Abstract P06-01: A phase I, first-in-human clinical trial of the GDF-15 neutralizing antibody CTL-002 in subjects with advanced stage solid tumors (Acronym: GDFATHER)

Background: Growth and differentiation factor 15 (GDF-15) is a TGF-β superfamily member physiologically expressed mainly in placenta and linked to feto-maternal tolerance. Under pathophysiologic conditions, prevention of excessive immune cell infiltration during tissue damage and cachexia induction have been ascribed to GDF-15. A recent study [Haake et al. AACR2020; Abstract #5597] elucidated a mechanism by which GDF-15 inhibits LFA-1 activation on CD8+ T cells, thus interfering with effector T cell recruitment to tissues. Importantly, several cancer entities secrete high levels of GDF-15, correlating with poor prognosis and reduced overall survival [reviewed in Front Immunol 2020 May 19;11:951]. To block this effect the GDF-15 neutralizing antibody CTL-002 was generated. In preclinical models CTL-002 demonstrated potent effector T cell shifting into tumor tissue by neutralizing GDF-15 and enhancing response to checkpoint inhibitor therapy. Methods: This is a phase 1, first-in-human (FIH), two-part, open-label clinical trial of intravenous (IV) administration of CTL-002 given as monotherapy and in combination with an anti-PD-1 antibody in subjects with advanced-stage, relapsed/refractory solid tumors who relapsed on or were refractory to a prior anti-PD-1/PD-L1 therapy. Eligible subjects have exhausted all available approved standard treatments, including prior anti-PD1/-PD-L1 treatment, and present with a biopsy-accessible tumor for serial biopsy taking. The trial is termed GDFATHER, for “GDF-15 Antibody-mediaTed Effector cell Relocation”. Main endpoints are safety of CTL-002 monotherapy and CTL-002 combination with an anti-PD-1 antibody, pharmacokinetics, pharmacodynamics (e.g., degree of GDF-15 neutralization achieved and change in immune-cell number and composition in the tumor tissue) as well as preliminary clinical efficacy (tumor mass reduction; anticachexia effect). In part A of the trial (dose escalation) up to 24 subjects will receive escalating doses of CTL-002 IV (0.3 – 20 mg/kg) in a „mono-followed-by-combination“-design with CTL-002 given as monotherapy and followed by combination with an anti-PD-1 checkpoint inhibitor. In part B (expansion) up to 5 cohorts with up to 25 subjects per cohort with defined tumor entities expected to be GDF-15 dependent will be treated to determine the recommended phase 2 dose (RP2D) and further evaluate safety and preliminary efficacy of CTL-002 monotherapy and the combination. The study was initiated in December 2020 and enrolled the first patient on Dec 09, 2020. Cohort 4 is ongoing at time of submission (07/2021) and so far no DLT has occurred. Updated safety, biomarker and response assessments will be reported. The ClinicalTrials.gov Identifier is NCT04725474.

Citation Format: Ignacio Melero, Emiliano Calvo, Maria-Elisabeth Goebeler, Elena Garralda, Reinhard Dummer, María Rodríguez-Ruiz, María De Miguel, Cyrus Sayehli, Guzman Alonso Casal, Egle Ramelyte, Martin Schuler, Tanja Gromke, Miguel Sanmamed, Irene Moreno, Ralf Bargou, Maria Lostes, Julia-Tatjana Maul, Heike Richly, Petra Fettes, Kathrin Klar, Christine Schuberth-Wagner, Markus Haake, Joerg Wischhusen, Eugen Leo. A phase I, first-in-human clinical trial of the GDF-15 neutralizing antibody CTL-002 in subjects with advanced stage solid tumors (Acronym: GDFATHER) [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P06-01.

A phase I, first-in-human clinical trial of the GDF-15 neutralizing antibody CTL-002 in subjects with advanced-stage solid tumors (ACRONYM: GDFATHER)

TPS2658

Background: Growth and differentiation factor 15 (GDF-15) is a TGF-β superfamily member physiologically expressed mainly in placenta and linked to feto-maternal tolerance. Under pathophysiologic conditions, prevention of excessive immune cell infiltration during tissue damage and cachexia induction have been ascribed to GDF-15. A recent study [Haake et al. AACR2020; Abstract #5597] elucidated a mechanism by which GDF-15 inhibits LFA-1 activation on CD8+ T cells, thus interfering with effector T cell recruitment to tissues. Importantly, several cancer entities secrete high levels of GDF-15, correlating with poor prognosis and reduced overall survival [reviewed in Front Immunol 2020 May 19;11:951]. To block this effect the GDF-15 neutralizing antibody CTL-002 was generated. In preclinical models CTL-002 demonstrated potent effector T cell shifting into tumor tissue by neutralizing GDF-15. Methods: This is a phase 1, first-in-human (FIH), two-part, open-label clinical trial of intravenous (IV) administration of CTL-002 given as monotherapy and in combination with an anti-PD-1 antibody in subjects with advanced-stage, relapsed/refractory solid tumors who relapsed post or were refractory to a prior anti-PD-1/PD-L1 therapy. Eligible subjects have exhausted all available approved standard treatments. Further key eligibility criteria include having received at least one prior anti-PD1/-PD-L1 treatment and having relapsed on or after it or having been refractory to it, and presenting with a biopsy-accessible tumor for serial biopsy taking. The trial is termed GDFATHER, for “GDF-15 Antibody-mediaTed Effector cell Relocation”. Main endpoints are safety of CTL-002 monotherapy and CTL-002 combination with an anti-PD-1 antibody, pharmacokinetics, pharmacodynamics (e.g. degree of GDF-15 neutralization achieved and change in immune-cell number and composition in the tumor tissue) as well as preliminary clinical efficacy (tumor mass reduction; anticachexia effect) In part A of the trial (dose escalation) up to 24 subjects will receive escalating doses of CTL-002 IV (0.3 – 20 mg/kg) in a „mono-followed-by-combination“-design with CTL-002 given as monotherapy and followed by combination with an anti-PD-1 checkpoint inhibitor. In part B (expansion) up to 5 cohorts with up to 25 subjects per cohort with defined tumor entities expected to be GDF-15 dependent will be treated to determine the recommended phase 2 dose (RP2D) and further evaluate safety and preliminary efficacy of CTL-002 monotherapy and the combination. The study was initiated in December 2020 and enrolled the first patient on Dec 09, 2020. Cohort 1 has been completed without DLT and enrollment for cohort 2 began in February 2021. Clinical trial information: NCT04725474.

Tumor-derived GDF-15 to suppress t-lymphocyte recruitment to the tumor microenvironment resulting in resistance to ANTI-PD-1 treatment

e14532

Background: Growth and differentiation factor 15 (GDF-15) is a divergent member of the TGF-β superfamily with low to absent expression in healthy tissue. GDF-15 has been linked to feto-maternal immune tolerance, to prevention of excessive immune cell infiltration during tissue damage, and to anorexia. Various major tumor types secrete high levels of GDF-15. In cancer patients, elevated GDF-15 serum levels correlate with poor prognosis and reduced overall survival (OS). Methods: Impact of a proprietary GDF-15 neutralizing antibody (CTL-002) regarding T cell trafficking was analyzed by whole blood adhesion assays, a HV18-MK melanoma-bearing humanized mouse model and a GDF-15-transgenic MC38 model. Additionally, patient GDF-15 serum levels were correlated with clinical response and overall survival in oropharyngeal squamous cell carcinoma (OPSCC) and melanoma brain metastases. Results: In whole blood cell adhesion assays GDF-15 impairs adhesion of T and NK cells to activated endothelial cells. Neutralization of GDF-15 by CTL-002 rescued T cell adhesion. In HV18-MK-bearing humanized mice CTL-002 induced a strong increase in TIL numbers. Subset analysis revealed an overproportional enrichment of T cells, in particular CD8+ T cells. As immune cell exclusion is detrimental for checkpoint inhibitor (CPI) therapy, a GDF-15-transgenic MC38 model was tested for anti-PD-1 therapy efficacy. In GDF-15 overexpressing MC38 tumors response to anti PD-1 therapy was reduced by 90% compared to wtMC38 tumors. Combining aPD-1 with CTL-002 resulted in 50% of the mice rejecting their GDF-15 overexpressing tumors. Clinically, inverse correlations of GDF-15 levels with CD8+ T cell infiltration were shown for HPV+ OPSCC and for melanoma brain metastases. GDF-15 serum levels were significantly higher in HPV- than in HPV+ OPSCC patient (p < 0.0001). Low GDF-15 levels corresponded to longer OS in both HPV- and HPV+ OPSCC. In two independent melanoma patient cohorts treated with nivolumab or pembrolizumab low baseline serum GDF-15 levels were predictive for clinical response to anti-PD1 treatment and superior OS. Bivariate analysis including LDH indicates that GDF-15 independently predicts poor survival in aPD-1 treated melanoma patients. Conclusions: Taken together our in vitro and in vivo data show that elevated GDF-15 levels block T-cell infiltration into tumor tissues. Neutralizing GDF-15 with CTL-002 restores the ability of T cells to extravasate blood vessels and enter tumor tissue both in vitro and in vivo. In melanoma, patients with higher GDF-15 levels have significantly shorter survival and are less likely to respond to anti-PD1 therapy. GDF-15 may thus serve as a new predictive biomarker for anti-PD1 response, but most importantly also represents a novel target for cancer immunotherapy to improve tumor immune cell infiltration and response to anti-PD1 therapy.

CD74 regulates complexity of tumor cell HLA class II peptidome in brain metastasis and is a positive prognostic marker for patient survival

Despite multidisciplinary local and systemic therapeutic approaches, the prognosis for most patients with brain metastases is still dismal. The role of adaptive and innate anti-tumor response including the Human Leukocyte Antigen (HLA) machinery of antigen presentation is still unclear. We present data on the HLA class II-chaperone molecule CD74 in brain metastases and its impact on the HLA peptidome complexity.We analyzed CD74 and HLA class II expression on tumor cells in a subset of 236 human brain metastases, primary tumors and peripheral metastases of different entities in association with clinical data including overall survival. Additionally, we assessed whole DNA methylome profiles including CD74 promoter methylation and differential methylation in 21 brain metastases. We analyzed the effects of a siRNA mediated CD74 knockdown on HLA-expression and HLA peptidome composition in a brain metastatic melanoma cell line.We observed that CD74 expression on tumor cells is a strong positive prognostic marker in brain metastasis patients and positively associated with tumor-infiltrating T-lymphocytes (TILs). Whole DNA methylome analysis suggested that CD74 tumor cell expression might be regulated epigenetically via CD74 promoter methylation. CD74high and TILhigh tumors displayed a differential DNA methylation pattern with highest enrichment scores for antigen processing and presentation. Furthermore, CD74 knockdown in vitro lead to a reduction of HLA class II peptidome complexity, while HLA class I peptidome remained unaffected.In summary, our results demonstrate that a functional HLA class II processing machinery in brain metastatic tumor cells, reflected by a high expression of CD74 and a complex tumor cell HLA peptidome, seems to be crucial for better patient prognosis.

Impaired TGF-β induced growth inhibition contributes to the increased proliferation rate of neural stem cells harboring mutant p53

Gliomas have been classified according to their histological properties. However, their respective cells of origin are still unknown. Neural progenitor cells (NPC) from the subventricular zone (SVZ) can initiate tumors in murine models of glioma and are likely cells of origin in the human disease. In both, p53 signaling is often functionally impaired which may contribute to tumor formation. Also, TGF-beta, which under physiological conditions exerts a strong control on the proliferation of NPCs in the SVZ, is a potent mitogen on glioma cells. Here, we approach on the crosstalk between p53 and TGF-beta by loss of function experiments using NPCs derived from p53 mutant mice, as well as pharmacological inhibition of TGF-beta signaling using TGF-beta receptor inhibitors. NPC derived from p53 mutant mice showed increased clonogenicity and more rapid proliferation than their wildtype counterparts. Further, NPC derived from p53(mut/mut) mice were insensitive to TGF-beta induced growth arrest. Still, the canonical TGF-beta signaling pathway remained functional in the absence of p53 signaling and expression of key proteins as well as phosphorylation and nuclear translocation of SMAD2 were unaltered. TGF-beta-induced p21 expression could, in contrast, only be detected in p53(wt/wt) but not in p53(mut/mut) NPC. Conversely, inhibition of TGF-beta signaling using SB431542 increased proliferation of p53(wt/wt) but not of p53(mut/mut) NPC. In conclusion, our data suggest that the TGF-beta induced growth arrest in NPC depends on functional p53. Mutational inactivation of p53 hence contributes to increased proliferation of NPC and likely to the formation of hyperplasia of the SVZ observed in p53 deficient mice in vivo.

Urinary TIMP-1 and MMP-2 levels detect the presence of pancreatic malignancies

Background:

A majority of patients with pancreatic malignancies, including both pancreatic ductal adenocarcinoma (PDAC) and pancreatic neuroendocrine tumours (pNETs), present with advanced disease due to a lack of specific symptoms and current diagnostic limitations, making this disease extremely difficult to detect. Our goal was to determine whether urinary matrix metalloproteases (uMMPs) and/or their endogenous inhibitors, urinary tissue inhibitor of metalloproteases (uTIMPs), could be detected in the urine of patients with pancreatic malignancies and whether they may serve as independent predictors of disease status.

Methods:

Retrospective analyses of urine samples (n=139) from PDAC and pNET patients as well as age- and sex-matched controls were conducted. Urinary MMP-2 and uTIMP-1 levels were determined using ELISA and zymography. Biomarker expression in tumour and normal pancreatic tissues was analysed via immunohistochemistry (IHC).

Results:

Multivariable logistic regression analyses indicated that, when controlling for age and sex, uMMP-2 (P<0.0001) and uTIMP-1 (P<0.0001) but not uMMP-9, were significant independent predictors for distinguishing between PDAC patients and healthy controls. Our data also indicated that uMMP-2 was an independent predictor of the presence of pNET. In addition, uTIMP-1 levels could differentiate the two cancer groups, PDAC and pNET, respectively. Immunohistochemistry analysis confirmed that MMP-2 and TIMP-1 protein expression is significantly upregulated in PDAC tissue compared with the normal pancreas.

Conclusions:

Taken together, our results suggest that the detection of uMMP-2 and uTIMP-1 may have diagnostic value in the detection of pancreatic malignancies and that uTIMP-1 may be useful in distinguishing between pancreatic adenocarcinoma and neuroendocrine tumours.

Downregulation of AKT reverses platinum resistance of human ovarian cancers in vitro

Platinum resistance is the most crucial problem for treatment of ovarian cancer. Increasing evidence points towards AKT overexpression as a mechanistic reason for this clinical condition. The present study evaluates the effect of overexpression and downregulation of AKT on the sensitivity to cisplatin in a platinum-resistant human ovarian cancer cell line and the corresponding platinum-sensitive parental cell line. A2780 and A2780cis ovarian cancer cell lines were stably transfected with an AKT-sense and AKT-antisense plasmid. Successful transfection was evaluated by western blot analysis. Cytotoxic effects of cisplatin were evaluated by metabolic (MTT) and clonogenicity assays as well as by FACS analysis. AKT overexpression (confirmed by western blotting) converted platinum-sensitive A2780 into platinum-resistant cells as shown by MTT assay. Importantly, platinum resistance of A2780cis cells could be reversed by downregulation of AKT, as demonstrated by MTT and clonogenicity assays and FACS analysis. Our data provide strong evidence that cisplatin resistance in ovarian cancer is mediated by AKT overexpression and can be overcome by AKT downregulation, thus, providing a rationale for clinical phase II/III studies combining AKT inhibitors with cisplatin.

Toward the blood-borne miRNome of human diseases

In a multicenter study, we determined the expression profiles of 863 microRNAs by array analysis of 454 blood samples from human individuals with different cancers or noncancer diseases, and validated this 'miRNome' by quantitative real-time PCR. We detected consistently deregulated profiles for all tested diseases; pathway analysis confirmed disease association of the respective microRNAs. We observed significant correlations (P = 0.004) between the genomic location of disease-associated genetic variants and deregulated microRNAs.

The post-reproductive Fallopian tube: better removed?

Recently, the distal Fallopian tube has attracted considerable attention not only as site of origin for serous cancer in women with BRCA mutations, but also as the anatomical location where the majority of serous ovarian cancers apparently develop. Consequently, the Fallopian tube may be the unique location where early 'ovarian' cancers can be found--which would contradict the long-standing impression that the ovaries and the Fallopian tubes are always simultaneously involved. Based on the dismal prognosis associated with ovarian cancer and our inability to screen for early-stage disease, we discuss the rationale for introducing salpinges-hysterectomy as new clinical standard for women in need of hysterectomy and further weigh the arguments for and against bilateral salpingectomy as a sterilization method. There is no known physiological benefit of retaining the post-reproductive Fallopian tube during hysterectomy or sterilization, especially as this does not affect ovarian hormone production. On the other hand, the consequences associated with a surgical menopause provide a rationale for preserving the ovaries in premenopausal women. Prophylactic removal of the Fallopian tubes during hysterectomy or sterilization would rule out any subsequent tubal pathology, such as hydrosalpinx, which is observed in up to 30% of women after hysterectomy. Moreover, this intervention is likely to offer considerable protection against later tumour development, even if the ovaries are retained. Thus, we recommend that any hysterectomy should be combined with salpingectomy. In addition, women over 35 years of age could also be offered bilateral salpingectomy as means of sterilization.

Abstract PD02-05: Low Immunogenicity of Breast Cancer Stem Cells Leads to Selective Survival When Challenged with Trastuzumab and Natural Killer Cells

Although trastuzumab (Herceptin) has substantially improved the overall survival of patients with mammary carcinomas, even initially well-responding tumors often become resistant. Considering that clinical efficacy of trastuzumab correlates with the infiltration of natural killer (NK) cells into the tumor site, we established a cell-culture-system to select for ovarian cancer and mammary carcinoma cells that survive a challenge by trastuzumab and NK cells. Under these conditions, NK cells can eliminate tumor cells either via antibody-dependent-cell-mediatedcytotoxicity (ADCC) or by direct recognition of tumor-associated ligands for NKG2D or DNAM-1. The most striking phenotypic alteration observed in immunoselected ovarian cancer cells was a down-regulation of HER2 expression, leading to an ADCC-resistant phenotype. All breast cancer cells tested (MCF7, SK-BR-3, MDA-MB231, BT474), however, failed to develop resistance in vitro. Instead, treatment with trastuzumab and polyclonal NK-cells resulted in the preferential survival of individual sphere-forming cells that displayed a CD44highCD24low ‘'cancer-stem-celllike” phenotype (CSC) and expressed significantly less HER2 compared with non-stem cells. Moreover, the molecular determinants for the direct recognition of transformed cells, most notably the NKG2D ligands MICA, MICB, ULBP1-4 and the DNAM-1 ligands CD112 and CD155, were virtually absent from CSC.

When immunoseleced breast cancer cells were then re-expanded, they mostly lost the observed phenotype and regenerated a tumor cell culture that displayed initial HER2 surface expression and ADCC susceptibility, but was enriched in CD44highCD24low CSC. This translated into increased clonogenicity in vitro and tumorigenicity in vivo. We provide evidence that recruition of NK-cells and induction of ADCC by trastuzumab may spare actual tumor-initiating-cells, which could explain clinical relapse. Moreover, our observation that “relapsed” in vitro cultures show identical HER2 surface expression and susceptibility toward ADCC suggests that administration of trastuzumab beyond relapse might be considered, especially when combined with proteasome inhibition which increase the expression of NKG2D ligands.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD02-05.

Whole blood-derived miRNA profiles as potential new tools for ovarian cancer screening

BACKGROUND

Screening is an unsolved problem for ovarian cancer (OvCA). As late detection is equivalent to poor prognosis, we analysed whether OvCA patients show diagnostically meaningful microRNA (miRNA) patterns in blood cells.

METHODS

Blood-borne whole miRNome profiles from 24 patients with OvCA and 15 age- and sex-matched healthy controls were biostatistically evaluated.

RESULTS

Student's t-test revealed 147 significantly deregulated miRNAs before and 4 after Benjamini-Hochberg adjustment. Although these included miRNAs already linked to OvCA (e.g., miR-16, miR-155), others had never before been connected to specific diseases. A bioinformatically calculated miRNA profile allowed for discrimination between blood samples of OvCA patients and healthy controls with an accuracy of >76%. When only cancers of the serous subtype were considered and compared with an extended control group (n=39), accuracy, specificity and sensitivity all increased to >85%.

CONCLUSION

Our proof-of-principle study strengthens the hypothesis that neoplastic diseases generate characteristic miRNA fingerprints in blood cells. Still, the obtained OvCA-associated miRNA pattern is not yet sensitive and specific enough to permit the monitoring of disease progression or even preventive screening. Microarray-based miRNA profiling from peripheral blood could thus be combined with other markers to improve the notoriously difficult but important screening for OvCA.

Shigella mediated depletion of macrophages in a murine breast cancer model is associated with tumor regression

A tumor promoting role of macrophages has been described for a transgenic murine breast cancer model. In this model tumor-associated macrophages (TAMs) represent a major component of the leukocytic infiltrate and are associated with tumor progression. Shigella flexneri is a bacterial pathogen known to specificly induce apotosis in macrophages. To evaluate whether Shigella-induced removal of macrophages may be sufficient for achieving tumor regression we have developed an attenuated strain of S. flexneri (M90TΔaroA) and infected tumor bearing mice. Two mouse models were employed, xenotransplantation of a murine breast cancer cell line and spontanous breast cancer development in MMTV-HER2 transgenic mice. Quantitative analysis of bacterial tumor targeting demonstrated that attenuated, invasive Shigella flexneri primarily infected TAMs after systemic administration. A single i.v. injection of invasive M90TΔaroA resulted in caspase-1 dependent apoptosis of TAMs followed by a 74% reduction in tumors of transgenic MMTV-HER-2 mice 7 days post infection. TAM depletion was sustained and associated with complete tumor regression.

These data support TAMs as useful targets for antitumor therapy and highlight attenuated bacterial pathogens as potential tools.

Stem cells, melanoma and cancer stem cells: the good, the bad and the evil?

Most cancers contain morphologically heterogeneous populations of cells. While this observation may partly be explained by the coexistence of multiple genetic sub-clones arising through independent somatic mutations and/or as a result of differentiation processes in the tumor microenvironment, it also implies that the tumor may be formed from undifferentiated ''stem cell-like'' cells called ''cancer stem cells'' or ''cancer-initiating cells''. These cells are thought to constitute one or several rare subpopulations in a given tumor and would be strongly responsible for initiation of tumor development and growth as well as for metastasis and recurrence after cytoreductive therapy. However, while the concept of cancer stem cells has been first established for human myeloid leukemia in the 1960s, it has only much later been extended to other solid tumors such as breast or brain cancers and most recently to melanoma. Thus, it is presently unclear which role a sufficiently characterized population of melanoma stem cells plays in cancer promotion and progression. Here, we review the emerging melanoma stem cell model and discuss the biological and therapeutic implications of the model.

The role of regulatory T cells in ovarian cancer

Regulatory T cells (T(reg)), also termed suppressor T cells, control self-reactive T cells in the periphery, thereby conferring protection against immunologic self-destruction. While T(reg) are essential for the prevention of autoimmunity, they also inhibit immune responses against tumor antigens. This is corroborated by an increased mortality rate associated with the presence of a high number of intratumoral T(reg). Tumor infiltration by non-T(reg), on the other hand, is predictive for a substantially longer patient survival. These clinical data suggest that ovarian cancer patients can spontaneously mount effective antitumor immune responses that are undermined by T(reg)-mediated tolerization. The present article reviews clinical and experimental findings on T(reg) in ovarian cancer, with special regard to potential therapeutic implications, which may result from the existing evidence.

PCTAIRE3: a putative mediator of growth arrest and death induced by CTS-1, a dominant-positive p53-derived synthetic tumor suppressor, in human malignant glioma cells

Chimeric tumor suppressor-1 (CTS-1) is based on the sequence of p53 and was designed as a therapeutic tool resisting various mechanisms of p53 inactivation. We previously reported that an adenovirus expressing CTS-1 (Ad-CTS-1) has superior cell death-inducing activity in glioma cells compared with wild-type p53. Here, we used cDNA microarrays to detect changes in gene expression preferentially induced by Ad-CTS-1. The putative serine threonine kinase, PCTAIRE3, and the quinone oxireductase, PIG3, were strongly induced by Ad-CTS-1 compared with wild-type p53. An adenoviral vector encoding PCTAIRE3 (Ad-PCTAIRE3) induced growth arrest and killed a minor proportion of the glioma cells. Ad-PIG3 alone affected neither growth nor viability. However, coinfection with Ad-PCTAIRE3 and Ad-PIG3 resulted in enhanced growth inhibition compared with Ad-PCTAIRE3 infection alone. Ad-CTS1, Ad-PCTAIRE3 or Ad-PIG3 induced the formation of free reactive oxygen species (ROS). However, the prevention of ROS formation induced by Ad-PCTAIRE3 and Ad-CTS-1 did not block growth arrest and cell death, suggesting that ROS formation is not essential for these effects. Altogether, these data identify PCTAIRE3 as one novel growth-inhibitory and death-inducing p53 response gene and suggest that changes in the expression of specific target genes contribute to the superior anti-glioma activity of CTS-1.

Alkylphosphocholine-induced glioma cell death is BCL-XL-sensitive, caspase-independent and characterized by massive cytoplasmic vacuole formation

Alkylphosphocholines (APC) are candidate anticancer agents. We here report that APC induce the formation of large vacuoles and typical features of apoptosis in human glioma cell lines, but not in immortalized astrocytes. APC promote caspase activation, poly(ADP-ribose)-polymerase (PARP) processing and cytochrome c release from mitochondria. Adenoviral X-linked inhibitor of apoptosis (XIAP) gene transfer, or exposure to the caspase inhibitor, benzyloxycarbonyl-Val-Ala-DL-Asp-fluoro-methylketone zVAD-fmk, blocks caspase-7 and PARP processing, but not cell death, whereas BCL-X(L) blocks not only caspase-7 and PARP processing but also cell death. APC induce changes in Delta Psi m in sensitive glioma cells, but not in resistant astrocytes. The changes in Delta Psi m are unaffected by crm-A (cowpox serpin-cytokine response modifier protein A), XIAP or zVAD-fmk, but blocked by BCL-X(L), and are thus a strong predictor of cell death in response to APC. Free radicals are induced, but not responsible for cell death. APC thus induce a characteristic morphological, BCL-X(L)-sensitive, apparently caspase-independent cell death involving mitochondrial alterations selectively in neoplastic astrocytic cells.

CP-31398, a novel p53-stabilizing agent, induces p53-dependent and p53-independent glioma cell death

CP-31398 is a prototype small molecule that stabilizes the active conformation of p53 and promotes p53 activity in cancer cell lines with mutant or wild-type p53. Here, we report that CP-31398 induces p53 reporter gene activity and p21 expression in all of 11 glioma cell lines harboring wild-type or mutant p53, but not in p53-null LN-308 cells. Upon prolonged exposure to CP-31398, all glioma cell lines undergo caspase-independent and bcl-x(L)-insensitive cell death with EC(50) concentrations of 10-36 microM. By comparing p53 wild-type U87MG and p53-null LN-308 cells expressing the temperature-sensitive p53(V135A) mutant, we delineate two pathways of CP-31398-induced cell death: an early, p53-dependent pathway that requires (new p53) protein synthesis and a late, p53-independent pathway characterized by aurintricarboxylic acid -sensitive calcium release and epiphenomenal free radical formation. Post-transcriptional repression of p53 synthesis by an intracellularly transcribed short interfering RNA confirmed the presence of these two pathways of cell death. These observations point out some of the liabilities of CP-31398 as a prototype p53-based therapeutic and define a rationale for further refinement of small molecules that specifically target the p53 pathway, but lack the p53-independent effects.

The non-classical MHC molecule HLA-G protects human muscle cells from immune-mediated lysis: implications for myoblast transplantation and gene therapy

HLA-G is a non-classical MHC class I molecule with highly limited tissue distribution which has been attributed chiefly immune-regulatory functions. We previously have reported that HLA-G is expressed in inflamed muscle in vivo and by cultured myoblasts in vitro. Here, we used the in vitro models of human myoblasts or TE671 muscle rhabdomyosarcoma cells to characterize the functional role of HLA-G for muscle immune cell interactions. Gene transfer of the two major isoforms of HLA-G (transmembranous HLA-G1 and soluble HLA-G5) into TE671 rendered these cells resistant to alloreactive lysis by direct inhibition of natural killer (NK) cells, and CD4 and CD8 T cells. Further, HLA-G reduced alloproliferation, interfered with effective priming of antigen-specific cytotoxic T cells and reduced antigen-specific alloreactive lysis. HLA-G pre-induced on cultured myoblasts inhibited lysis by alloreactive peripheral blood mononuclear cells. This protection was reversed by a neutralizing HLA-G antibody. Interestingly, a few HLA-G-positive cells within a population of HLA-G-negative muscle target cells conveyed significant inhibitory effects on alloreactive lysis. Our results reveal further insights into the immunobiology of muscle and suggest that ectopic expression of HLA-G may promote the survival of transplanted myoblasts in the future treatment of hereditary muscle diseases. Further, HLA-G could represent a novel self-derived anti-inflammatory principle applicable in strategies against inflammatory aggression.