Trastuzumab Activates Allogeneic or Autologous Antibody-Dependent Cellular Cytotoxicity against Malignant Rhabdoid Tumor Cells and Interleukin-2 Augments the Cytotoxicity

Recent insights into the SWI/SNF complex and the molecular mechanism of hSNF5 deficiency in rhabdoid tumors

Genetic information encoded by DNA is packaged in the nucleus using the chromatin structure. The accessibility of transcriptional elements in DNA is controlled by the dynamic structural changes of chromatin for the appropriate regulation of gene transcription. Chromatin structure is regulated by two general mechanisms, one is histone modification and the other is chromatin remodeling in an ATP-dependent manner. Switch/sucrose nonfermentable (SWI/SNF) complexes utilize the energy from ATP hydrolysis to mobilize nucleosomes and remodel the chromatin structure, contributing to conformational changes in chromatin. Recently, the inactivation of encoding genes for subunits of the SWI/SNF complexes has been documented in a series of human cancers, accounting for up to almost 20% of all human cancers. For example, human SNF5 (hSNF5), the gene that encodes a subunit of the SWI/SNF complexes, is the sole mutation target that drives malignant rhabdoid tumors (MRT). Despite remarkably simple genomes, the MRT has highly malignant characteristics. As a key to understanding MRT tumorigenesis, it is necessary to fully examine the mechanism of chromatin remodeling by the SWI/SNF complexes. Herein, we review the current understanding of chromatin remodeling by focusing on SWI/SNF complexes. In addition, we describe the molecular mechanisms and influences of hSNF5 deficiency in rhabdoid tumors and the prospects for developing new therapeutic targets to overcome the epigenetic drive of cancer that is caused by abnormal chromatin remodeling.

Validation of a non-oncogene encoded vulnerability to exportin 1 inhibition in pediatric renal tumors

BACKGROUND

Malignant rhabdoid tumors (MRTs) and Wilms' tumors (WTs) are rare and aggressive renal tumors of infants and young children comprising ∼5% of all pediatric cancers. MRTs are among the most genomically stable cancers, and although WTs are genomically heterogeneous, both generally lack therapeutically targetable genetic mutations.

METHODS

Comparative protein activity analysis of MRTs (n = 68) and WTs (n = 132) across TCGA and TARGET cohorts, using metaVIPER, revealed elevated exportin 1 (XPO1) inferred activity. In vitro studies were performed on a panel of MRT and WT cell lines to evaluate effects on proliferation and cell-cycle progression following treatment with the selective XPO1 inhibitor selinexor. In vivo anti-tumor activity was assessed in patient-derived xenograft (PDX) models of MRTs and WTs.

FINDINGS

metaVIPER analysis identified markedly aberrant activation of XPO1 in MRTs and WTs compared with other tumor types. All MRT and most WT cell lines demonstrated baseline, aberrant XPO1 activity with in vitro sensitivity to selinexor via cell-cycle arrest and induction of apoptosis. In vivo, XPO1 inhibitors significantly abrogated tumor growth in PDX models, inducing effective disease control with sustained treatment. Corroborating human relevance, we present a case report of a child with multiply relapsed WTs with prolonged disease control on selinexor.

CONCLUSIONS

We report on a novel systems-biology-based comparative framework to identify non-genetically encoded vulnerabilities in genomically quiescent pediatric cancers. These results have provided preclinical rationale for investigation of XPO1 inhibitors in an upcoming investigator-initiated clinical trial of selinexor in children with MRTs and WTs and offer opportunities for exploration of inferred XPO1 activity as a potential predictive biomarker for response.

FUNDING

This work was funded by CureSearch for Children's Cancer, Alan B. Slifka Foundation, NIH (U01 CA217858, S10 OD012351, and S10 OD021764), Michael's Miracle Cure, Hyundai Hope on Wheels, Cannonball Kids Cancer, Conquer Cancer the ASCO Foundation, Cycle for Survival, Paulie Strong Foundation, and the Grayson Fund.

CD146 is a novel marker for highly tumorigenic cells and a potential therapeutic target in malignant rhabdoid tumor

Malignant rhabdoid tumor (MRT) is a rare, highly aggressive pediatric malignancy that primarily develops during infancy and early childhood. Despite the existing standard of intensive multimodal therapy, the prognosis of patients with MRT is dismal; therefore, a greater understanding of the biology of this disease is required to establish novel therapies. In this study, we identified a highly tumorigenic sub-population in MRT, based on the expression of CD146 (also known as melanoma cell adhesion molecule), a cell adhesion molecule expressed by neural crest cells and various derivatives. CD146⁺ cells isolated from four MRT cell lines by cell sorting exhibited enhanced self-renewal and invasive potential in vitro. In a xenograft model using immunodeficient NOD/Shi-scid IL-2Rγ-null mice, purified CD146⁺ cells obtained from MRT cell lines or a primary tumor exhibited the exclusive ability to form tumors in vivo. Blocking of CD146-related mechanisms, either by short hairpin RNA knockdown or treatment with a polyclonal antibody against CD146, effectively suppressed tumor growth of MRT cells both in vitro and in vivo via induction of apoptosis by inactivating Akt. Furthermore, CD146 positivity in immunohistological analysis of 11 MRT patient samples was associated with poor patient outcomes. These results suggest that CD146 defines a distinct sub-population in MRT with high tumorigenic capacity and that this marker represents a promising therapeutic target.

Genome-Wide Profiles of Extra-cranial Malignant Rhabdoid Tumors Reveal Heterogeneity and Dysregulated Developmental Pathways

Malignant rhabdoid tumors (MRTs) are rare lethal tumors of childhood that most commonly occur in the kidney and brain. MRTs are driven by SMARCB1 loss, but the molecular consequences of SMARCB1 loss in extra-cranial tumors have not been comprehensively described and genomic resources for analyses of extra-cranial MRT are limited. To provide such data, we used whole-genome sequencing, whole-genome bisulfite sequencing, whole transcriptome (RNA-seq) and microRNA sequencing (miRNA-seq), and histone modification profiling to characterize extra-cranial MRTs. Our analyses revealed gene expression and methylation subgroups and focused on dysregulated pathways, including those involved in neural crest development.

SNF5 reexpression in malignant rhabdoid tumors regulates transcription of target genes by recruitment of SWI/SNF complexes and RNAPII to the transcription start site of their promoters

Malignant rhabdoid tumor (MRT), a highly aggressive cancer of young children, displays inactivation or loss of the hSNF5/INI1/SMARCB1 gene, a core subunit of the SWI/SNF chromatin-remodeling complex, in primary tumors and cell lines. We have previously reported that reexpression of hSNF5 in some MRT cell lines causes a G1 arrest via p21(CIP1/WAF1) (p21) mRNA induction in a p53-independent manner. However, the mechanism(s) by which hSNF5 reexpression activates gene transcription remains unclear. We initially searched for other hSNF5 target genes by asking whether hSNF5 loss altered regulation of other consensus p53 target genes. Our studies show that hSNF5 regulates only a subset of p53 target genes, including p21 and NOXA, in MRT cell lines. We also show that hSNF5 reexpression modulates SWI/SNF complex levels at the transcription start site (TSS) at both loci and leads to activation of transcription initiation through recruitment of RNA polymerase II (RNAPII) accompanied by H3K4 and H3K36 modifications. Furthermore, our results show lower NOXA expression in MRT cell lines compared with other human tumor cell lines, suggesting that hSNF5 loss may alter the expression of this important apoptotic gene. Thus, one mechanism for MRT development after hSNF5 loss may rely on reduced chromatin-remodeling activity of the SWI/SNF complex at the TSS of critical gene promoters. Furthermore, because we observe growth inhibition after NOXA expression in MRT cells, the NOXA pathway may provide a novel target with clinical relevancy for treatment of this aggressive disease.

Fetal and Neonatal Illnesses Caused or Influenced by Maternal Transplacental IgG and/or Therapeutic Antibodies Applied During Pregnancy

The human fetus is protected by the mother’s antibodies. At the end of the pregnancy, the concentration of maternal antibodies is higher in the cord blood, than in the maternal circulation. Simultaneously, the immune system of the fetus begins to work and from the second trimester, fetal IgM is produced by the fetal immune system specific to microorganisms and antigens passing the maternal-fetal barrier. The same time the fetal immune system has to cope and develop tolerance and T_REG cells to the maternal microchimeric cells, latent virus-carrier maternal cells and microorganisms transported through the maternal-fetal barrier.

The maternal phenotypic inheritance may hide risks for the newborn, too. Antibody mediated enhancement results in dengue shock syndrome in the first 8 month of age of the baby.

A series of pathologic maternal antibodies may elicit neonatal illnesses upon birth usually recovering during the first months of the life of the offspring. Certain antibodies, however, may impair the fetal or neonatal tissues or organs resulting prolonged recovery or initiating prolonged pathological processes of the children.

The importance of maternal anti-idiotypic antibodies are believed to prime the fetal immune system with epitopes of etiologic agents infected the mother during her whole life before pregnancy and delivery.

The chemotherapeutical and biological substances used for the therapy of the mother will be transcytosed into the fetal body during the last two trimesters of pregnancy. The long series of the therapeutic monoclonal antibodies and conjugates has not been tested systematically yet. The available data are summarised in this chapter.

The innate immunity plays an important role in fetal defence. The concentration of interferon is relative high in the placenta. This is probably one reason, why the therapeutic interferon treatment of the mother does not impair the fetal development.

Novel Toll-like receptor-4 deficiency attenuates trastuzumab (Herceptin) induced cardiac injury in mice

Background

Cardiac inflammation and generation of oxidative stress are known to contribute to trastuzumab (herceptin) induced cardiac toxicity. Toll-like receptors (TLRs) are a part of the innate immune system and are involved in cardiac stress reactions. Since TLR4 might play a relevant role in cardiac inflammatory signaling, we investigated whether or not TLR4 is involved in trastuzumab induced cardiotoxicity.

Methods

Seven days after a single injection of herceptin (2 mg/kg; i.p.), left ventricular pressure volume loops were measured in HeN compotent (TLR4^+/+) and HeJ mutant (TLR4^-/-) treated with trastuzumab and control mice. Immunofluorescent staining for monocyte infiltration and analyses of plasma by (ELISAs) for different chemokines including: MCP-1and tumor necrosis factor-α (TNF-α), Western immunoblotting assay for ICAM-1, and used troponin I for cardiac injury marker.

Results

Trastuzumab injection resulted in an impairment of left ventricular function in TLR-4 competent (HeN), in contrast TLR4^-/^- trastuzumab mice showed improved left ventricular function EF%, CO; p < 0.05, attenuation of mononuclear cell infiltration in TLR4 ^-/-; p < 0.05 vs.TLR-4 competent (HeN), reduced level of cytokines TNF-α, MCP-1 and ICAM-1 expression in TLR4^-/-, marked reduction of myocardial troponin-I levels in TLR4-deficient mice. Data are presented as means ± SE; n = 8 in each group p < 0.05 vs.TLR-4 competent (HeN).

Conclusions

Treatment with trastuzumab induces an inflammatory response that contributes to myocardial tissue TLR4 mediates chemokine expression (TNF-α, MCP-1and ICAM-1), so in experimental animals TLR4 deficiency improves left ventricular function and attenuates pathophysiological key mechanisms in trastuzumab induced cardiomyopathy.

Sensitivity of malignant rhabdoid tumor cell lines to PD 0332991 is inversely correlated with p16 expression

Malignant rhabdoid tumor (MRT) is a rare and highly aggressive neoplasm of young children. MRT is characterized by inactivation of integrase interactor 1 (INI1). Cyclin-dependent kinase 4 (CDK4), which acts downstream of INI1, is required for the proliferation of MRT cells. Here we investigated the effects of PD 0332991 (PD), a potent inhibitor of CDK4, against five human MRT cell lines (MP-MRT-AN, KP-MRT-RY, G401, KP-MRT-NS, KP-MRT-YM). In all of the cell lines except KP-MRT-YM, PD inhibited cell proliferation >50%, (IC(50) values 0.01 to 0.6 μM) by WST-8 assay, and induced G1-phase cell cycle arrest, as shown by flow cytometry and BrdU incorporation assay. The sensitivity of the MRT cell lines to PD was inversely correlated with p16 expression (r=0.951). KP-MRT-YM cells overexpress p16 and were resistant to the growth inhibitory effect of PD. Small interfering RNA against p16 significantly increased the sensitivity of KP-MRT-YM cells to PD (p<0.05). These results suggest that p16 expression in MRT could be used to predict its sensitivity to PD. PD may be an attractive agent for patients with MRT whose tumors express low levels of p16.

Tumour exosomes inhibit binding of tumour-reactive antibodies to tumour cells and reduce ADCC

In order to grow within an immunocompetent host, tumour cells have evolved various strategies to cope with the host's immune system. These strategies include the downregulation of surface molecules and the secretion of immunosuppressive factors like IL-10 and PGE2 that impair the maturation of immune effector cells, among other mechanisms. Recently, tumour exosomes (TEX) have also been implicated in tumour-induced immune suppression as it has been shown that TEX can induce apoptosis in T lymphocytes. In this study, we extend our knowledge about immunosuppressive features of these microvesicles in that we show that TEX efficiently bind and sequester tumour-reactive antibodies and dramatically reduce their binding to tumour cells. Moreover, we demonstrate that this antibody sequestration reduces the antibody-dependent cytotoxicity by immune effector cells, which is among the most important anti-tumour reactions of the immune system and a significant activity of therapeutic antibodies. Taken together, these data point to the fact that tumour-derived exosomes interfere with the tumour-specific function of immune cells and constitute an additional mechanism how tumours escape from immune surveillance.

Congenital anomalies and rhabdoid tumor associated with 22q11 germline deletion and somatic inactivation of the SMARCB1 tumor suppressor

The most common microdeletion in humans involves the 22q11 region. Congenital anomalies associated with 22q11 loss include cardiac and facial defects. Less frequent is the co-presentation of malignant rhabdoid tumors that are highly aggressive childhood malignancies typically found in renal or extra-renal soft tissues and central nervous system. A newborn patient presented with multiple congenital anomalies consistent with 22q11 deletion syndrome including cleft lip and palate, ear tags and ventricular septal defects co-presenting with an axillary rhabdoid tumor. Comparative genomic hybridization revealed a 2.8 Mb germline deletion in the 22q11.2 region containing genes required for normal fetal development and the SMARCB1 tumor suppressor gene. Analysis of tumor DNA revealed a somatic deletion of exon 7 in the second allele of SMARCB1. Expression of SMARCB1 was absent, while tumor markers including MYC, GFAP, and CLAUDIN-6 were upregulated. The presence of tandem oriented BCRL modules located within interspersed low copy repeat elements throughout the 22q11 distal region may predispose this area for microdeletions through nonalleleic homologous recombination.

Clinical and pathological features of paediatric malignant rhabdoid tumours

BACKGROUND

Malignant rhabdoid tumours (MRT) and their central nervous system (CNS) counterparts atypical teratoid/rhabdoid tumours (ATRT) are rare, highly aggressive malignant neoplasms of childhood. Although there are isolated reports of long-term survival with intensive, multimodal therapy, outcomes are generally poor.

PROCEDURE

We conducted a retrospective review of all patients diagnosed with MRT/ATRT at Great Ormond Street Hospital over the 20 years from 1989 to 2009. All cases were subjected to expert pathological review including INI-1 immunostaining.

RESULTS

In a final cohort of 34 cases, overall survival was 17.4%, with median survival 10.1 months. Outcome in patients aged <3 years was significantly worse (median survival 6.2 months vs. 19.2 months). Data demonstrated a statistically significant benefit of radiotherapy (median survival 14.9 months vs. 6.6 months), although this analysis is confounded by the impact of patient age. There were four long-term survivors (>30 months), all of whom received chemotherapy with or without surgical resection or radiotherapy. In the present study, immunohistochemistry revealed no significant staining for either c-Erb or c-Met in any case, suggesting that targeting these molecules is unlikely to be of benefit in treating MRT/ATRT.

CONCLUSIONS

In view of poor outcomes, there is a clear need for new treatment strategies and the identification of novel molecular targets for MRT/ATRT.

Immunoselection of breast and ovarian cancer cells with trastuzumab and natural killer cells: selective escape of CD44high/CD24low/HER2low breast cancer stem cells

Although trastuzumab (Herceptin) has substantially improved the overall survival of patients with mammary carcinomas, even initially well-responding tumors often become resistant. Because natural killer (NK) cell-mediated antibody-dependent cell-mediated cytotoxicity (ADCC) is thought to contribute to the therapeutic effects of trastuzumab, we have established a cell culture system to select for ADCC-resistant SK-OV-3 ovarian cancer and MCF7 mammary carcinoma cells. Ovarian cancer cells down-regulated HER2 expression, resulting in a more resistant phenotype. MCF7 breast cancer cells, 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 CD44(high)CD24(low) "cancer stem cell-like" phenotype and expressed significantly less HER2 compared with non-stem cells. Likewise, the CD44(high)CD24(low) population was also found to be more immunoresistant in SK-BR3, MDA-MB231, and BT474 breast cancer cell lines. When immunoselected MCF7 cells were then re-expanded, they mostly lost the observed phenotype to regenerate a tumor cell culture that displayed the initial HER2 surface expression and ADCC-susceptibility, but was enriched in CD44(high)CD24(low) cancer stem cells. This translated into increased clonogenicity in vitro and tumorigenicity in vivo. Thus, we provide evidence that the induction of ADCC by trastuzumab and NK cells may spare the actual tumor-initiating cells, which could explain clinical relapse and progress. Moreover, our observation that the "relapsed" in vitro cultures show practically identical HER2 surface expression and susceptibility toward ADCC suggests that the administration of trastuzumab beyond relapse might be considered, especially when combined with an immune-stimulatory treatment that targets the escape variants.

Identification and metastatic potential of tumor-initiating cells in malignant rhabdoid tumor of the kidney

PURPOSE

Malignant rhabdoid tumor of the kidney (MRTK) is a rare and highly aggressive malignancy of infanthood. In an effort to delineate MRTK progression, we investigated the metastatic fate of some MRTK cells using xenotransplantation animal models and the tumor-initiating potential of CD133(+) MRTK cells.

EXPERIMENTAL DESIGN

We established two MRTK cell lines (JMU-RTK-1 and JMU-RTK-2) from patients with MRTK. We generated five luciferase-expressing MRTK cells for in vivo luminescent imaging and evaluated the metastatic fate in an orthotopic xenotransplantation model. Capacities of MRTK-initiating cells were examined in nonobese diabetic/severe combined immunodeficient mice after antibody-mediated magnetic bead sorting. Use of chemokine receptor CXCR4 expression as a metastatic marker was evaluated by flow cytometry and Western blotting.

RESULTS

MRTK cell lines showed distant organ metastasis. JMU-RTK-1, JMU-RTK-2, and G401 cells showed considerable aggressiveness compared with SWT-1 and SWT-2 cells (P < 0.05). Moreover, as few as 1,000 CD133(+) MRTK cells initiated tumor development in nonobese diabetic/severe combined immunodeficient mice by 21 days (60-100%) in all examined cell lines, although the same number of CD133(-) MRTK cells could not form tumors (0%). Interestingly, the metastatic potential of the CD133(+) population remained unaffected compared with a nonenriched population. The potential metastatic marker CXCR4 was expressed in CD133(+) and CD133(-) MRTK cells, and CD133(-) cells seemed to play a cooperative role in terms of tumorigenicity and metastasis.

CONCLUSIONS

These results suggest that CD133(+) cells may determine the metastatic fate of MRTK cells and that CD133(-) cells may play an auxiliary role in tumor progression and metastasis.