Cisplatin resistant glioblastoma cells may have increased concentration of urokinase plasminogen activator and plasminogen activator inhibitor type 1

PLAU promotes growth and attenuates cisplatin chemosensitivity in ARID1A-depleted non-small cell lung cancer through interaction with TM4SF1

Loss of ARID1A, a subunit of the SWI/SNF chromatin remodeling complex, contributes to malignant progression in multiple cancers including non-small cell lung cancer (NSCLC). In the search for key genes mediating the aggressive phenotype caused by ARID1A loss, we analyzed 3 Gene Expression Omnibus (GEO) datasets that contain RNA sequencing data from ARID1A-depleted cancer cells. PLAU was identified as a common gene that was induced in different cancer cells upon ARID1A depletion. Overexpression of PLAU positively modulated NSCLC cell growth, colony formation, cisplatin resistance, and survival under serum deprivation. Moreover, enforced expression of PLAU enhanced tumorigenesis of NSCLC cells in nude mice. Mechanistically, PLAU interacted with TM4SF1 to promote the activation of Akt signaling. TM4SF1-overexpressing NSCLC cells resembled those with PLAU overepxression. Knockdown of TM4SF1 inhibited the growth and survival and increased cisplatin sensitivity in NSCLC cells. The interaction between PLAU and TM4SF1 led to the activation of Akt signaling that endowed ARID1A-depleted NSCLC cells with aggressive properties. In addition, treatment with anti-TM4SF1 neutralizing antibody reduced the growth, cisplatin resistance, and tumorigenesis of ARID1A-depleted NSCLC cells. Taken together, PLAU serves as a target gene of ARID1A and promotes NSCLC growth, survival, and cisplatin resistance by stabilizing TM4SF1. Targeting TM4SF1 may be a promising therapeutic strategy for ARID1A-mutated NSCLC.

Gasotransmitter CO Attenuates Bleomycin-Induced Fibroblast Senescence via Induction of Stress Granule Formation

Cellular senescence is recognized as a phenomenon wherein a proliferative cell undergoes a permanent growth arrest. The accumulation of senescent cells over time can become harmful and result in diseases and physiological decline. Plasminogen activator inhibitor (PAI-1) is considered as a critical marker and mediator of cellular senescence. The formation of stress granules (SGs) could prevent senescence through the sequestration of PAI-1, and we previously suggested that exogenous carbon monoxide (CO) could induce SG assembly via integrated stress response (ISR). Although CO is known to possess anti-inflammatory, antioxidative, and antiapoptotic properties, whether it exerts antisenescent effect is still not well defined. Here, to address whether CO-induced SGs could protect against cellular senescence, we first treated lung fibroblasts with bleomycin (BLM) to establish DNA damage-induced cellular senescence, and observed a significant increase of several hallmarks of senescence through SA-β-gal staining, immunofluorescence, qRT-PCR, and Western blot assay. However, pre- and posttreatment of CO could remarkably attenuate these senescent phenotypes. According to our immunofluorescence results, CO-induced SGs could inhibit BLM-induced cellular senescence via sequestration of PAI-1, while it was abolished after the cotreatment of ISR inhibitor (ISRIB) due to the inhibition of SG assembly. Overall, our results proposed a novel role of CO in suppressing bleomycin-induced lung fibroblast senescence through the assembly of SGs.

Investigating Glioblastoma Response to Hypoxia

Glioblastoma (GB) is the most common and deadly type of primary malignant brain tumor with an average patient survival of only 15–17 months. GBs typically have hypoxic regions associated with aggressiveness and chemoresistance. Using patient derived GB cells, we characterized how GB responds to hypoxia. We noted a hypoxia-dependent glycolytic switch characterized by the up-regulation of HK2, PFKFB3, PFKFB4, LDHA, PDK1, SLC2A1/GLUT-1, CA9/CAIX, and SLC16A3/MCT-4. Moreover, many proangiogenic genes and proteins, including VEGFA, VEGFC, VEGFD, PGF/PlGF, ADM, ANGPTL4, and SERPINE1/PAI-1 were up-regulated during hypoxia. We detected the hypoxic induction of invasion proteins, including the plasminogen receptor, S100A10, and the urokinase plasminogen activator receptor, uPAR. Furthermore, we observed a hypoxia-dependent up-regulation of the autophagy genes, BNIP-3 and DDIT4 and of the multi-functional protein, NDRG1 associated with GB chemoresistance; and down-regulation of EGR1 and TFRC (Graphical abstract). Analysis of GB patient cohorts’ revealed differential expression of these genes in patient samples (except SLC16A3) compared to non-neoplastic brain tissue. High expression of SLC2A1, LDHA, PDK1, PFKFB4, HK2, VEGFA, SERPINE1, TFRC, and ADM was associated with significantly lower overall survival. Together these data provide important information regarding GB response to hypoxia which could support the development of more effective treatments for GB patients.

Long noncoding RNA MALAT1 knockdown reverses chemoresistance to temozolomide via promoting microRNA-101 in glioblastoma

Glioblastoma (GBM) is the most common and lethal tumor of the central nervous system with highly infiltrative and resistant to chemotherapy. Temozolomide (TMZ) is widely used as the first-line treatment for the therapy of GBM. However, a considerable percentage inherent or acquired resistance in GBM accounts for many treatment failures of the TMZ chemotherapy. Therefore, a deeper understanding of the molecular characteristics underlying TMZ resistance and the identification of novel therapeutic target is urgent. Here, we show that MALAT1 was significantly upregulated in TMZ-resistant GBM cells. On the other hand, MALAT1 knockdown reduces TMZ resistance of GBM cells both in vitro and in vivo by inhibiting cell proliferation and promoting apoptosis. We also show that miR-101 overexpression reduced TMZ resistance of GBM cells and played an antagonistic role compared with MALAT1. Importantly, we demonstrate that MALAT1 promoted the chemoresistance through suppressing miR-101 signaling pathway via directly binding it in GBM cells. In conclusion, our study indicates that knockdown of MALAT1 reverses chemoresistance to TMZ via promoting miR-101 regulatory network in GBM and thus offers a novel prognostic marker and potential target for GBM TMZ-based chemotherapy.

A urokinase receptor-Bim signaling axis emerges during EGFR inhibitor resistance in mutant EGFR glioblastoma

EGFR is the most common genetically altered oncogene in glioblastoma (GBM), but small-molecule EGFR tyrosine kinase inhibitors (TKI) have failed to yield durable clinical benefit. Here, we show that in two novel model systems of acquired resistance to EGFR TKIs, elevated expression of urokinase plasminogen activator (uPA) drives signaling through the MAPK pathway, which results in suppression of the proapoptotic BCL2-family member protein BIM (BCL2L11). In patient-derived GBM cells and genetic GBM models, uPA is shown to suppress BIM levels through ERK1/2 phosphorylation, which can be reversed by siRNA-mediated knockdown of uPA. TKI-resistant GBMs are resensitized to EGFR TKIs by pharmacologic inhibition of MEK or a BH3 mimetic drug to replace BIM function. A link between the uPA-uPAR-ERK1/2 pathway and BIM has not been previously demonstrated in GBM, and involvement of this signaling axis in resistance provides rationale for a new strategy to target EGFR TKI-resistant GBM.

PMA and doxorubicin decrease viability, MTT activity and expression of CD10 marker on NALM-1 leukemic cells

PMA (10, 20 ng/ml) and doxorubicin (5-20 ng/ml) decreased the viability and MTT-activity of NALM-1 pre-B leukemic cells (3 days' treatment). Further, CD10 was downregulated, suggesting that PMA and doxorubicin induced differentiation of NALM-1 cells. However, PMA did not alter expression of B cell markers CD20 and of mIgM. In contrast to PMA, another differentiation agent ATRA did not alter CD10 expression on NALM-1 cells but affected viability after 6 days (5, 10 ng/ml). The data in this study are the first evidence that PMA and doxorubicin inhibited viability and MTT activity and induced partial differentiation, by decreasing CD10 on NALM-1 cells.

Lithium increases expression of p21WAF/Cip1 and survivin in human glioblastoma cells

Lithium is the most widely prescribed mood stabilizer, but the precise molecular mechanisms underlying its therapeutic function are not yet fully elucidated. Recent preclinical and clinical evidence indicates its neuroprotective and neurotrophic effects. As a tight coupling of function and metabolism in the central nervous system between glial cells and neurons has recently been detected, lithium's effect on glial cells may participate also in the total beneficial effects of this drug. The aim of the present study was to analyze molecular mechanisms induced in human glioblastoma A1235 cells by the treatment with lithium, especially its influence on the expression of apoptosis-related genes. Lower levels of lithium (0.5 mmol/L and 2 mmol/L) did not cause any cytotoxicity or changes in the cell cycle phase distribution following 72 h incubation. However, a higher dose (20 mmol/L) was cytostatic for glioblastoma cells, and caused accumulation of cells in G(2)/M phase of the cell cycle. The treatment with lithium did not alter the levels of Bcl-2 or procaspase-3 and did not cleave PARP, but increased the levels of p21(WAF/Cip1) and survivin. Thus, increased expression of p21(WAF/Cip1) (a protein with antiapoptotic function), and survivin (a protein that supports the growth of cells by suppression of apoptosis and promotion of cell proliferation) may be the early events in the long-term cell response to lithium that are involved in the beneficial effects of this drug.

Enhanced therapeutic efficacy of G207 for the treatment of glioma through Musashi1 promoter retargeting of gamma34.5-mediated virulence

G207 is a conditionally replicating derivative of herpes simplex virus type1 (HSV-1) engineered with deletions of both ICP34.5 loci and a lacZ insertion disabling the ICP6 gene. G207 exhibits an efficient oncolytic activity in vitro and in vivo, yet minimal toxicity in normal tissue, and is now in clinical trial for malignant glioma. According to the results of clinical trials, however, although G207 was proved to be safe, the efficacy was not so impressive. Deletion of the ICP34.5 gene coding for virulence made G207 extremely safe, but it markedly reduced the cytotoxicity mediated by HSV-1. To enhance the therapeutic efficacy of G207 without diminishing its safety, we used a defective vector containing Musashi1 promoter/ICP34.5, with G207 as helper virus. P/musashi1 was functional selectively in human glioma cell lines (U87MG, U251, T98G) in this study and dvM345 showed a much higher therapeutic efficacy both in culture and in the in vivo glioma model, than G207 alone, without diminishing its favorable toxicity profile. These results suggest that transcriptional regulation of ICP34.5 by P/musashi1 can be used to target HSV-1 virulence toward gliomas while maintaining the desirable neuroattenuated phenotype.

Methyl 2-(2-chloroethylaminocarbonyl)diazenecarboxylate SB-166 inhibits the growth of different tumour cell lines, including drug-resistant sublines

Recently we synthesized new drugs, diazenecarboxamides (shortly diazenes), that were cytotoxic for several tumour cell lines. Because the solubility and biological activity of these drugs was relatively low, new compounds have been synthesized. In the present study we examined the cytotoxic effect of nine compounds: an imidazolidin-2-one (SB-282: methyl 5-benzoyl-3-(2-chloroethyl)-2-oxo-4-phenyl-2,3-dihydro-1H-imidazol-1-ylcarbamate), two diazenecarboxamides (UP-140: N-phenyl-2-(2-quinolinyl)diazenecarboxamide; JK-1090: N-(4-iodophenyl)-2-(2-pyridinyl)diazenecarboxamide), two aminocarbonyl substituted diazenecarboxylates (SB-178: methyl 2-[(cyclohexylamino)carbonyl]diazenecarboxylate; SB-166: methyl 2-[[(2-chloroethyl)amino]carbonyl]diazenecarboxylate) and four diazenedicarboxamides (SB-410: N(1)-(2-chloroethyl)-N(2)-(2-pyridinylmethyl)-1,2-diazenedicarboxamide; SB-472: N(1)-(2-chloroethyl)-N(2)-(4-isopropylphenyl)-1,2-diazenedicarboxamide; SB-503: N(1)-(4-sec-butylphenyl)-N(2)-(2-chloroethyl)-1,2-diazenedicarboxamide; SB-474: N(1)-(4-tert-butylphenyl)-N(2)-(2-chloroethyl)-1,2-diazenedicarboxamide). Using a modified colorimetric MTT assay, their cytotoxicity was determined on eight human cell lines: laryngeal carcinoma parental and two drug-resistant cell lines, glioblastoma parental and drug-resistant cell lines, cervical carcinoma parental and drug-resistant cell lines and breast adenocarcinoma cells. Results show that diazene SB-166 was very effective, reducing significantly the cell survival of all eight examined cell lines, including four drug-resistant cell lines. Compound SB-410 was cytotoxic for all examined cell lines, but mostly only in the highest concentration. Other compounds were not significantly cytotoxic to any of the treated cell lines. Our results, especially those obtained on drug-resistant cells, encourage further research on compound SB-166 as a potential anticancer drug.

Highly efficient and tumor-restricted gene transfer to malignant gliomas by replication-competent retroviral vectors

The first large randomized phase III trial in gene therapy demonstrated no improvement in the survival of patients injected with packaging cells that produced conventional replication-defective retroviral vectors carrying the herpes simplex virus thymidine kinase gene, a disappointing result that was attributed to extremely poor levels of transduction efficiency. To circumvent this problem, we have developed a modified replication-competent retrovirus (RCR) that is capable of transducing human glioma cell lines A-172, U-87, T-98G, U-373, and U-138 and rat glioma cell lines C6 and 9L, over multiple infection cycles in vitro, resulting in a tremendous enhancement in transduction efficiency over conventional replication-defective retroviral vectors at the same dose. Whereas the transduction efficiency of conventional retroviral vectors injected into preestablished subcutaneous U-87 tumors at a dose of 1.0 x 10(5) transducing units (TU) was only 0.2% at 6 weeks postinjection, the same dose of RCR vector resulted in up to 97.2% transduction. When RCR vectors at a dose of 1.0 x 10(4) TU were injected into preestablished intracranial U-87 tumors, transduction efficiency at 2 and 3 weeks was 74 and 98.1%, respectively. Notably, however, intracranial injection of RCR vectors did not result in detectable infection of normal brain cells. Furthermore, using a sensitive polymerase chain reaction assay, no detectable RCR signal could be observed in any extracerebral tissues, including lung, liver, kidney, upper gastrointestinal tract (esophagus and stomach), lower gastrointestinal tract (colon and small intestine), skin, spleen, and bone marrow. Treatment of U-87 intracranial gliomas with RCR vectors carrying the yeast cytosine deaminase suicide gene followed by 5-fluorocytosine prodrug administration resulted in 100% survival over a 60-day follow-up period, compared with 0% survival of control groups receiving vector alone or prodrug alone. Our results demonstrate that RCR vectors can achieve therapeutically significant levels of transduction in malignant human gliomas, and that RCR vector spread after intratumoral injection is restricted to the tumor itself.

Diazenecarboxamide UP-91, a potential anticancer agent, acts by reducing cellular glutathione content

Glutathione (GSH) is a ubiquitous non-protein thiol essential for cellular homeostasis and protection. Diazenecarboxamides (diazenes) are new compounds that could, according to their biochemical properties, lower the intracellular GSH content, thus inhibiting the growth of tumour cells. In the present study we examined four such compounds: JK-914, JK-918, JK-1013 and UP-91. Their cytotoxic effect on the growth of eight human tumour cell lines (glioblastoma, cervical and laryngeal carcinoma cells, mammary carcinoma cells and four drug-resistant sublines) was determined using a modified colorimetric MTT assay. The rate of reaction of thiophenol (as a model thiol) with diazenes leading to diphenyl disulfide was established by chromatography (TLC). Reactivity of diazenes with GSH under quasi-physiological conditions was determined by NMR spectroscopy. Intracellular GSH content was examined spectrophotometrically by the procedure developed by Tietze (1969). Diazene UP-91 reduced significantly the cell survival of all eight examined cell lines, including four drug-resistant cell lines. Other diazenes did not influence the survival of tumour cells. Reaction time for quantitative conversion of thiophenol to diphenyl disulfide was shortest for diazene UP-91, which is highly consistent with high reactivity of the same diazene with GSH, observed under quasi-physiological conditions. UP-91 reduced intracellular GSH level, while other diazenes had no effect on it. Thus, diazenecarboxamides UP-91 is a potential anticancer agent that may inhibit the growth of tumour cells due to reduction in glutathione level.

Comparisons of tumor suppressor p53, p21, and p16 gene therapy effects on glioblastoma tumorigenicity in situ

The mutation and/or deletion of tumor suppressor genes have been postulated to play a major role in the genesis and the progression of gliomas. In this study, the functional expression and efficacy in tumor suppression of 3 tumor suppressor genes (p53, p21, and p16) were tested and compared in a rat GBM cell line (RT-2) after retrovirus mediated gene delivery in vitro and in vivo. Significant reductions in tumor cell growth rate were found in p16 and p21 infected cells (60 +/- 12% vs 66 +/- 15%) compared to p53 (35 +/- 9%). In vitro colony formation assay also showed significant reductions after p16 and p21 gene delivery (98 +/- 5% vs 91 +/- 10%) compared to p53 (50 +/- 18%). In addition, the tumor suppression efficacy were investigated and compared in vivo. Retroviral mediated p16 and p21 gene deliveries in glioblastomas resulted in more than 90% reductions in tumor growth (92 +/- 26% vs 90 +/- 22%) compared to p53 (62 +/- 18%). Tumor suppressor gene insertions in situ further prolonged animal survival. Overall p16 and p21 genes showed more powerful tumor suppressor effects than p53. The results were not surprising, as p16 and p21 are more downstream in the cell cycle regulatory pathway compared to p53. Moreover, the mechanism involved in each of their suppressor effects is different. This study demonstrates the feasibility of using tumor suppressor genes in regulating the growth of glioma in vitro and in situ.