p promoted oxaliplatin resistance through targeting PTEN and activating the AKT signaling pathway. In vivo study revealed that overexpression of miR-454-3p decreased the sensitivity of HCT-116 xenograft tumors to oxaliplatin treatment in a mouse model. Clinically, overexpression of miR-454-3p was associated with decreased responsiveness to oxaliplatin-based chemotherapy, as well as a short progression-free survival. Taken together, our study indicated that the expression of miR-454-3p could be used to predict oxaliplatin sensitivity, and targeting miR-454-3p could overcome oxaliplatin resistance in colorectal cancer.

Inhibition of the Notch signaling pathway attenuates progression of cell motility, metastasis, and epithelial-to-mesenchymal transition-like phenomena induced by low concentrations of cisplatin in osteosarcoma

Although advances in osteosarcoma treatment have been made in recent decades, the survival rate for patients suffering from metastatic disease, especially lung metastasis, remains disappointing. Previous studies have confirmed that epithelial-to-mesenchymal transition (EMT) is associated with tumor metastasis, and several studies have suggested that osteosarcoma cells also exhibit EMT-like characteristics. In addition, Notch signaling is known to be related to the development and progression of human malignancies, including osteosarcoma. However, whether chemotherapy affects the EMT-like events and whether these events are medicated by Notch signaling remain to be elucidated. To address these issues, in the current work, osteosarcoma 143B cells were exposed to sublethal concentrations of the first-line chemotherapeutic agent cisplatin (DDP), which promoted cell migration, in vitro invasion, and in vivo lung metastasis. Furthermore, low concentrations of DDP upregulated mesenchymal phenotype-related genes and proteins and promoted EMT-like properties in osteosarcoma cells. In addition, low concentrations of DDP could activate the Notch receptor and its target genes. Finally, combined treatment of DDP with the Notch signaling pathway inhibitor DAPT, which can effectively downregulate mesenchymal phenotype-related genes and proteins, inhibited cell migration and invasion in vitro, and it decreased pulmonary metastatic nodules in vivo. The results of the current study supported the idea that low concentrations of DDP could induce EMT-like characteristics in osteosarcoma cells and could promote cell mobility in vitro, as well as pulmonary metastasis in vivo. Importantly, however, these biological processes are mediated by the Notch signaling pathway. Blocking the Notch signaling pathway can effectively attenuate the osteosarcoma EMT-like phenotype and its associated migration, invasion, and metastasis.

Sequential Release of Pooled siRNAs and Paclitaxel by Aptamer-Functionalized Shell-Core Nanoparticles to Overcome Paclitaxel Resistance of Prostate Cancer.

Paclitaxel (PTX) is a first-line chemotherapeutic agent to treat prostate cancer (PCa), but a large number of patients acquired drug resistance after short-term treatment. To develop combinational therapeutics to overcome PTX-resistant PCa, we established PTX-resistant LNCaP (LNCaP/PTX) cells and found that the LNCaP/PTX cells exhibited epithelial-mesenchymal transition (EMT) and enhanced metastasis during the selection process. We revealed that β-tubulin III, androgen receptor, and CXCR4 expressions were significantly increased in LNCaP/PTX cells and directly contributed to PTX resistance and EMT. Therefore, we developed prostate-specific membrane antigen aptamer (Apt)-functionalized shell-core nanoparticles (PTX/siRNAs NPs-Apt); the hydrophobic DSPE encapsulating PTX formed the dense inner core and the hydrophilic Apt-PEG2K with calcium phosphate (CaP) absorbing siRNAs formed the outer shell to sequentially release siRNAs and PTX, where CaP could trigger lysosomal escape to ensure that pooled siRNAs efficiently released into the cytoplasm to reverse EMT and resensitize PTX, while the PTX located in the core was subsequently released to exert the killing effect of chemotherapy to achieve the best synergistic effect. PTX/siRNAs NPs-Apt showed an enhanced tumor-targeting ability and achieved superior efficacy in the subcutaneous and orthotopic PCa tumor model with minimal side effects.

Emerging Pharmacological and Non-Pharmacological Therapeutics for Prevention and Treatment of Chemotherapy-Induced Peripheral Neuropathy

Simple SummaryChemotherapy-induced peripheral neuropathy (CIPN) is a common and persistent complication of commonly used chemotherapy drugs. This article provides an overview of emerging therapeutics for the prevention and treatment of CIPN and focuses on pharmacological strategies that are derived from novel mechanistic insights and have the potential to be translated into clinically beneficial approaches. It is our contention to call for fostering collaboration between basic and clinical researchers to improve the development of effective strategies.Chemotherapy-induced peripheral neuropathy (CIPN) is a common adverse event of several first-line chemotherapeutic agents, including platinum compounds, taxanes, vinca alkaloids, thalidomide, and bortezomib, which negatively affects the quality of life and clinical outcome. Given the dearth of effective established agents for preventing or treating CIPN, and the increasing number of cancer survivors, there is an urgent need for the identification and development of new, effective intervention strategies that can prevent or mitigate this debilitating side effect. Prior failures in the development of effective interventions have been due, at least in part, to a lack of mechanistic understanding of CIPN and problems in translating this mechanistic understanding into testable hypotheses in rationally-designed clinical trials. Recent progress has been made, however, in the pathogenesis of CIPN and has provided new targets and pathways for the development of emerging therapeutics that can be explored clinically to improve the management of this debilitating toxicity. This review focuses on the emerging therapeutics for the prevention and treatment of CIPN, including pharmacological and non-pharmacological strategies, and calls for fostering collaboration between basic and clinical researchers to improve the development of effective strategies.

Tumor-Associated Macrophages Promote Oxaliplatin Resistance via METTL3-Mediated m6A of TRAF5 and Necroptosis in Colorectal Cancer.

As a third-generation platinum drug, oxaliplatin (OX) is widely used as the first-line chemotherapeutic agent in the treatment of colorectal cancer (CRC). CRC cells acquire resistance to chemotherapy and develop resistance, which is a major challenge for the treatment of advanced CRC. Recent studies have suggested that the therapeutic resistance of tumors is affected by the tumor microenvironment (TME). As a critical role among TME, tumor-associated macrophages (TAMs) play an important role. However, their regulatory mechanism underlying the drug resistance in CRC remains largely unknown. In the present study, we found that the density of macrophages infiltrated into the CRC tissues from OX-resistant patients was significantly higher compared with the OX-sensitive patients. Interestingly, both the total N6-methyladenosine (m6A) RNA content and the expression of its critical methyltransferase METTL3 were increased in the CRC tissues from OX-resistant patients compared with the OX-sensitive patients. Furthermore, we demonstrated that the M2-polarized TAMs enabled the OX resistance via the elevation of METTL3-mediated m6A modification in cells. Through whole-genome CRISPR screening and further validation, we found that TRAF5 contributes to the METTL3-triggered OX resistance in CRC cells. This study unveiled that M2-TAMs were important mediators for the acquisition of OX resistance. Furthermore, we provided evidence that targeting of M2-TAMs and METTL3-mediated m6A modification might be a promising adjuvant therapeutic strategy for CRC patients, especially for OX-resistant CRC patients.

Amlexanox Enhances Temozolomide-Induced Antitumor Effects in Human Glioblastoma Cells by Inhibiting IKBKE and the Akt-mTOR Signaling Pathway.

Temozolomide (TMZ), as the first-line chemotherapeutic agent for the treatment of glioblastoma multiforme (GBM), often fails to improve the prognosis of GBM patients due to the quick development of resistance. The need for more effective management of GBM is urgent. The aim of this study is to evaluate the efficacy of combined therapy with TMZ and amlexanox, a selective inhibitor of IKBKE, for GBM. We found that the combined treatment resulted in significant induction of cellular apoptosis and the inhibition of cell viability, migration, and invasion in primary glioma cells and in the human glioma cell line, U87 MG. As expected, TMZ enhanced the expression of p-AMPK and amlexanox led to the reduction of IKBKE, with no impact on p-AMPK. Furthermore, we demonstrated that compared to other groups treated with each component alone, TMZ combined with amlexanox effectively reversed the TMZ-induced activation of Akt and inhibited the phosphorylation of mTOR. In addition, the combination treatment also clearly reduced in vivo tumor volume and prolonged median survival time in the xenograft mouse model. These results suggest that amlexanox sensitized the primary glioma cells and U87 MG cells to TMZ at least partially through the suppression of IKBKE activation and the attenuation of TMZ-induced Akt activation. Overall, combined treatment with TMZ and amlexanox may provide a promising possibility for improving the prognosis of glioblastoma patients in clinical practice.

Cordycepin Reverses Cisplatin Resistance in Non-small Cell Lung Cancer by Activating AMPK and Inhibiting AKT Signaling Pathway.

Cisplatin (DDP) is the first-line chemotherapeutic agent against lung cancer. However, the therapeutic effect of DDP loses over time due to the acquired drug resistance in non-small cell lung cancer (NSCLC) cells. In recent years, the role of the traditional Chinese medicine (TCM) cordycepin (Cor) in cancer treatment has been attracting attention. However, the effects of Cor on DDP resistance in NSCLC are unclear. In the present study, we aimed to investigate the effects of Cor in combination with DDP on cell proliferation and apoptosis in NSCLC and explore possible underlying mechanisms. The cell proliferation and apoptosis were analyzed in NSCLC parental (A549) and DDP-resistant (A549DDP) cells treated with DDP alone or in combination with Cor both in vitro and in vivo. Different genes and signaling pathways were investigated between DDP-sensitive and DDP-resistant A549 cells by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The perturbations of the MAPK and PI3K-AKT signaling pathways were evaluated by Western blot analysis. Our data showed that Cor markedly enhanced DDP inhibition on cell proliferation and promotion of apoptosis compared to the DDP-alone group in both A549 and A549DDP cells. The synergic actions were associated with activation of AMPK; inhibition of AKT, mTOR, and downstream P709S6K; and S6 phosphorylation in the AKT pathway compared with DDP alone. Collectively, combination of Cor and DDP has a synergistic effect in inhibiting proliferation and promoting apoptosis of NSCLC cells in the presence or absence of DDP resistance. The antitumor activity is associated with activation of AMPK and inhibition of the AKT pathway to enhance DDP inhibition on NSCLC. Our results suggested that Cor in combination with DDP could be an additional therapeutic option for the treatment of DDP-resistant NSCLC.

New Protein-Coated Silver Nanoparticles: Characterization, Antitumor and Amoebicidal Activity, Antiproliferative Selectivity, Genotoxicity, and Biocompatibility Evaluation.

Nanomaterials quickly evolve to produce safe and effective biomedical alternatives, mainly silver nanoparticles (AgNPs). The AgNPs’ antibacterial, antiviral, and antitumor properties convert them into a recurrent scaffold to produce new treatment options. This work reported the full characterization of a highly biocompatible protein-coated AgNPs formulation and their selective antitumor and amoebicidal activity. The protein-coated AgNPs formulation exhibits a half-inhibitory concentration (IC50) = 19.7 µM (2.3 µg/mL) that is almost 10 times more potent than carboplatin (first-line chemotherapeutic agent) to inhibit the proliferation of the highly aggressive human adenocarcinoma HCT-15. The main death pathway elicited by AgNPs on HCT-15 is apoptosis, which is probably stimulated by reactive oxygen species (ROS) overproduction on mitochondria. A concentration of 111 µM (600 µg/mL) of metallic silver contained in AgNPs produces neither cytotoxic nor genotoxic damage on human peripheral blood lymphocytes. Thus, the AgNPs formulation evaluated in this work improves both the antiproliferative potency on HCT-15 cultures and cytotoxic selectivity ten times more than carboplatin. A similar mechanism is suggested for the antiproliferative activity observed on HM1-IMSS trophozoites (IC50 = 69.2 µM; 7.4 µg/mL). There is no change in cell viability on mice primary cultures of brain, liver, spleen, and kidney exposed to an AgNPs concentration range from 5.5 µM to 5.5 mM (0.6 to 600 µg/mL). The lethal dose was determined following the OECD guideline 420 for Acute Oral Toxicity Assay, obtaining an LD50 = 2618 mg of Ag/Kg body weight. All mice survived the observational period; the histopathology and biochemical analysis show no differences compared with the negative control group. In summary, all results from toxicological evaluation suggest a Category 5 (practically nontoxic) of the Globally Harmonized System of Classification and Labelling of Chemicals for that protein-coated AgNPs after oral administration for a short period and urge the completion of its preclinical toxicological profile. These findings open new opportunities in the development of selective, safe, and effective AgNPs formulations for the treatment of cancer and parasitic diseases with a significant reduction of side effects.

Superior in vitro anticancer effect of biomimetic paclitaxel and triptolide co-delivery system in gastric cancer.

As a well-known anticancer drug, paclitaxel (PTX), a first-line chemotherapeutic agent, remains unsatisfactory for gastric cancer therapy. It is reported that triptolide (TPL) could enhance the anti-gastric cancer effect of PTX. Considering the poor solubility of both drugs, we developed a red blood cell membrane-biomimetic nanosystem, an emerging tool in drug delivery, to co-load paclitaxel and triptolide (red blood cell membrane coated PTX and TPL co-loaded poly(lactic-co-glycolic acid) [PLGA] nanoparticles, RP(P/T)). The successful preparation was confirmed in terms of particle size, morphology, and surface markers assays. This biomimetic system could prolong circulation and escape immune surveillance. And these properties were verified by stability, in vitro drug release, and cellular uptake assays. Moreover, the MTT and colony formation assays demonstrated the superior anti-proliferation effect of the RP(P/T) to free drugs. The enhanced antitumor effects of RP(P/T) on migration and invasion were also evaluated by wound-healing and transwell assays. Overall, the bionic co-delivery nanoplatform with improved efficacy in vitro is a promising therapy for gastric cancer.

Mitochondrial Dynamics Mediated by DRP1 and MFN2 Contributes to Cisplatin Chemoresistance in Human Ovarian Cancer SKOV3 cells.

Cisplatin (DDP) is the first-line chemotherapeutic agent for ovarian cancer. However, the development of DDP resistance seriously influences the chemotherapeutic effect and prognosis of ovarian cancer. It was reported that DDP can directly impinge on the mitochondria and activate the intrinsic apoptotic pathway. Herein, the role of mitochondrial dynamics in DDP chemoresistance in human ovarian cancer SKOV3 cells was investigated. In DDP-resistant SKOV3/DDP cells, mitochondrial fission protein DRP1 was down-regulated, while mitochondrial fusion protein MFN2 was up-regulated. In accordance with the expression of DRP1 and MFN2, the average mitochondrial length was significantly increased in SKOV3/DDP cells. In DDP-sensitive parental SKOV3 cells, downregulation of DRP1 and upregulation of mitochondrial fusion proteins including MFN1,2 and OPA1 occurred at day 2~6 under cisplatin stress. Knockdown of DRP1 or overexpression of MFN2 promoted the resistance of SKOV3 cells to cisplatin. Intriguingly, weaker migration capability and lower ATP level were detected in SKOV3/DDP cells. Respective knockdown of DRP1 in parental SKOV3 cells or MFN2 in SKOV3/DDP cells using siRNA efficiently reversed mitochondrial dynamics, migration capability and ATP level. Moreover, MFN2 siRNA significantly aggravated the DDP-induced ROS production, mitochondrial membrane potential disruption, expression of pro-apoptotic protein BAX and Cleaved Caspase-3/9 in SKOV3/DDP cells. In contrast, DRP1 siRNA alleviated DDP-induced ROS production, mitochondrial membrane potential disruption, expression of pro-apoptotic protein BAX and Cleaved Caspase-3/9 in SKOV3 cells. Thus, these results indicate that mitochondrial dynamics mediated by DRP1 and MFN2 contributes to the development of DDP resistance in ovarian cancer cells, and will also provide a new strategy to prevent chemoresistance in ovarian cancer by targeting mitochondrial dynamics.

Role of HMGB1 in Chemotherapy-Induced Peripheral Neuropathy.

Chemotherapy-induced peripheral neuropathy (CIPN), one of major dose-limiting side effects of first-line chemotherapeutic agents such as paclitaxel, oxaliplatin, vincristine, and bortezomib is resistant to most of existing medicines. The molecular mechanisms of CIPN have not been fully understood. High mobility group box 1 (HMGB1), a nuclear protein, is a damage-associated molecular pattern protein now considered to function as a pro-nociceptive mediator once released to the extracellular space. Most interestingly, HMGB1 plays a key role in the development of CIPN. Soluble thrombomodulin (TMα), known to degrade HMGB1 in a thrombin-dependent manner, prevents CIPN in rodents treated with paclitaxel, oxaliplatin, or vincristine and in patients with colorectal cancer undergoing oxaliplatin-based chemotherapy. In this review, we describe the role of HMGB1 and its upstream/downstream mechanisms in the development of CIPN and show drug candidates that inhibit the HMGB1 pathway, possibly useful for prevention of CIPN.

DDRE-28. EGFR INHIBITION DOWNREGULATES MGMT AND SENSITIZES GBM CELLS TO TMZ

Abstract Glioblastoma (GBM) is a highly malignant type of adult brain tumor with a poor prognosis. Temozolomide (TMZ), a DNA alkylating agent, has been widely used as an effective first-line chemotherapeutic agent for the treatment of GBM patients. The efficacy of TMZ in GBM depends on the absence of the DNA repair protein MGMT which reverses the DNA damage induced by TMZ. The MGMT promoter is hypermethylated in about 45% of GBMs, resulting in lack of MGMT expression and increased responsiveness to TMZ. TMZ is less effective in MGMT unmethylated GBMs. We propose that EGFR inhibition downregulates MGMT and sensitizes glioma cells to TMZ and a combination of pretreatment with erlotinib followed by TMZ could be a useful therapeutic approach in MGMT expressing GBMs. As our experimental model we used multiple MGMT unmethylated lines from the Mayo Clinic patient derived xenografts (PDXs) panel. Our data demonstrate that exposure of cells to EGFR tyrosine kinase inhibitor erlotinib for 48h results in downregulation of MGMT at the mRNA and protein level. Additionally, EGFR inhibition activates the AP-1 transcription factor and overexpression of AP-1 components Fos and Jun results in decreased MGMT expression in TMZ resistant PDXs, suggesting that AP-1 acts as a transcriptional repressor of MGMT. We further identified that the mice implanted with TMZ resistant PDXs pretreated with afatinib followed by TMZ treatment survived longer compared to those treated with TMZ alone. Thus, the use of EGFR inhibition may enhance the sensitivity of MGMT unmethylated GBMs to TMZ.

Design, synthesis and biological evaluation of novel 1,3,4-thiadiazole derivatives as anti-glioblastoma agents targeting the AKT pathway

In spite of progress in understanding biology of glioblastoma (GBM), this tumor remains incurable with a median survival rate of 15 months. Previous studies have shown that 2-(4-fluorophenyloamino)-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole (FPDT) and 2-(3-chlorophenyloamino)-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole (CPDT) diminished viability of cancer cell lines of different origin. In the current study, we have examined activity of these compounds in several GBM cell lines and patient-derived GBM cells. We have also designed, synthesized and evaluated anti-GBM activity of novel 1,3,4-thiadiazole derivatives containing additional Cl or CH2CH3 substitute at C5-position of 2,4-dihydroxyphenyl. The tested compounds presented a considerable cytotoxicity against all GBM cell lines examined as well as patient-derived GBM cells. They were 15–110 times more potent than temozolomide, the first-line chemotherapeutic agent for GBM. Notably, in anticancer concentrations three of the derivatives were not toxic to human astrocytes. FPDT appeared to be the most promising compound with IC50 values between 45 μM and 68 μM for GBM cells and >100 μM for astrocytes. It augmented activity of temozolomide and inhibited proliferation migration and invasion of GBM cells. Treatment with FPDT diminished phosphorylation level of GSK3β and AKT. Pretreatment with PDGF-BB, an AKT activator, partially protected cells from death caused by FPDT, indicating that FPDT-mediated decrease in cell viability is causatively related to the inhibition of the AKT pathway.

Cedrol, a Sesquiterpene Alcohol, Enhances the Anticancer Efficacy of Temozolomide in Attenuating Drug Resistance via Regulation of the DNA Damage Response and MGMT Expression.

Glioblastoma (GBM) is a common and aggressive brain tumor with a median survival of 12-15 months. Temozolomide (TMZ) is a first-line chemotherapeutic agent used in GBM therapy, but the occurrence of drug resistance limits its antitumor activity. The natural compound cedrol has remarkable antitumor activity and is derived from Cedrus atlantica. In this study, we investigated the combined effect of TMZ and cedrol in GBM cells in vitro and in vivo. The TMZ and cedrol combination treatment resulted in consistently higher suppression of cell proliferation via regulation of the AKT and MAPK signaling pathways in GBM cells. The combination treatment induced cell cycle arrest, cell apoptosis, and DNA damage better than either drug alone. Furthermore, cedrol reduced the expression of proteins associated with drug resistance, including O6-methlyguanine-DNA-methyltransferase (MGMT), multidrug resistance protein 1 (MDR1), and CD133 in TMZ-treated GBM cells. In the animal study, the combination treatment significantly suppressed tumor growth through the induction of cell apoptosis and decreased TMZ drug resistance. Moreover, cedrol-treated mice exhibited no significant differences in body weight and improved TMZ-induced liver damage. These results imply that cedrol may be a potential novel agent for combination treatment with TMZ for GBM therapy that deserves further investigation.

Combining PARP Inhibition with Platinum, Ruthenium or Gold Complexes for Cancer Therapy.

Platinum drugs are heavily used first‐line chemotherapeutic agents for many solid tumours and have stimulated substantial interest in the biological activity of DNA‐binding metal complexes. These complexes generate DNA lesions which trigger the activation of DNA damage response (DDR) pathways that are essential to maintain genomic integrity. Cancer cells exploit this intrinsic DNA repair network to counteract many types of chemotherapies. Now, advances in the molecular biology of cancer has paved the way for the combination of DDR inhibitors such as poly (ADP‐ribose) polymerase (PARP) inhibitors (PARPi) and agents that induce high levels of DNA replication stress or single‐strand break damage for synergistic cancer cell killing. In this review, we summarise early‐stage, preclinical and clinical findings exploring platinum and emerging ruthenium anti‐cancer complexes alongside PARPi in combination therapy for cancer and also describe emerging work on the ability of ruthenium and gold complexes to directly inhibit PARP activity.

Exploring Specific miRNA-mRNA Axes With Relationship to Taxanes-Resistance in Breast Cancer

Breast cancer is the most prevalent type of malignancy in women worldwide. Taxanes (paclitaxel and docetaxel) are widely applied as first-line chemotherapeutic agents, while the therapeutic effect is seriously limited by the development of drug resistance. In the present study, we screened out several miRNAs dysregulated in taxanes-resistant breast cancer samples and confirmed that two miRNAs (miR-335-5p and let-7c-5p) played a major role in cell proliferation, apoptosis, and chemo-resistance. In addition, the weighted gene co-expression network analysis (WGCNA) for potential target genes of miR-335-5p and let-7c-5p identified three hub genes (CXCL9, CCR7, and SOCS1) with a positive relationship to taxanes-sensitivity. Further, target relationships between miR-335-5p and CXCL9, let-7c-5p and CCR7/SOCS1 were confirmed by dual-luciferase reporter assays. Importantly, the regulatory functions of CXCL9, CCR7, and SOCS1 on proliferation and chemoresistance were validated. In conclusion, our study shed light on clinical theragnostic relationships between miR-335-5p/CXCL9, let-7c-5p/CCR7/SOCS1 axes, and taxanes-resistance in breast cancer.

MicroRNA-191 modulates cisplatin-induced DNA damage response by targeting RCC2.

Cisplatin is a first-line chemotherapeutic agent for the treatment of many types of cancer, but the emergence of chemoresistance hinders its application. Thus, a better understanding of cisplatin-induced DNA damage response (DDR) would help to overcome this problem. Previously, we have identified a panel of microRNAs with altered expression after cisplatin treatment in HeLa cells. In the current study, we focused on one of them, miR-191, and investigated its function in cisplatin-induced DDR. We found that overexpression of miR-191 sensitized HeLa cells to the cytotoxic effects of cisplatin, resulted in decreased viable cells. However, overexpression of miR-191 did not cause changes in apoptotic cell ratio but rather induced significant G2/M arrest in HeLa cell treated with cisplatin. Additionally, enhanced cisplatin-induced DNA damage was observed. Through bioinformatic analysis and verified by dual-luciferase assay, it was demonstrated that the chromosome condensation 2 regulator (RCC2) gene is a target for miR-191 regulation. Furthermore, the downregulation of RCC2 by siRNA mimics the effects of miR-191, in which greater DNA damage was observed upon cisplatin treatment. Taken together, our study indicates that miR-191 may be an important player in cisplatin-induced DDR, and it elicits its function, at least partially, through the regulation of RCC2.