Pemetrexed acts as an antimyeloma agent by provoking cell cycle blockade and apoptosis

Identification of COQ2 as a regulator of proliferation and lipid peroxidation through genome-scale CRISPR-Cas9 screening in myeloma cells

Multiple myeloma (MM) is the second most common malignant haematological disease with a poor prognosis. The limit therapeutic progress has been made in MM patients with cancer relapse, necessitating deeper research into the molecular mechanisms underlying its occurrence and development. A genome-wide CRISPR-Cas9 loss-of-function screening was utilized to identify potential therapeutic targets in our research. We revealed that COQ2 plays a crucial role in regulating MM cell proliferation and lipid peroxidation (LPO). Knockout of COQ2 inhibited cell proliferation, induced cell cycle arrest and reduced tumour growth in vivo. Mechanistically, COQ2 promoted the activation of the MEK/ERK cascade, which in turn stabilized and activated MYC protein. Moreover, we found that COQ2-deficient MM cells increased sensitivity to the LPO activator, RSL3. Using an inhibitor targeting COQ2 by 4-CBA enhanced the sensitivity to RSL3 in primary CD138+ myeloma cells and in a xenograft mouse model. Nevertheless, co-treatment of 4-CBA and RSL3 induced cell death in bortezomib-resistant MM cells. Together, our findings suggest that COQ2 promotes cell proliferation and tumour growth through the activation of the MEK/ERK/MYC axis and targeting COQ2 could enhance the sensitivity to ferroptosis in MM cells, which may be a promising therapeutic strategy for the treatment of MM patients.

Folate metabolism: a re-emerging therapeutic target in haematological cancers

Folate-mediated one carbon (1C) metabolism supports a series of processes that are essential for the cell. Through a number of interlinked reactions happening in the cytosol and mitochondria of the cell, folate metabolism contributes to de novo purine and thymidylate synthesis, to the methionine cycle and redox defence. Targeting the folate metabolism gave rise to modern chemotherapy, through the introduction of antifolates to treat paediatric leukaemia. Since then, antifolates, such as methotrexate and pralatrexate have been used to treat a series of blood cancers in clinic. However, traditional antifolates have many deleterious side effects in normal proliferating tissue, highlighting the urgent need for novel strategies to more selectively target 1C metabolism. Notably, mitochondrial 1C enzymes have been shown to be significantly upregulated in various cancers, making them attractive targets for the development of new chemotherapeutic agents. In this article, we present a detailed overview of folate-mediated 1C metabolism, its importance on cellular level and discuss how targeting folate metabolism has been exploited in blood cancers. Additionally, we explore possible therapeutic strategies that could overcome the limitations of traditional antifolates.

Intrathecal pemetrexed combined with involved-field radiotherapy as a first-line intra-CSF therapy for leptomeningeal metastases from solid tumors: a phase I/II study

Purpose:

A phase I/II study of intrathecal pemetrexed (IP) combined with involved-field radiotherapy (IFRT) was performed to determine feasibility, safety, and antitumor activity for leptomeningeal metastases (LM) from solid tumors.

Methods:

Participants first received induction IP administration, followed by concomitant radiotherapy within 3 days. The concomitant regimen consisted of IP (pemetrexed 10 mg, dexamethasone 5 mg, once per week, 4 times in 4 weeks) and IFRT (40 Gy in 20 fractions). Six participants were recruited to assess feasibility in phase I, and then 28 patients were recruited further. All patients were assessed to investigate safety, efficacy, and outcomes.

Results:

Between April 2018 and December 2018, 34 patients (male: 15; female: 19; median age: 56 years) were enrolled, including non-small-cell lung cancer (21), small-cell lung cancer (5), breast cancer (4), and others (4). Thirty-two patients received concurrent therapy and 25 (74%) patients completed the treatment. Major adverse events (AEs) consisted of myelosuppression, the elevation of hepatic aminotransferases, and radiculitis. Total AEs rate was 53% (18/34), including 6 (18%) patients with grade 3 and 1 (3%) with grade 4 AEs. The response rate was 68% (23/34). The median overall survival was 5.5 (0.3–16.6) months. Median neurological progression-free survival (NPFS) was 3.5 (0.3–15.2) months. Six-month NPFS rate was 47%. One-year survival rate was 21.6%.

Conclusion:

IP at a 10 mg dose on a schedule of 1–2 times per week presented good efficacy and safety in CSF. The concomitant regimen is an efficacious therapeutic option for LM patients with solid tumors.

Trial Registration:

This study (IPLM) was registered at https://register.clinicaltrials.gov [ClinicalTrials.gov identifier: NCT03507244].

The anti-tumor activity of pralatrexate (PDX) correlates with the expression of RFC and DHFR mRNA in preclinical models of multiple myeloma

Multiple myeloma (MM) is the second most common hematologic malignancy. While major advances have been made in the disease, it is still incurable. Although antifolate-based drugs are not commonly used to treat myeloma, new generation analogs with distinct patterns of preclinical and clinical activity may offer an opportunity to identify new classes of potentially active drugs. Pralatrexate (PDX), which was approved for the treatment of relapsed or refractory peripheral T-cell lymphoma in 2009, may be one such drug. Pralatrexate exhibits a potency and pattern of activity distinct from its predecessors like methotrexate (MTX). We sought to understand the activity and mechanisms of resistance of multiple myeloma to these drugs, which could also offer potential strategies for selective use of the drug. We demonstrate that PDX and MTX both induce a significant decrease in cell viability in the low nanomolar range, with PDX exhibiting a more potent effect. We identified a series of myeloma cell lines exhibiting markedly different patterns of sensitivity to the drugs, with some lines frankly resistant, and others exquisitely sensitive. These differences were largely attributed to the basal RFC (Reduced Folate Carrier) mRNA expression levels. RFC mRNA expression correlated directly with rates of drug uptake, with the most sensitive lines exhibiting the most significant intracellular accumulation of pralatrexate. This mechanism explains the widely varying patterns of sensitivity and resistance to pralatrexate in multiple myeloma cell lines. These findings could have implications for this class of drugs and their role in the treatment of multiple myeloma.

Cell Size-Based Decision-Making of a Viral Gene Circuit

Latently infected T cells able to reinitiate viral propagation throughout the body remain a major barrier to curing HIV. Distinguishing between latently infected cells and uninfected cells will advance efforts for viral eradication. HIV decision-making between latency and active replication is stochastic, and drug cocktails that increase bursts of viral gene expression enhance reactivation from latency. Here, we show that a larger host-cell size provides a natural cellular mechanism for enhancing burst size of viral expression and is necessary to destabilize the latent state and bias viral decision-making. Latently infected Jurkat and primary CD4+ T cells reactivate exclusively in larger activated cells, while smaller cells remain silent. In addition, reactivation is cell-cycle dependent and can be modulated with cell-cycle-arresting compounds. Cell size and cell-cycle dependent decision-making of viral circuits may guide stochastic design strategies and applications in synthetic biology and may provide important determinants to advance diagnostics and therapies.

Bohn-Wippert et al. investigate reactivation of T cells latently infected with HIV. They discover that only larger cells exit latency, while smaller cells remain silent. Viral expression bursts are cell size and cell-cycle dependent, presenting dynamic cell states, capable of active control, as sources of viral fate determination.

Accumulated cytotoxicity of CDK inhibitor dinaciclib with first-line chemotherapy drugs in salivary adenoid cystic carcinoma cells

Adenoid cystic carcinoma (ACC) is one of the most common salivary gland malignant tumors. Its treatment failure is partly due to the limitations of chemotherapeutic agents and their adverse effects. The objective of this study was to determine the potential additive anti-cancer effect of a novel CDK inhibitor dinaciclib with first-line chemotherapy drugs in ACC. Protein expression of phosphorylated CDK2 (p-CDK2) in paraffin-embedded tissue specimens of ACC from 17 patients was investigated by immunohistochemistry (IHC). Cell Counting Kit (CCK-8), clone formation assay, and flow cytometry were used to test the proliferation and apoptosis of ACC-2 cells treated with dinaciclib with or without other first-line chemotherapy drugs. Protein expression was also determined by Western blot. Interestingly, we discovered that p-CDK2 protein was expressed in both cytoplasmic and nucleus in salivary ACC tissues, which was higher than that in normal salivary tissues, indicating that agents targeting CDK2 may be potential therapeutic strategies against this type of tumor. As expected, CDK inhibitor dinaciclib significantly induced ACC-2 cells apoptosis. Moreover, it sensitized cells to the chemotherapeutic agents such as cisplatin, pemetrexed, and etoposide (VP-16), and this effect by dinaciclib may induce cell cycle arrest via abrogating CDK2 activity. Therefore, combinational therapy of CDK inhibitor dinaciclib with first-line chemotherapy drugs may be a promising strategy in the treatment of salivary ACC.

Synergistic anti-tumor effect of bullfrog sialic acid-binding lectin and pemetrexed in malignant mesothelioma

Malignant mesothelioma is an aggressive cancer with limited therapeutic options. Sialic acid-binding lectin isolated from Rana catesbeiana oocytes (cSBL) is a multifunctional protein with anti-cancer activity. The effects of pemetrexed, cisplatin, and cSBL were evaluated in mesothelioma and normal mesothelial cell lines. We evaluated cytotoxicity, apoptosis, caspase-3 cleavage and activation, cell proliferation, cell cycle arrest, and levels of cell cycle proteins in H28 cells treated with pemetrexed, cisplatin, and cSBL alone or in combination. Treatment with cSBL alone was cytotoxic to mesothelioma cells. The anti-cancer effect of cSBL was observed in a broader range of cell lines and exhibited greater cancer cell selectivity than pemetrexed or cisplatin. Combination treatment with pemetrexed + cSBL resulted in greater dose-dependent cytotoxicity than pemetrexed + cisplatin, the standard of care in mesothelioma. The synergistic effect of pemetrexed + cSBL was mediated by the cytostatic effect of pemetrexed and the cytotoxic effect of cSBL. It thus appears that cSBL has therapeutic potential for the treatment of mesothelioma.

Inhibition of autophagy potentiates pemetrexed and simvastatin-induced apoptotic cell death in malignant mesothelioma and non-small cell lung cancer cells

Pemetrexed, a multitarget antifolate used to treat malignant mesothelioma and non-small cell lung cancer (NSCLC), has been shown to stimulate autophagy. In this study, we determined whether autophagy could be induced by pemetrexed and simvastatin cotreatment in malignant mesothelioma and NSCLC cells. Furthermore, we determined whether inhibition of autophagy drives apoptosis in malignant mesothelioma and NSCLC cells. Malignant mesothelioma MSTO-211H and A549 NSCLC cells were treated with pemetrexed and simvastatin alone and in combination to evaluate their effect on autophagy and apoptosis. Cotreatment with pemetrexed and simvastatin induced greater caspase-dependent apoptosis and autophagy than either drug alone in malignant mesothelioma and NSCLC cells. 3-Methyladenine (3-MA), ATG5 siRNA, bafilomycin A, and E64D/pepstatin A enhanced the apoptotic potential of pemetrexed and simvastatin, whereas rapamycin and LY294002 attenuated their induction of caspase-dependent apoptosis. Our data indicate that pemetrexed and simvastatin cotreatment augmented apoptosis and autophagy in malignant mesothelioma and NSCLC cells. Inhibition of pemetrexed and simvastatin-induced autophagy was shown to enhance apoptosis, suggesting that this could be a novel therapeutic strategy against malignant mesothelioma and NSCLC.

Pemetrexed induces G1 phase arrest and apoptosis through inhibiting Akt activation in human non small lung cancer cell line A549

Pemetrexed is an antifolate agent which has been used for treating malignant pleural mesothelioma and non small lung cancer in the clinic as a chemotherapeutic agent. In this study, pemetrexed inhibited cell growth and induced G1 phase arrest in the A549 cell line. To explore the molecular mechanisms of pemetrexed involved in cell growth, we used a two-dimensional polyacrylamide gel electrophoresis (2-DE) proteomics approach to analyze proteins changed in A549 cells treated with pemetrexed. As a result, twenty differentially expressed proteins were identified by ESI-Q-TOF MS/MS analysis in A549 cells incubated with pemetrexed compared with non-treated A549 cells. Three key proteins (GAPDH, HSPB1 and EIF4E) changed in pemetrexed treated A549 cells were validated by Western blotting. Accumulation of GAPDH and decrease of HSPB1 and EIF4E which induce apoptosis through inhibiting phosphorylation of Akt were noted. Expression of p-Akt in A549 cells treated with pemetrexed was reduced. Thus, pemetrexed induced apoptosis in A549 cells through inhibiting the Akt pathway.

Pemetrexed induces apoptosis in malignant mesothelioma and lung cancer cells through activation of reactive oxygen species and inhibition of sirtuin 1

Pemetrexed is a multitargeted antifolate used for the treatment of malignant mesothelioma and non-small cell lung cancer (NSCLC). However, the mechanism by which pemetrexed induces apoptosis remains unclear. In the present study, we investigated the involvement of reactive oxygen species (ROS) and sirtuin 1 (SIRT1) in pemetrexed-induced apoptosis in MSTO-211 malignant mesothelioma cells and A549 NSCLC cells. Pemetrexed enhanced caspase-dependent apoptosis, induced intracellular ROS generation, and downregulated SIRT1 in the MSTO-211 and A549 cells. Pemetrexed-induced apoptosis, which was prevented by pretreatment with N-acetyl-cysteine (NAC), was mediated by effects on the mitochondria, including mitochondrial membrane potential transition (MPT) and cytosolic release of cytochrome c, and also involved regulation of SIRT1 expression. Interference with SIRT1 expression using siRNA enhanced pemetrexed-induced apoptosis through mitochondrial dysfunction and ROS generation, whereas resveratrol, an activator of SIRT1, protected against pemetrexed-induced apoptosis. These results show that pemetrexed induces apoptosis in MSTO-211 mesothelioma cells and A549 NSCLC cells through mitochondrial dysfunction mediated by ROS accumulation and SIRT1 downregulation.

Enhanced apoptosis by pemetrexed and simvastatin in malignant mesothelioma and lung cancer cells by reactive oxygen species-dependent mitochondrial dysfunction and Bim induction

Pemetrexed is a multitarget antifolate currently used for the treatment of malignant mesothelioma and non-small cell lung cancer (NSCLC). Statins, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors used primarily for hyperlidpidemia, have been studied for their antiproliferative and pro-apoptotic effects. However, the effects of simvastatin on pemetrexed-induced apoptosis have not been investigated. In this study, we investigated whether combination treatment with pemetrexed and simvastatin potentiates the apoptotic activity above that is seen with either drug alone in malignant mesothelioma and NSCLC cells. We found that the combination of pemetrexed and simvastatin induced more extensive caspase-dependent apoptosis than either drug alone in malignant mesothelioma cells (MSTO-211) or NSCLC cells (A549). In addition, reactive oxygen species (ROS) generation in cells treated with both pemetrexed and simvastatin was markedly increased compared to cells treated with either pemetrexed or simvastatin alone. Combination treatment also increased the loss of mitochondrial membrane potential, increased cytosolic release of cytochrome c, and altered expression of inhibitor of apoptosis proteins (IAP) and B-cell lymphoma-2 (Bcl-2) families of apoptosis related proteins. On the other hand, pretreatment with N-acetylcysteine (NAC) prevented apoptosis and mitochondrial dysfunction by pemetrexed and simvastatin. In addition, Bim siRNA conferred protection against apoptosis induced by pemetrexed and simvastatin. These results suggest that combination of pemetrexed and simvastatin potentiates their apoptotic activity beyond that of either drug alone in malignant mesothelioma and lung cancer cells. This activity is mediated through ROS-dependent mitochondrial dysfunction and Bim induction.

Usp9x- and Noxa-mediated Mcl-1 downregulation contributes to pemetrexed-induced apoptosis in human non-small-cell lung cancer cells

Pemetrexed, a folate antimetabolite, combined with cisplatin is used as a first-line therapy for malignant pleural mesothelioma (MPM) and locally advanced or metastatic non-small-cell lung cancer (NSCLC). Pemetrexed arrests cell cycle by inhibiting three enzymes in purine and pyrimidine synthesis that are necessary for DNA synthesis. Pemetrexed also promotes apoptosis in target cells, but little is known about its mechanism in cancer cells. We have previously shown that pemetrexed can result in endoplasmic reticulum (ER) stress, and it can lead to downstream apoptosis. In this study, we further elucidate this mechanism. Our data show that pemetrexed increases Noxa expression through activating transcription factor 4 (ATF4) and activating transcription factor 3 (ATF3) upregulation. Furthermore, pemetrexed induces apoptosis by activating the Noxa-Usp9x-Mcl-1 pathway. Inhibition of Noxa by small interfering RNA (siRNA) promotes Usp9x (ubiquitin-specific peptidase 9, X-linked) expression. Moreover, downregulation of the deubiquitinase Usp9x by pemetrexed results in downstream reduction of myeloid cell leukemia 1 (Mcl-1) expression. Mechanistically, Noxa upregulation likely reduces the availability of Usp9x to Mcl-1, thereby promoting its ubiquitination and degradation, leading to the apoptosis of neoplastic cells. Thus, our findings demonstrate that Noxa-Usp9x-Mcl-1 axis may contribute to pemetrexed-induced apoptosis in human lung cancer cells.

The role of autophagy induced by pemetrexed in lung adenocarcinoma cells

Autophagy is known as an important regulatory mediator for cell survival or death and its important role in cancer. Pemetrexed (PTX) has been used in chemotherapy for lung cancer. However, the underlying molecular mechanisms have not been fully clarified. To investigate the role of autophagy induced by PTX in A549 cells, we performed MTT assay, acridine orange staining, western blotting, Annexin V/PI by using the 3-MA autophagy inhibitor. PTX induced autophagy after 48 h treatment in A549 cells. Furthermore, PTX showed acidic vesicular organelles (AVOs) and expressed LC3-II in A549 cells. The induction of autophagy by PTX was inhibited by 3-MA which was confirmed by reduced AVOs. When the autophagy was inhibited, Annexin V was increased. In addition, PARP cleavage was increased as shown by western blotting. Taken together, PTX induced autophagy in A549 cells and these cellular events possibly cause the apoptotic and/or necrotic cell death of A549 cells.

Molecular mechanism implicated in Pemetrexed-induced apoptosis in human melanoma cells

Background

Metastatic melanoma is a lethal skin cancer and its incidence is rising every year. It represents a challenge for oncologist, as the current treatment options are non-curative in the majority of cases; therefore, the effort to find and/or develop novel compounds is mandatory. Pemetrexed (Alimta®, MTA) is a multitarget antifolate that inhibits folate-dependent enzymes: thymidylate synthase, dihydrofolate reductase and glycinamide ribonucleotide formyltransferase, required for de novo synthesis of nucleotides for DNA replication. It is currently used in the treatment of mesothelioma and non-small cell lung cancer (NSCLC), and has shown clinical activity in other tumors such as breast, colorectal, bladder, cervical, gastric and pancreatic cancer. However, its effect in human melanoma has not been studied yet.

Results

In the current work we studied the effect of MTA on four human melanoma cell lines A375, Hs294T, HT144 and MeWo and in two NSCLC cell lines H1299 and Calu-3. We have found that MTA induces DNA damage, S-phase cell cycle arrest, and caspase- dependent and –independent apoptosis. We show that an increment of the intracellular reactive oxygen species (ROS) and p53 is required for MTA-induced cytotoxicity by utilizing N-Acetyl-L-Cysteine (NAC) to blockage of ROS and p53-defective H1299 NSCLC cell line. Pretreatment of melanoma cells with NAC significantly decreased the DNA damage, p53 up-regulation and cytotoxic effect of MTA. MTA was able to induce p53 expression leading to up-regulation of p53-dependent genes Mcl-1 and PIDD, followed by a postranscriptional regulation of Mcl-1 improving apoptosis.

Conclusions

We found that MTA induced DNA damage and mitochondrial-mediated apoptosis in human melanoma cells in vitro and that the associated apoptosis was both caspase-dependent and –independent and p53-mediated. Our data suggest that MTA may be of therapeutic relevance for the future treatment of human malignant melanoma.

Five cases report of solid tumor synchronously with hematologic malignancy

The reported incidence of synchronous multiple primary cancer (SMPC) is rare, and it is even less common to observe synchronous solid tumor with a hematological malignancy. We report five cases of solid tumor presented synchronously with hematological malignancy, all observed within a 2 year period at the oncology department of a university hospital in Shanghai, China. These individual cases included lung adenocarcinoma with chronic myelogenous leukemia, colon cancer with solitary plasmocytoma, gastric adenocarcinoma with diffuse large B cell non-Hodgkin's lymphoma, lung adenocarcinoma with multiple myeloma, and colon cancer with diffuse large B cell non-Hodgkin's lymphoma. It is challenging to therapeutically control the biological behavior of concurrent multiple primary tumors, and there is no standard treatment for such rare conditions. In this paper we discuss these five cases of SMPC and their treatments.

Pemetrexed induces both intrinsic and extrinsic apoptosis through ataxia telangiectasia mutated/p53-dependent and -independent signaling pathways

Pemetrexed, a new-generation antifolate, has demonstrated promising single-agent activity in front- and second-line treatments of non-small cell lung cancer. However, the molecular mechanism of pemetrexed-mediated antitumor activity remains unclear. The current study shows that pemetrexed induced DNA damage and caspase-2, -3, -8, and -9 activation in A549 cells and that treatment with caspase inhibitors significantly abolished cell death, suggesting a caspase-dependent apoptotic mechanism. The molecular events of pemetrexed-mediated apoptosis was associated with the activation of ataxia telangiectasia mutated (ATM)/p53-dependent and -independent signaling pathways, which promoted intrinsic and extrinsic apoptosis by upregulating Bax, PUMA, Fas, DR4, and DR5 and activating the caspase signaling cascade. Supplementation with dTTP allowed normal S-phase progression and rescued apoptotic death in response to pemetrexed. Overall, our findings reveal that the decrease of thymidylate synthase and the increase of Bax, PUMA, Fas, DR4, and DR5 genes may serve as biomarkers for predicting responsiveness to pemetrexed.

Chemotherapeutic-induced apoptosis: a phenotype for pharmacogenomics studies

AIM

To determine whether cellular apoptosis is a suitable phenotypic trait for pharmacogenomics studies by evaluating caspase 3/7-mediated activity in lymphoblastoid cell lines after treatment with six chemotherapeutic agents: 5'-deoxyfluorouridine, pemetrexed, cytarabine, paclitaxel, carboplatin, and cisplatin.

MATERIALS AND METHODS

Using monozygotic twin pair and sibling pair lymphoblastoid cell lines, we identified conditions for measurement of caspase 3/7 activity in lymphoblastoid cell lines. Genome-wide association studies were performed with over 2 million single nucleotide polymorphisms (SNPs) and cisplatin-induced apoptosis in HapMap CEU cell lines (n=77).

RESULTS

Although treatment with 5'-deoxyfluorouridine and pemetrexed for up to 24 h resulted in low levels of apoptosis or interindividual variation in caspase-dependent cell death; paclitaxel, cisplatin, carboplatin, and cytarabine treatment for 24 h resulted in 9.4-fold, 9.1-fold, 7.0-fold, and 6.0-fold increases in apoptosis relative to control, respectively. There was a weak correlation between caspase activity and cytotoxicity (r(2)=0.03-0.29) demonstrating that cytotoxicity and apoptosis are two distinct phenotypes that may produce independent genetic associations. Estimated heritability (h(2)) for apoptosis was 0.57 and 0.29 for cytarabine (5 and 40 μmol/l, respectively), 0.22 for paclitaxel (12.5 nmol/l), and 0.34 for cisplatin (5 μmol/l). In the genome-wide association study using the HapMap CEU panel, we identified a significant enrichment of cisplatin-induced cytotoxicity SNPs within the significant cisplatin-induced apoptosis SNPs and an enrichment of expression quantitative trait loci (eQTL). Among these eQTLs, we identified several eQTLs with known function related to apoptosis and/or cytotoxicity.

CONCLUSION

Our study identifies apoptosis as a phenotype for pharmacogenomic studies in lymphoblastoid cell lines after treatment with paclitaxel, cisplatin, carboplatin, and cytarabine that may have utility for discovering biomarkers to predict response to certain chemotherapeutics.

Death receptor 5 and cellular FLICE-inhibitory protein regulate pemetrexed-induced apoptosis in human lung cancer cells

Pemetrexed is a clinically available anti-folate therapeutic agent used in combination with cisplatin for the management of patients with malignant pleural mesothelioma and advanced non-small cell lung cancer. Pemetrexed inhibits three enzymes in purine and pyrimidine synthesis necessary for precursor DNA nucleotides which in turn disrupts growth and survival of normal and cancer cells. The mechanism by which pemetrexed induces apoptosis remains largely uncharacterised. In the current study, we examined the downstream effect of pemetrexed in inducing apoptosis in lung cancer cells. We showed that pemetrexed induced apoptosis via up-regulation of Death Receptor 5 (DR5), an important death receptor for tumour necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL). In addition, we discovered a synergistic effect of combination pemetrexed and recombinant TRAIL in inducing apoptosis. Modulating DR5 induction by small interfering RNA abrogated the ability of pemetrexed to induce apoptosis. In addition, silencing of C/EBP homologous protein (CHOP) expression reduced DR5 expression, demonstrating that the transcriptional factor CHOP has a pivotal role on DR5 up-regulation following pemetrexed treatment. In addition, enforced expression of cellular FLICE-inhibitory protein (c-FLIP), a known inhibitor of caspase 8, protected neoplastic cells from apoptosis despite pemetrexed and/or TRAIL therapy. Thus, our findings demonstrate the efficacy and mechanistic underpinnings of pemetrexed-induced apoptosis, and they suggest pemetrexed may have clinical utility when used in combination with TRAIL for the management of patients with lung cancer.

Valproate, in combination with pemetrexed and cisplatin, provides additional efficacy to the treatment of malignant mesothelioma

PURPOSE

Present chemotherapeutic regimens are marginally efficient in tumor cells being particularly resistant to radiotherapy and/or chemotherapy. We hypothesized that unresponsiveness of tumors to conventional therapeutic agents might be due to inappropriate gene expression resulting from epigenetic modifications and leading to transcriptional silencing. The goal of this study was to evaluate the anticancer effect of a histone deacetylase inhibitor, valproate, on mesothelioma cells in combination with pemetrexed and cisplatin, the usual first-line regimen of chemotherapy for this tumor.

EXPERIMENTAL DESIGN AND RESULTS

We show that valproate augments apoptosis induced by pemetrexed and cisplatin in mesothelioma cell lines and in tumor cells from patient's biopsies. Onset of apoptosis involves both extrinsic and intrinsic pathways requiring enzymatic activities of caspases 8 and 9, respectively. Valproate but not suberoylanilide hydroxamic acid efficiently stimulates the production of reactive oxygen species. The free radical scavenger N-acetylcysteine inhibits apoptosis, indicating that reactive oxygen species are major mediators of valproate activity. As expected, valproate alone or combined with pemetrexed and cisplatin triggers hyperacetylation of histone H3. Bid protein processing in truncated t-Bid and cytochrome c release from mitochondria are significantly increased in the presence of valproate, providing a mechanistic rationale for improvement of the proapoptotic efficacy of cisplatin and pemetrexed. Finally, valproate when combined with pemetrexed and cisplatin prevents tumor growth in mouse models of epithelioid mesothelioma.

CONCLUSIONS

These observations support the potential additional efficacy of valproate in combination with pemetrexed and cisplatin for treatment of malignant mesothelioma.