A cisplatin-resistant head and neck cancer cell line with cytoplasmic p53(mut) exhibits ATP-binding cassette transporter upregulation and high glutathione levels

Lipid-Coated Polymeric Nanoparticles for the Photodynamic Therapy of Head and Neck Squamous Cell Carcinomas

Next to alcohol and tobacco abuse, infection with human papillomaviruses (HPVs) is a major risk factor for developing head and neck squamous cell carcinomas (HNSCCs), leading to 350,000 casualties worldwide each year. Limited therapy options and drug resistance raise the urge for alternative methods such as photodynamic therapy (PDT), a minimally invasive procedure used to treat HNSCC and other cancers. We prepared lipid-coated polymeric nanoparticles encapsulating curcumin as the photosensitizer (CUR-LCNPs). The prepared CUR-LCNPs were in the nanometer range (153.37 ± 1.58 nm) and showed an encapsulation efficiency of 92.69 ± 0.03%. Proper lipid coating was visualized using atomic force microscopy (AFM). The CUR-LCNPs were tested in three HPVpos and three HPVneg HNSCC lines regarding their uptake capabilities and in vitro cell killing capacity, revealing a variable but highly significant tumor cell inhibiting effect in all tested HNSCC cell lines. No significant differences were detected between the HPVpos and HPVneg HNSCC groups (mean IC50: (9.34 ± 4.73 µmol/L vs. 6.88 ± 1.03 µmol/L), suggesting CUR-LCNPs/PDT to be a promising therapeutic option for HNSCC patients independent of their HPV status.

M2 tumor-associated macrophage mediates the maintenance of stemness to promote cisplatin resistance by secreting TGF-β1 in esophageal squamous cell carcinoma

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is a deadly gastrointestinal malignancy, and chemotherapy resistance is a key factor leading to its poor prognosis. M2 tumor-associated macrophages (M2-TAMs) may be an important cause of chemoresistance in ESCC, but its exact mechanism is still unclear.

METHODS

In order to study the role of M2-TAMs in ESCC chemoresistance, CCK-8, clone formation assay, flow cytometric apoptosis assay, qRT-PCR, western blotting, and serum-free sphere formation assays were used. In vivo animal experiments and human ESCC tissues were used to confirm the findings.

RESULTS

In vitro and in vivo animal experiments, M2-TAMs reduced the sensitivity of ESCC cells to cisplatin. Mechanistically, M2-TAMs highly secreted TGF-β1 which activated the TGFβR1-smad2/3 pathway to promote and maintain the stemness characteristic of ESCC cells, which could inhibit the sensitivity to cisplatin. Using TGFβ signaling inhibitor SB431542 or knockdown of TGFβR1 could reverse the cisplatin resistance of ESCC cells. In 92 cases of human ESCC tissues, individuals with a high density of M2-TAMs had considerably higher levels of TGF-β1. These patients also had worse prognoses and richer stemness markers.

CONCLUSION

TGF-β1 secreted from M2-TAMs promoted and maintained the stemness characteristic to induce cisplatin resistance in ESCC by activating the TGFβ1-Smad2/3 pathway.

The importin beta superfamily member RanBP17 exhibits a role in cell proliferation and is associated with improved survival of patients with HPV+ HNSCC

Background

More than twenty years after its discovery, the role of the importin beta superfamily member Ran GTP-binding protein (RanBP) 17 is still ill defined. Previously, we observed notable RanBP17 RNA expression levels in head and neck squamous cell carcinoma (HNSCC) cell lines with disruptive TP53 mutations.

Methods

We deployed HNSCC cell lines as well as cell lines from other tumor entities such as HCT116, MDA-MB-231 and H460, which were derived from colon, breast and lung cancers respectively. RNAi was used to evaluate the effect of RanBP17 on cell proliferation. FACS analysis was used for cell sorting according to their respective cell cycle phase and for BrdU assays. Immunocytochemistry was deployed for colocalization studies of RanBP17 with Nucleolin and SC35 (nuclear speckles) domains. TCGA analysis was performed for prognostic assessment and correlation analysis of RanBP17 in HNSCC patients.

Results

RNAi knockdown of RanBP17, significantly reduced cell proliferation in HNSCC cell lines. This effect was also seen in the HNSCC unrelated cell lines HCT116 and MDA-MB-231. Similarly, inhibiting cell proliferation with cisplatin reduced RanBP17 in keratinocytes but lead to induction in tumor cell lines. A similar observation was made in tumor cell lines after treatment with the EGFR kinase inhibitor AG1478. In addition to previous reports, showing colocalization of RanBP17 with SC35 domains, we observed colocalization of RanBP17 to nuclear bodies that are distinct from nucleoli and SC35 domains. Interestingly, for HPV positive but not HPV negative HNSCC, TCGA data base analysis revealed a strong positive correlation of RanBP17 RNA with patient survival and CDKN2A.

Conclusions

Our data point to a role of RanBP17 in proliferation of HNSCC and other epithelial cells. Furthermore, RanBP17 could potentially serve as a novel prognostic marker for HNSCC patients. However, we noted a major discrepancy between RanBP17 RNA and protein expression levels with the used antibodies. These observations could be explained by the presence of additional RanBP17 splice isoforms and more so of non-coding circular RanBP17 RNA species. These aspects need to be addressed in more detail by future studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09854-0.

Activation of ABCC Genes by Cisplatin Depends on the CoREST Occurrence at Their Promoters in A549 and MDA-MB-231 Cell Lines

Simple Summary

Cisplatin resistance is a common issue that affects patients with a variety of cancers who are treated with this drug. In this research, we present a novel epigenetic mechanism that controls the expression of ABC-family transporters, which are involved in multidrug resistance. We report that the CoREST complex may be a key factor that determines the transcription of ABC transporters in non-small cell lung and triple-negative breast cancer cells (A549 and MDA-MB-231, respectively) treated with cisplatin. By occupying gene promoters, this multi-subunit repressor prevents both an EP300-dependent increase in ABCC transcription induced by the alkylating drug and gene overexpression in cisplatin-resistant phenotypes. Moreover, the CoREST-free promoter of ABCC10 responds to cisplatin with EP300-mediated gene activation, which is only possible in p53-proficient cells.

Abstract

Although cisplatin-based therapies are common among anticancer approaches, they are often associated with the development of cancer drug resistance. This phenomenon is, among others, caused by the overexpression of ATP-binding cassette, membrane-anchored transporters (ABC proteins), which utilize ATP to remove, e.g., chemotherapeutics from intracellular compartments. To test the possible molecular basis of increased expression of ABCC subfamily members in a cisplatin therapy mimicking model, we generated two cisplatin-resistant cell lines derived from non-small cell lung cancer cells (A549) and triple-negative breast cancer cells (MDA-MB-231). Analysis of data for A549 cells deposited in UCSC Genome Browser provided evidence on the negative interdependence between the occurrence of the CoREST complex at the gene promoters and the overexpression of ABCC genes in cisplatin-resistant lung cancer cells. Pharmacological inhibition of CoREST enzymatic subunits—LSD1 and HDACs—restored gene responsiveness to cisplatin. Overexpression of CoREST-free ABCC10 in cisplatin-resistant phenotypes was caused by the activity of EP300 that was enriched at the ABCC10 promoter in drug-treated cells. Cisplatin-induced and EP300-dependent transcriptional activation of ABCC10 was only possible in the presence of p53. In summary, the CoREST complex prevents the overexpression of some multidrug resistance proteins from the ABCC subfamily in cancer cells exposed to cisplatin. p53-mediated activation of some ABCC genes by EP300 occurs once their promoters are devoid of the CoREST complex.

The Molecular Basis and Therapeutic Aspects of Cisplatin Resistance in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is a kind of malignant tumors with low survival rate and prone to have early metastasis and recurrence. Cisplatin is an alkylating agent which induces DNA damage through the formation of cisplatin-DNA adducts, leading to cell cycle arrest and apoptosis. In the management of advanced OSCC, cisplatin-based chemotherapy or chemoradiotherapy has been considered as the first-line treatment. Unfortunately, only a portion of OSCC patients can benefit from cisplatin treatment, both inherent resistance and acquired resistance greatly limit the efficacy of cisplatin and even cause treatment failure. Herein, this review outline the underlying mechanisms of cisplatin resistance in OSCC from the aspects of DNA damage and repair, epigenetic regulation, transport processes, programmed cell death and tumor microenvironment. In addition, this review summarizes the strategies applicable to overcome cisplatin resistance, which can provide new ideas to improve the clinical therapeutic outcome of OSCC.

GADD45α alleviates the CDDP resistance of SK-OV3/cddp cells via redox-mediated DNA damage

Epithelial ovarian cancer has the highest mortality rate of all malignant ovarian cancer types. Great progress has been made in the treatment of ovarian cancer in recent years. However, drug resistance has led to a low level of 5-year survival rate of epithelial ovarian cancer, and the molecular mechanism of which remains unknown. The aim of the present study was to identify the role of redox status in the cisplatin (CDDP) resistance of ovarian cancer. CDDP-resistant SK-OV3 (SK-OV3/cddp) cells were prepared and their reactive oxygen species and glutathione levels were investigated. The effects of hydrogen peroxide on the CDDP sensitivity of the SK-OV3/cddp cells and their expression levels of the redox-associated protein growth arrest and DNA damage 45a (GADD45α) were also investigated. In addition, the impact of GADD45α overexpression on cell viability was evaluated in vitro and in vivo, and the levels of Ser-139 phosphorylated H2A histone family member X (γ-H2AX), which is associated with DNA damage, were detected. The results suggested that redox status affected the drug resistance of the ovarian cancer cells by increasing the expression of GADD45α. The overexpression of GADD45α reversed the CDDP resistance of the SK-OV3/cddp cells and increased the level of γ-H2AX. In conclusion, GADD45α alleviated the CDDP resistance of SK-OV3/cddp cells via the induction of redox-mediated DNA damage.

Combined EGFR1 and PARP1 Inhibition Enhances the Effect of Radiation in Head and Neck Squamous Cell Carcinoma Models

Head and neck squamous cell carcinoma (HNSCC) is a challenging cancer with little change in five-year overall survival rate of 50-60% over the last two decades. Radiation with or without platinum-based drugs remains the standard of care despite limited benefit and high toxicity. HNSCCs often overexpress epidermal growth factor receptor (EGFR) and inhibition of EGFR signaling enhances radiation sensitivity by interfering with repair of radiation-induced DNA breaks. Poly (adenosine diphosphate-ribose) polymerase-1 (PARP1) also participates in DNA damage repair, but its inhibition provides benefit in cancers that lack DNA repair by homologous recombination (HR) such as BRCA-mutant breast cancer. HNSCCs in contrast are typically BRCA wild-type and proficient in HR repair, making it challenging to apply anti-PARP1 therapy in this model. A recently published study showed that a combination of EGFR and PARP1 inhibition induced more DNA damage and greater growth control than each single agent in HNSCC cells. This led us to hypothesize that a combination of EGFR and PARP1 inhibition would enhance the efficacy of radiation to a greater extent than each single agent, providing a rationale for paradigm-shifting combinatorial approaches to improve the standard of care in HNSCC. Here, we report a proof-of-concept study using Detroit562 HNSCC cells, which are proficient for DNA repair by both HR and non-homologous end joining (NHEJ) mechanisms. We tested the effect of adding cetuximab and/or olaparib (inhibitors of EGFR and PARP1, respectively) to radiation and compared it to that of cisplatin and radiation combination, which is the standard of care. Our results demonstrate that the combination of cetuximab and olaparib with radiation was superior to the combination of any single drug with radiation in terms of induction of unrepaired DNA damage, induction of senescence, apoptosis and clonogenic death, and tumor growth control in mouse xenografts. Combined with our recently published phase I safety data on cetuximab/olaparib/radiation triple combination, the data reported here demonstrate a potential for combining biologically-based therapies that might optimize radiosensitization in HNSCC.

In Vitro Study of Synergic Effect of Cisplatin and Low Molecular Weight Heparin on Oral Squamous Cell Carcinoma

Objectives

To evaluate the possible synergic effect of cisplatin and low molecular weight heparin (LMWH) on oral squamous cell carcinoma (OSCC).

Materials and Methods

Cisplatin and enoxaparin sodium, alone or in combination, were administered at doses of 1, 2, 4, 8 and 10 µM and 0.1, 0.5, 1, 5, 10, 50, and 100 µg/ml, respectively, to the H357 human OSCC line. The effects on cell viability and apoptosis were evaluated after 24, 48, and 72 h and on cell migration after 18 and 24 h.

Results

10 µM concentration of cisplatin produced the greatest decrease in cell viability, with significant differences at 24 (p=0.009), 48 (p=0.001) and 72 h (p = 0.003); the 100 µg/ml dose of enoxaparin produced the greatest decrease in cell viability but without significant differences (p>0.05). When different concentrations of cisplatin and enoxaparin were combined, it was found that 100 µg/ml enoxaparin sodium produced the greatest synergic effect on cell viability reduction. In analyses of apoptosis and cell migration, it was found that the combination of cisplatin at 8 or 10 μM and 100 μg/ml enoxaparin produced a higher rate of apoptosis at 24, 48, and 72 h and a greater reduction in cell migration at 18 and 24 h.

Conclusions

A combination of cisplatin and enoxaparin sodium shows a synergic effect that reduces cell viability and cell migration capacity and increases the apoptosis of human OSCC cells.

Clinical relevance

Enoxaparin may be beneficial in chemotherapy for patients with OSCC; this finding requires further clinical and laboratory investigation.

Increased ABCC2 expression predicts cisplatin resistance in non-small cell lung cancer

Long-term use of platinum-based drugs can cause non-small cell lung cancer (NSCLC) to develop extremely strong drug resistance. Increasing the drug dosage does not have better treatment effects and could lead to serious complications. High levels of drug resistance are considered to be characteristic of human tumours and are usually mediated by genes related to multidrug resistance. Multidrug resistance-associated protein 2 (ABCC2), an ATP-binding cassette multidrug resistance transporter, was found to be overexpressed in various human cancers. In this study, we found that ABCC2 was also upregulated in cisplatin (DDP)-resistant A549 cells (A549/DDP). Functional studies demonstrated that ABCC2 knockdown reversed DDP resistance and promoted G1 phase arrest in A549/DDP cells, and PARP and caspase-3 were activated in A549/DDP cells following ABCC2 knockdown. In vivo, ABCC2 knockdown enhanced the cytotoxicity of DDP to subcutaneous A549 tumours. Together, these results suggest that ABCC2 may be a potential therapeutic strategy for overcoming DDP resistance in NSCLC patients. SIGNIFICANCE OF THE STUDY: In this study, we investigated the role of ABCC2 in cisplatin resistance of NSCLC cells. Our data show that ABCC2 expression was associated with resistance to cisplatin and that knockdown ABCC2 could reverse cisplatin resistance in NSCLC cells. Taken together, our study suggests that reducing the expression of ABCC2 could become an important strategy for enhancing the sensitivity of NSCLC cells to cisplatin.

EGFR Blockade Reverses Cisplatin Resistance in Human Epithelial Ovarian Cancer Cells

Background:

EOC is one of the most lethal gynecological malignancy worldwide. Although the majority of EOC patients achieve clinical remission after induction therapy, over 80% relapse and succumb to the chemoresistant disease. Previous investigations have demonstrated the association of EGFR with resistance to cytotoxic chemotherapies, hormone therapy, and radiotherapy in the cancers. These studies have highlighted the role of EGFR as an attractive therapeutic target in cisplatin-resistant EOC cells.

Methods:

The human ovarian cell lines (SKOV3 and OVCAR3) were cultured according to ATCC recommendations. The MTT assay was used to determine the chemosensitivity of the cell lines in exposure to cisplatin and erlotinib. The qRT-PCR was applied to analyze the mRNA expression of the desired genes.

Results:

Erlotinib in combination with cisplatin reduced the cell proliferation in the chemoresistant EOC cells in comparison to monotherapy of the drugs (p < 0.05). Moreover, erlotinib/cisplatin combination synergistically decreased the expression of anti-apoptotic and also increased pro-apoptotic genes expression (p < 0.05). Cisplatin alone could increase the expression of MDR genes. The data suggested that EGFR and cisplatin drive chemoresistance in the EOC cells through MEKK signal transduction as well as through EGFR/MEKK pathways in the cells, respectively.

Conclusion:

Our findings propose that EGFR is an attractive therapeutic target in chemoresistant EOC to be exploited in translational oncology, and erlotinib/cisplatin combination treatment is a potential anti-cancer approach to overcome chemoresistance and inhibit the proliferation of the EOC cells.

β-Sitosterol Reverses Multidrug Resistance via BCRP Suppression by Inhibiting the p53-MDM2 Interaction in Colorectal Cancer

Phytosterols are widely present in vegetable oils, nuts, cereal products, fruits, and berries. Phytosterol-induced treatment sensitivity has recently shed light on alleviating multidrug resistance in cancer therapy. Here, we demonstrated that β-sitosterol, the most common dietary phytosterol, recovers oxaliplatin (OXA) sensitivity in drug-resistant colorectal cancer (CRC) cells by inhibiting breast cancer resistance protein (BCRP) expression. We further showed evidence that β-sitosterol could activate p53 by disrupting the p53-MDM2 interaction, leading to an increase in p53 translocation to the nucleus and silencing the nuclear factor-κB (NF-κB) pathway, which is necessary for BCRP expression. Finally, we suggested that the combination of OXA and β-sitosterol has a synergistic tumor suppression effect in vivo using a xenograft mouse model. These results revealed that β-sitosterol is able to mediate the p53/NF-κB/BCRP signaling axis to regulate the response of CRC to chemotherapy. The combined application of β-sitosterol and OXA can be a potential way to improve CRC treatment.

A Novel Multimodal NIR-II Nanoprobe for the Detection of Metastatic Lymph Nodes and Targeting Chemo-Photothermal Therapy in Oral Squamous Cell Carcinoma

Current surgical treatment for oral squamous cell carcinoma (OSCC) must be as precise as possible to fully resect tumors and preserve functional tissues. Thus, it is urgent to develop efficient fluorescent probes to clearly identify tumor delineation, as well as metastatic lymph nodes. Chemo-photothermal therapy combination attracted a growing attention to increase anti-tumor effect in various types of cancer, including OSCC. In the present study, we designed a multimodal NIR-II probe that involves combining photothermal therapy with chemotherapy, imaging OSCC tumors and detecting metastatic lymph nodes. Methods: In this study, we synthesized a novel near infrared (NIR)-II probe named TQTPA [4,4'-((6,7-bis(4-(hexyloxy)phenyl)-[1,2,5]thiadiazolo [3,4-g]quinoxaline-4,9-diyl)bis(thiophene-5,2-diyl))bis(N,N-diphenylaniline)] via the Suzuki reaction and prepared multimodal nanoparticles (NPs) loading TQTPA and cis-dichlorodiammine platinum (CDDP) (HT@CDDP) by hyaluronic acid. The characteristics of the NPs, including their photothermal and imaging capabilities were investigated in vitro and in vivo. Their anti-tumor efficacy was evaluated using orthotopic, tongue tumor-bearing, nude mice. Results: The NPs possessed good stability and water solubility and were pH/hyaluronidase sensitive. The good tissue penetration quality and active targeting ability enabled the NPs to draw the outline of orthotopic tongue tumors and metastatic lymph nodes as small as 1 mm in nude mice by IR-808 under NIR exposure. In vitro and in vivo experiments validated the biocompatibility and low systematic toxicity of the NPs. At the same time, the NPs acted as multimodal therapy agents, combining photothermal therapy with chemotherapy. Conclusion: With a good imaging capability and anti-tumor efficacy, our NPs successfully outlined orthotopic tongue tumors and metastatic lymph nodes as well as enabled chemo-photothermal therapy combination. Our study established a solid foundation for the application of new clinical diagnosis and treatment patterns in the future.

Millepachine showed novel antitumor effects in cisplatin-resistant human ovarian cancer through inhibiting drug efflux function of ATP-binding cassette transporters

Millepachine (MIL), a bioactive natural chalcone from Chinese herbal medicine Millettia pachycarpa Benth, exhibits strong antitumor effects against many human cancer cells both in vitro and in vivo. In this study, we found that MIL significantly inhibited the proliferation of cisplatin-resistant A2780CP cells via inducing obvious G2/M arrest and apoptosis and down-regulating the activity of topoisomerase II protein. We further found that the mechanism by which MIL showed good antitumor effects in cisplatin-resistant human ovarian cancer was associated with inhibiting the expression of ATP-binding cassette transporters in cisplatin-resistant A2780CP cells. Importantly, MIL did not only significantly inhibit the tumor growth in cisplatin-sensitive A2780S xenograft model, with an inhibitory rate of 73.21%, but also inhibited the tumor growth in the cisplatin-resistant A2780CP xenograft model, with an inhibitory rate of 65.68% (p < 0.001 vs. control; p < 0.001 vs. DDP). In addition, MIL did not induce acquired drug resistance in A2780S tumor-bearing mice with an inhibitory rate of 60.03%. The promising in vitro and in vivo performance indicated that MIL exhibited potential significance for drug research and development.

p53 and metabolism: from mechanism to therapeutics

The tumor cell changes itself and its microenvironment to adapt to different situations, including action of drugs and other agents targeting tumor control. Therefore, metabolism plays an important role in the activation of survival mechanisms to keep the cell proliferative potential. The Warburg effect directs the cellular metabolism towards an aerobic glycolytic pathway, despite the fact that it generates less adenosine triphosphate than oxidative phosphorylation; because it creates the building blocks necessary for cell proliferation. The transcription factor p53 is the master tumor suppressor; it binds to more than 4,000 sites in the genome and regulates the expression of more than 500 genes. Among these genes are important regulators of metabolism, affecting glucose, lipids and amino acids metabolism, oxidative phosphorylation, reactive oxygen species (ROS) generation and growth factors signaling. Wild-type and mutant p53 may have opposing effects in the expression of these metabolic genes. Therefore, depending on the p53 status of the cell, drugs that target metabolism may have different outcomes and metabolism may modulate drug resistance. Conversely, induction of p53 expression may regulate differently the tumor cell metabolism, inducing senescence, autophagy and apoptosis, which are dependent on the regulation of the PI3K/AKT/mTOR pathway and/or ROS induction. The interplay between p53 and metabolism is essential in the decision of cell fate and for cancer therapeutics.

Mitochondrial dysfunction enhances cisplatin resistance in human gastric cancer cells via the ROS-activated GCN2-eIF2α-ATF4-xCT pathway

Mitochondrial DNA mutations and defects in mitochondrial enzymes have been identified in gastric cancers, and they might contribute to cancer progression. In previous studies, mitochondrial dysfunction was induced by oligomycin-enhanced chemoresistance to cisplatin. Herein, we dissected the regulatory mechanism for mitochondrial dysfunction-enhanced cisplatin resistance in human gastric cancer cells. Repeated cisplatin treatment-induced cisplatin-resistant cells exhibited high SLC7A11 (xCT) expression, and xCT inhibitors (sulfasalazine or erastin), xCT siRNA, or a GSH synthesis inhibitor (buthionine sulphoximine, BSO) could sensitize these cells to cisplatin. Clinically, the high expression of xCT was associated with a poorer prognosis for gastric cancer patients under adjuvant chemotherapy. Moreover, we found that mitochondrial dysfunction enhanced cisplatin resistance and up-regulated xCT expression, as well as intracellular glutathione (GSH). The xCT inhibitors, siRNA against xCT or BSO decreased mitochondrial dysfunction-enhanced cisplatin resistance. We further demonstrated that the upregulation of the eIF2α-ATF4 pathway contributed to mitochondrial dysfunction-induced xCT expression, and activated eIF2α kinase GCN2, but not PERK, stimulated the eIF2α-ATF4-xCT pathway in response to mitochondrial dysfunction-increased reactive oxygen species (ROS) levels. In conclusion, our results suggested that the ROS-activated GCN2-eIF2α-ATF4-xCT pathway might contribute to mitochondrial dysfunction-enhanced cisplatin resistance and could be a potential target for gastric cancer therapy.

Maintenance of cellular respiration indicates drug resistance in acute myeloid leukemia

Primary resistance to induction therapy is an unsolved clinical problem in acute myeloid leukemia (AML). Here we investigated drug resistance in AML at the level of cellular metabolism in order to identify early predictors of therapeutic response. Using extracellular flux analysis, we compared metabolic drug responses in AML cell lines sensitive or resistant to cytarabine or sorafenib after 24h of drug treatment to a small cell lung cancer (SCLC) cell line exposed to etoposide. Only drug-resistant AML cells maintained oxidative metabolism upon drug exposure while SCLC cells displayed an overall metabolic shift towards glycolysis, i.e. a Warburg effect to escape drug toxicity. Moreover, primary AML blasts displayed very low glycolytic activity, while oxygen consumption was readily detectable, indicating an essential role of oxidative pathways in the bioenergetics of AML blasts. In line with these observations, analysis of the mitochondrial membrane potential using tetramethylrhodamine ethyl ester staining and flow cytometry allowed for clear discrimination between drug sensitive and resistant AML cell line clones and primary blasts after 24h of treatment with cytarabine or sorafenib. Our data reveal a distinct metabolic phenotype of resistant AML cells and suggest that disrupting oxidative metabolism rather than glycolysis may enhance the cytotoxic effects of chemotherapy in AML.

Kinetic Modeling of ABCG2 Transporter Heterogeneity: A Quantitative, Single-Cell Analysis of the Side Population Assay

The side population (SP) assay, a technique used in cancer and stem cell research, assesses the activity of ABC transporters on Hoechst staining in the presence and absence of transporter inhibition, identifying SP and non-SP cell (NSP) subpopulations by differential staining intensity. The interpretation of the assay is complicated because the transporter-mediated mechanisms fail to account for cell-to-cell variability within a population or adequately control the direct role of transporter activity on staining intensity. We hypothesized that differences in dye kinetics at the single-cell level, such as ABCG2 transporter-mediated efflux and DNA binding, are responsible for the differential cell staining that demarcates SP/NSP identity. We report changes in A549 phenotype during time in culture and with TGFβ treatment that correlate with SP size. Clonal expansion of individually sorted cells re-established both SP and NSPs, indicating that SP membership is dynamic. To assess the validity of a purely kinetics-based interpretation of SP/NSP identity, we developed a computational approach that simulated cell staining within a heterogeneous cell population; this exercise allowed for the direct inference of the role of transporter activity and inhibition on cell staining. Our simulated SP assay yielded appropriate SP responses for kinetic scenarios in which high transporter activity existed in a portion of the cells and little differential staining occurred in the majority of the population. With our approach for single-cell analysis, we observed SP and NSP cells at both ends of a transporter activity continuum, demonstrating that features of transporter activity as well as DNA content are determinants of SP/NSP identity.

Differential expression of multidrug resistance‑related proteins in adriamycin‑resistant (pumc‑91/ADM) and parental (pumc‑91) human bladder cancer cell lines

Multidrug resistance (MDR) is the major obstacle to bladder cancer chemotherapy. Several mechanisms have been implicated in the development of MDR, including extrusion of the drug by cell membrane pumps, associated with P‑glycoprotein (P‑gp) and multidrug resistance‑associated protein (MRP); increased DNA damage repair, associated with topoisomerase II (Topo II); suppression of drug‑induced apoptosis, associated with p53; and regulation of cancer cell growth, associated with vascular endothelial growth factor (VEGF). In the present study, the expression levels of these five markers were detected in an adriamycin (ADM)‑resistant human bladder cancer cell line (pumc‑91/ADM) and its parental cell line (pumc‑91), in order to determine which marker is more important, or whether all of them participate in drug resistance. The expression levels of P‑gp, MRP, Topo II, VEGF and p53 were measured in the two cell lines by reverse transcription‑quantitative polymerase chain reaction, western blotting and immunohistochemistry. A significant increase in P‑gp, MRP and VEGF, and a decrease in Topo II mRNA expression were detected in the pumc‑91/ADM drug‑resistant cell line compared with the pumc‑91 cell line; however, no difference in p53 mRNA expression was detected between the cells. In pumc‑91/ADM cells, the protein expression levels of P‑gp and MRP were upregulated, whereas Topo II was significantly decreased. However, no marked differences in p53 or VEGF expression were detected between the two cell lines at the protein level. The cytoplasmic and cell membrane localization of P‑gp and MRP, the cytoplasmic localization of VEGF, and the nuclear localization of p53 and Topo II were confirmed in the two cell lines. The present study detected increased P‑gp and MRP, and reduced Topo II expression in pumc‑91/ADM cells compared with pumc‑91 cells; however, no difference was detected in p53 and VEGF expression between the cell lines. In conclusion, a significant upregulation of MRP and downregulation of Topo II were detected in the ADM‑resistant human bladder cancer cell line (pumc‑91/ADM) compared with in the parental cell line (pumc‑91).

Expression of Cell-Surface Marker ABCB5 Causes Characteristic Modifications of Glucose, Amino Acid and Phospholipid Metabolism in the G3361 Melanoma-Initiating Cell Line

We present a pilot study aimed at determining the effects of expression of ATP-binding cassette member B5 (ABCB5), a previously described marker for melanoma-initiating cells, on cellular metabolism. Metabolic profiles for two groups of human G3361 melanoma cells were compared, i.e. wildtype melanoma cells with intact ABCB5 expression (ABCB5-WT) and corresponding melanoma cell variants with inhibited ABCB5 expression, through shRNA-mediated gene knockdown (ABCB5-KD). A comprehensive metabolomic analysis was performed by using proton and phosphorus NMR spectroscopy of cell extracts to examine water-soluble metabolites and lipids. Parametric and non-parametric statistical analysis of absolute and relative metabolite levels yielded significant differences for compounds involved in glucose, amino acid and phospholipid (PL) metabolism. By contrast, energy metabolism was virtually unaffected by ABCB5 expression. The sum of water-soluble metabolites per total protein was 17% higher in ABCB5-WT vs. ABCB5-KD G3361 variants, but no difference was found for the sum of PLs. Enhanced abundance was particularly pronounced for lactate (+ 23%) and alanine (+ 26%), suggesting an increase in glycolysis and potentially glutaminolysis. Increases in PL degradation products, glycerophosphocholine and glycerophosphoethanolamine (+ 85 and 123%, respectively), and redistributions within the PL pool suggested enhanced membrane PL turnover as a consequence of ABCB5 expression. The possibility of glycolysis modulation by an ABCB5-dependent IL1β-mediated mechanism was supported by functional studies employing monoclonal antibody (mAb)-dependent ABCB5 protein inhibition in wildtype G3361 melanoma cells. Our metabolomic results suggest that the underlying biochemical pathways may offer targets for melanoma therapy, potentially in combination with other treatment forms.

Mutant p53 Gain of Function and Chemoresistance: The Role of Mutant p53 in Response to Clinical Chemotherapy

PURPOSE

To review mechanisms underlying mutant p53 (mutp53) gain of function (GOF) and mutp53-induced chemoresistance, and to investigate the role of mutp53 in response to clinical chemotherapy.

METHODS

We searched the PubMed database for clinical studies from the past decade, including data evaluating the impact of mutp53 in clinical chemotherapy response.

RESULTS

Interactions between mutp53 and transcriptional factors, proteins or DNA structures, as well as epigenetic regulation, contribute to mutp53 GOF. Major mechanisms of mutp53-induced chemoresistance include enhanced drug efflux and metabolism, promoting survival, inhibiting apoptosis, upregulating DNA repair, suppressing autophagy, elevating microenvironmental resistance and inducing a stem-like phenotype. Clinically, mutp53 predicted resistance to chemotherapy in diffuse large B-cell lymphoma, and esophageal and oropharyngeal cancers, but its impact on chronic lymphocytic leukemia was unclear. In bladder cancer, mutp53 did not predict resistance, whereas in some breast and ovarian cancers, it was associated with sensitivity to certain chemotherapeutic agents.

CONCLUSION

mutp53 has an intricate role in the response to clinical chemotherapy and should not be interpreted in isolation. Furthermore, when predicting tumor response to chemotherapy based on the p53 status, the drugs used should also be taken into consideration. These concepts require further investigation.

Dynamic cellular and molecular modulations of diabetes mediated head and neck carcinogenesis

Head and neck squamous cell carcinoma (HNSCC) is one of the most prevalent neoplasms worldwide. While numerous potent dietary insults were considered as oncogenic players for HNSCC development, the impact of metabolic imbalance was less emphasized during HNSCC carcinogenesis. Previous preclinical and epidemiological investigations showed that DM could possibly be correlated with greater incidence and poorer prognosis in HNSCC patients; however, the outcomes from different groups are contradictive and underlying mechanisms remains elusive. In the present study, the changes of cellular malignancy in response to prolonged glucose incubation in HNSCC cells were examined. The results demonstrated that hyperglycemia enhanced HNSCC cell malignancy over time through suppression of cell differentiation, promotion of cell motility, increased resistance to cisplatin, and up-regulation of the nutrient-sensing Akt/AMPK-mTORC1 pathway. Further analysis showed that a more aggressive tongue neoplastic progression was found under DM conditions compared to non-DM state whereas DM pathology led to a higher percentage of cervical lymph node metastasis and poorer prognosis in HNSCC patients. Taken together, the present study confirms that hyperglycemia and DM could enhance HNSCC malignancy and the outcomes are of great benefit in providing better anti-cancer treatment strategy for DM patients with HNSCC.

Investigating a signature of temozolomide resistance in GBM cell lines using metabolomics

Glioblastoma multiforme (GBM) is the most common form of malignant glioma. Current therapeutic approach to treat this malignancy involves a combination of surgery, radiotherapy and chemotherapy with temozolomide. Numerous mechanisms contributing to inherent and acquired resistance to this chemotherapeutic agent have been identified and can lead to treatment failure. This study undertook a metabolomics-based approach to characterize the metabolic profiles observed in temozolomide-sensitive and temozolomide-resistant GBM cell lines as well as in a small sub-set of primary GBM tumors. This approach was also utilized to explore the metabolic changes modulated upon cell treatment with temozolomide and lomeguatrib, an MGMT inhibitor with temozolomide-sensitizing potential. Metabolites previously explored for their potential role in chemoresistance including glucose, citrate and isocitrate demonstrated elevated levels in temozolomide-resistant GBM cells. In addition, a signature of metabolites comprising alanine, choline, creatine and phosphorylcholine was identified as up-regulated in sensitive GBM cell line across different treatments. These results present the metabolic profiles associated with temozolomide response in selected GBM models and propose interesting leads that could be leveraged for the development of therapeutic or diagnostic tools to impact temozolomide response in GBMs.

Biomarkers to assess the efficiency of treatment with platinum-based drugs: what can metallomics add?

Since the approval of cisplatin as an antineoplastic drug, the medical and the scientific communities have been concerned about the side effects of platinum-based drugs, and this has been the dose-limiting factor that leads to reduced treatment efficiency. Another important issue is the intrinsic or acquired resistance of some patients to treatment. Identifying proper biomarkers is crucial in evaluating the efficiency of a treatment, assisting physicians in determining, at early stages, whether or not the patient presents resistance to the drug, minimizing severe side effects, and allowing them to redirect the established course of chemotherapy. A great effort is being made to identify biomarkers that can be used to predict the outcome of the treatment of cancer patients with platinum-based drugs. In this context, the metallomic approach has not yet been used to its full potential. Since the basis of these drugs is platinum, the monitoring of biomarkers containing this metal should be the natural approach to evaluate treatment progress. This review intends to show where the research in this field stands and points out some gaps that can be filled by metallomics.