Acquired Resistance to EZH2 Inhibitor GSK343 Promotes the Differentiation of Human DLBCL Cell Lines toward an ABC-Like Phenotype

Diffuse large B-cell lymphoma (DLBCL) accounts for 40% of non-Hodgkin lymphoma, and 30% to 40% of patients will succumb to relapsed/refractory disease (rrDLBCL). Patients with rrDLBCL generally have low long-term survival rates due to a lack of efficient salvage therapies. Small-molecule inhibitors targeting the histone methyltransferase EZH2 represent an emerging group of novel therapeutics that show promising clinical efficacy in patients with rrDLBCL. The mechanisms that control acquired resistance to this class of targeted therapies, however, remain poorly understood. Here, we develop a model of resistance to the EZH2 inhibitor (EZH2i) GSK343 and use RNA-seq data and in vitro investigation to show that GCB (germinal center B-cell)-DLBCL cell lines with acquired drug resistance differentiate toward an ABC (activated B-cell)-DLBCL phenotype. We further observe that the development of resistance to GSK343 is sufficient to induce cross-resistance to other EZH2i. Notably, we identify the immune receptor SLAMF7 as upregulated in EZH2i-resistant cells, using chromatin immunoprecipitation profiling to uncover the changes in chromatin landscape remodeling that permit this altered gene expression. Collectively, our data reveal a previously unreported response to the development of EZH2i resistance in DLBCL, while providing strong rationale for pursuing investigation of dual-targeting of EZH2 and SLAMF7 in rrDLBCL.

Two-year survival with nivolumab in previously treated advanced non-small-cell lung cancer: A real-world pooled analysis of patients from France, Germany, and Canada

OBJECTIVES

Immune checkpoint inhibitors have become the standard of care for metastatic non-small-cell lung cancer (NSCLC) progressing during or after platinum-based chemotherapy. Real-world clinical practice tends to represent more diverse patient characteristics than randomized clinical trials. We sought to evaluate overall survival (OS) outcomes in the total study population and in key subsets of patients who received nivolumab for previously treated advanced NSCLC in real-world settings in France, Germany, or Canada.

MATERIALS AND METHODS

Data were pooled from two prospective observational cohort studies, EVIDENS and ENLARGE, and a retrospective registry in Canada. Patients included in this analysis were aged ≥18 years, had stage IIIB/IV NSCLC, and received nivolumab after at least one prior line of systemic therapy. OS was estimated in the pooled population and in various subgroups using the Kaplan-Meier method. Timing of data collection varied across cohorts (2015-2019).

RESULTS

Of the 2585 patients included in this analyses, 1235 (47.8 %) were treated in France, 881 (34.1 %) in Germany, and 469 (18.1 %) in Canada. Median OS for the total study population was 11.3 months (95 % CI: 10.5-12.2); this was similar across France, Germany, and Canada. The OS rate was 49 % at 1 year and 28 % at 2 years for the total study population. In univariable Cox analyses, the presence of epidermal growth factor receptor mutations in nonsquamous disease, liver, or bone metastases were associated with significantly shorter OS, whereas tumor programmed death ligand 1 expression and Eastern Cooperative Oncology Group performance status 0-1 were associated with significantly prolonged OS. Similar OS was noted across subgroups of age and prior lines of therapy.

CONCLUSION

OS rates in patients receiving nivolumab for previously treated advanced NSCLC in real-world clinical practice closely mirrored those in phase 3 studies, suggesting similar effectiveness of nivolumab in clinical trials and clinical practice.

Two-year survival with nivolumab in previously treated, advanced non-small cell lung cancer: A pooled analysis of real-world patients from France, Germany and Canada

e21714

Background: Data from clinical studies demonstrate a long-term survival benefit of nivolumab in previously treated advanced non-small cell lung cancer (NSCLC) patients with overall survival (OS) at two-years of 27%, however real-world data are limited. We report OS in patients pooled from two prospective multi-centre observational cohort studies in France (EVIDENS, NCT03382496) and Germany (ENLARGE, NCT02910999) and a third retrospective registry of patients treated through expanded access to nivolumab in Canada. Methods: Individual patient data from each cohort were pooled and harmonised in eligibility criteria and variable definitions. Included patients had locally advanced or metastatic (stage IIIB/IV) NSCLC, received nivolumab after at least one prior systemic therapy and had no other concurrent primary cancers. OS was estimated from nivolumab initiation until death or censoring using Kaplan-Meier method. Equality of survival distributions across cohorts was measured using log-rank test. Hazard ratios (HR) with 95% confidence intervals (CI) were calculated from unstratified Cox proportional hazards regression models to explore survival among subgroups. Data on bone and liver metastases, PD-L1 and safety were available and analysed for France and Germany only. Results: Data from 2582 patients (48% France; 34% Germany; 18% Canada) were pooled. Baseline characteristics were: median age 66 years, 64% male, 82% ECOG 0-1, 69% 1 prior line of therapy, 68% non-squamous histology, and 18% with brain metastases (treated or untreated). Median follow-up was 8 months. No difference in OS was observed between countries. The 2-year OS was 28% (95%CI 25-31) for all patients, 26% (95%CI 21-31) for squamous histology and 29% (95%CI 26-33) for non-squamous histology. Bone metastases (HR 1.42; 95%CI 1.26-1.60; P= < .0001) and liver metastases (HR 1.60; 95%CI 1.39-1.85; P= < .0001) were associated with shorter survival, while ECOG PS 0-1 (HR 0.61; 95%CI 0.52-0.71; P= < .0001) and PD-L1 positivity (HR 0.75; 95%CI 0.60-0.93; P= < .0001) were associated with prolonged survival. Rates of any grade and grade 3/4 treatment-related adverse events (TRAE) were 32% and 7% respectively. Conclusions: In this three-country pooled analysis of nivolumab in previously treated advanced NSCLC, real-world overall survival at 2-years was consistent with pivotal nivolumab trials overall and in subgroups. Rates of grade 3/4 TRAEs were comparable, but events of lower grade may be underreported in the real world.

Real-world benefit of nivolumab in a Canadian non-small-cell lung cancer cohort

Background

Nivolumab was the first immuno-oncology agent available for the treatment of lung cancer in Canada. In the present study, we evaluated the real-world benefit of nivolumab in Canadian patients with lung cancer.

Methods

Patients included in the cohort were identified from a registry of patients treated through expanded access to nivolumab before and after Health Canada approval. Demographics were collected from the application forms. Outcome data for the duration of treatment and survival were collected retrospectively.

Results

In contrast to the randomized clinical trial populations, our study cohort included patients who were older (median age: 66 years; range: 36-92 years) and who had an Eastern Cooperative Oncology Group performance status of 2 (8.9%). Despite the poorer-prognosis cohort, median overall survival was 12.0 months, which is comparable to the survival demonstrated in the randomized phase iii trials of nivolumab in lung cancer. Median time to treatment discontinuation was 3.45 months and was similar for all patient subgroups, including poorer-prognosis groups such as those with a performance status of 2, those 75 years of age and older, and those with brain metastases.

Conclusions

Nivolumab given in a real-world clinical setting was associated with results similar to those reported in the phase iii clinical trial setting.

The eukaryotic translation initiation factor eIF4E harnesses hyaluronan production to drive its malignant activity

The microenvironment provides a functional substratum supporting tumour growth. Hyaluronan (HA) is a major component of this structure. While the role of HA in malignancy is well-defined, the mechanisms driving its biosynthesis in cancer are poorly understood. We show that the eukaryotic translation initiation factor eIF4E, an oncoprotein, drives HA biosynthesis. eIF4E stimulates production of enzymes that synthesize the building blocks of HA, UDP-Glucuronic acid and UDP-N-Acetyl-Glucosamine, as well as hyaluronic acid synthase which forms the disaccharide chain. Strikingly, eIF4E inhibition alone repressed HA levels as effectively as directly targeting HA with hyaluronidase. Unusually, HA was retained on the surface of high-eIF4E cells, rather than being extruded into the extracellular space. Surface-associated HA was required for eIF4E’s oncogenic activities suggesting that eIF4E potentiates an oncogenic HA program. These studies provide unique insights into the mechanisms driving HA production and demonstrate that an oncoprotein can co-opt HA biosynthesis to drive malignancy.

Genetic and pharmacologic inhibition of eIF4E reduces breast cancer cell migration, invasion, and metastasis

The translation initiation factor eIF4E is an oncogene that is commonly overexpressed in primary breast cancers and metastases. In this article, we report that a pharmacologic inhibitor of eIF4E function, ribavirin, safely and potently suppresses breast tumor formation. Ribavirin administration blocked the growth of primary breast tumors in several murine models and reduced the development of lung metastases in an invasive model. Mechanistically, eIF4E silencing or blockade reduced the invasiveness and metastatic capability of breast cancer cells in a manner associated with decreased activity of matrix metalloproteinase (MMP)-3 and MMP-9. Furthermore, eIF4E silencing or ribavirin treatment suppressed features of epithelial-to-mesenchymal transition, a process crucial for metastasis. Our findings offer a preclinical rationale to explore broadening the clinical evaluation of ribavirin, currently being tested in patients with eIF4E-overexpressing leukemia, as a strategy to treat solid tumors such as metastatic breast cancer.

Abstract 3710: The role of eIF4E in promoting melanoma cell proliferation and maintaining acquired resistance to Vemurafenib in melanoma

In eukaryotic cells, mRNA translation is restricted by the translation initiation step, in which eIF4E has been regarded as a master regulator. Overexpression of eIF4E has been found in different cancer types; however, whether eIF4E is involved in melanoma tumorigenesis and resistance to standard of care in melanoma remains unclear. We hypothesize that eIF4E promotes melanoma cell proliferation and facilitates the development of acquired resistance to the B-raf inhibitor, Vemurafenib. From our preliminary data, we show that eIF4E is overexpressed in a panel of malignant melanoma cell lines compared to immortalized melanocytes Mel ST. By genetically knocking down eIF4E via siRNA, we can significantly repress the proliferation of a subset of melanoma cell lines and decrease the level of the eIF4E downstream target Cyclin D1. In addition, the B-raf inhibitor Vemurafenib can drastically inhibit 4EBP-1 phosphorylation in BRAFV600E melanoma cell lines, and further cap binding analysis confirmed that Vemurafenib stabilizes the eIF4E - 4EBP-1 association in these cell lines.. In contrast, 4EBP-1 is highly phosphorylated in all Vemurafenib resistant cell lines, compared to the parental A375, even in the presence of Vemurafenib. Furthermore, cap binding assay show that, unlike their parental counterpart, four out of six resistant lines exhibit weak eIF4E - 4EBP-1 association even in the presence of Vemurafenib. This may imply that more free eIF4E is available for cap-dependent translation initiation in Vemu resistant lines compared to the parental A375. Besides, eIF4E activity contributes to the proliferation of some melanoma cell lines with acquired resistance to Vemurafenib, since siRNA-silencing eIF4E decreases their proliferation. In conclusion, our data show that eIF4E promotes proliferation of some melanoma cell lines and may be involved in maintaining the survival of some melanoma cell lines with acquired vemurafenib resistance. These data suggest that therapeutically targeting eIF4E may be a viable means of inhibiting melanoma cell proliferation and overcoming Vemurafenib resistance.

Citation Format: Yao Zhan, Michael S. Dahabieh, Filippa Pettersson, Monica C. Dobocan, Marie Noel M. Boutchou, Leon Van Kempen, Sonia V. del Rincon, Wilson H. Miller, Jr.. The role of eIF4E in promoting melanoma cell proliferation and maintaining acquired resistance to Vemurafenib in melanoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3710. doi:10.1158/1538-7445.AM2014-3710

Abstract 5538: Development of HDACi resistance in DLBCL leads to a switch in subtype towards a more differentiated B-cell and is associated with increased sensitivity to proteasome inhibition

Diffuse Large B Cell Lymhoma (DLBCL) is a highly heterogeneous disease in terms of clinical presentation, cell morphology, molecular characteristics and response to therapy. Gene expression profiling studies in patients have indicated that DLBCL can be sub-classified in relationship to the different stages of normal B cell development at which the cancer arises; germinal center B cell (GCB) and activated B cell (ABC). More recently, a similar approach distinguished three different reproducible clusters referred to as oxidative phosphorylation (OxPhos), B cell receptor/proliferation (BCR) and host response (HR). Importantly, DLBCL has also been well characterized at the genomic level. A large number of genes encoding epigenetic modifying enzymes are mutated in DLBCL, which implicates epigenetic regulation as an important factor in DLBCL pathogenesis, and a potential target for therapy. Among epigenetic therapies, histone deacetylase inhibitors (HDACi) have shown some clinical activity in DLBCL patients ranging from 5 to 25%, although responsive patients ultimately develop resistance.

Aiming to understand resistance and response to HDACi in DLBCL, we developed HDACi-resistant cell lines from the GCB and BCR subtype cells SUDHL6 and SUDHL4. Gene expression array analysis was performed in parental SUDHL6 and the resistant clone SUDHL6-X. Strikingly, we found that the resistant cells have switched gene expression profile from GCB to ABC subtype and from BCR to OXPHOS. Also, we observe features of more differentiated, plasmablast-like cells in SUDHL6-X cells and in all other resistant subclones we developed, including inactivated B cell receptor signaling, increased endoplasmic reticulum stress and activation of the unfolded protein response. These characteristics are reflected in a distinctive response pattern to other targeted drugs. We observe that HDACi-resistant cells become cross-resistant to the anti-CD20 antibody rituximab, but, interestingly, they gain susceptibility to inhibitors of the proteasome bortezomib and MLN2238. Importantly, analysis of lymphoma cells isolated from de novo resistant DLBCL patients treated with the HDACi panobinostat for 15 days showed a switch in gene expression profiles from GCB to ABC, similar to SUDHL6X cells, indicating that our observations are not exclusive of in vitro systems. In conclusion, we have shown for the first time that resistance to HDACi is associated with differentiation of lymphoma cells that we predict makes them insensitive to drugs targeting the B cell receptor and anti-CD20 antibody, but sensitive to proteasome inhibition.

Citation Format: Daphné Dupéré-Richer, Mena Kinal, Filippa Pettersson, Mona Hassawi, Yang ShaoNing, Torsten H. Nielsen, Kathleen Klein, Teresa Ezponda-Itoiz, Jonathan D. Licht, Nathalie Johnson, Sarit E. Assouline, Leandro Cerchietti, Wilson H. Miller, Koren K. Mann. Development of HDACi resistance in DLBCL leads to a switch in subtype towards a more differentiated B-cell and is associated with increased sensitivity to proteasome inhibition. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5538. doi:10.1158/1538-7445.AM2014-5538

Expression of leukemia-associated fusion proteins increases sensitivity to histone deacetylase inhibitor-induced DNA damage and apoptosis

Histone deacetylase inhibitors (HDI) show activity in a broad range of hematologic and solid malignancies, yet the percentage of patients in any given malignancy who experience a meaningful clinical response remains small. In this study, we sought to investigate HDI efficacy in acute myeloid leukemia (AML) cells expressing leukemia-associated fusion proteins (LAFP). HDIs have been shown to induce apoptosis, in part, through accumulation of DNA damage and inhibition of DNA repair. LAFPs have been correlated with a DNA repair-deficient phenotype, which may make them more sensitive to HDI-induced DNA damage. We found that expression of the LAFPs PLZF-RARα, PML-RARα, and RUNX1-ETO (AML1-ETO) increased sensitivity to DNA damage and apoptosis induced by the HDI vorinostat. The increase in apoptosis correlated with an enhanced downregulation of the prosurvival protein BCL2. Vorinostat also induced expression of the cell-cycle regulators p19(INK4D) and p21(WAF1) and triggered a G2-M cell cycle arrest to a greater extent in LAFP-expressing cells. The combination of LAFP and vorinostat further led to a greater downregulation of several base excision repair (BER) enzymes. These BER genes represent biomarker candidates for response to HDI-induced DNA damage. Notably, repair of vorinostat-induced DNA double-strand breaks was found to be impaired in PLZF-RARα-expressing cells, suggesting a mechanism by which LAFP expression and HDI treatment cooperate to cause an accumulation of damaged DNA. These data support the continued study of HDI-based treatment regimens in LAFP-positive AMLs.

Vorinostat-induced autophagy switches from a death-promoting to a cytoprotective signal to drive acquired resistance

Histone deacetylase inhibitors (HDACi) have shown promising activity against hematological malignancies in clinical trials and have led to the approval of vorinostat for the treatment of cutaneous T-cell lymphoma. However, de novo or acquired resistance to HDACi therapy is inevitable, and their molecular mechanisms are still unclear. To gain insight into HDACi resistance, we developed vorinostat-resistant clones from the hematological cell lines U937 and SUDHL6. Although cross-resistant to some but not all HDACi, the resistant cell lines exhibit dramatically increased sensitivity toward chloroquine, an inhibitor of autophagy. Consistent with this, resistant cells growing in vorinostat show increased autophagy. Inhibition of autophagy in vorinostat-resistant U937 cells by knockdown of Beclin-1 or Lamp-2 (lysosome-associated membrane protein 2) restores sensitivity to vorinostat. Interestingly, autophagy is also activated in parental U937 cells by de novo treatment with vorinostat. However, in contrast to the resistant cells, inhibition of autophagy decreases sensitivity to vorinostat. These results indicate that autophagy can switch from a proapoptotic signal to a prosurvival function driving acquired resistance. Moreover, inducers of autophagy (such as mammalian target of rapamycin inhibitors) synergize with vorinostat to induce cell death in parental cells, whereas the resistant cells remain insensitive. These data highlight the complexity of the design of combination strategies using modulators of autophagy and HDACi for the treatment of hematological malignancies.

Abstract 4707: Inhibition of autophagy overcomes acquired resistance to vorinostat

Histone deacetylase inhibitors (HDACi) have recently emerged as promising anticancer agents. Two HDACi, vorinostat (Zolinza®) and romidepsin (Istodax®), are currently FDA approved for use in cutaneous T-cell lymphoma and several others have advanced into Phase II and III clinical trials, both as single agents and in combination with cytotoxics, for a variety of malignancies. Encouraging results have been obtained in haematological malignancies. However, HDACi target many pathways and the full mechanism responsible for their anti-neoplastic activity is still far from clear. An understanding of the molecular mechanisms underlying resistance to HDACi may help to elucidate their mechanism of action and may be of relevance in an attempt to design more effective combination strategies. The purpose of this study is to understand the molecular alterations associated with resistance to vorinostat (Zolinza®). A vorinostat resistant clone (U937-VR) was derived from U937, a monocytic-like histiocytic lymphoma cell line, using a dose escalation protocol. Vorinostat-resistant cells (U937-VR) are able to grow in 2 µM vorinostat without induction of apoptosis. U937-VR cells are cross-resistant to the cytotoxic effects of similar HDACi's such as LBH589, but not to the structurally different benzamide MGCD0103, as measured by propidium iodide (PI) staining and caspase 3/7 activation. Also, resistance demonstrates a partial reversibility that could be indicative of a non-mutational mechanism of resistance. The LD50 of different chemotherapeutic drugs was evaluated by measuring apoptosis with PI staining. U937 parental and U937-VR cells have equivalent LD50 for the DNA damaging agent cisplatin and for the microtubule stabilizing agent taxol, indicating that the apoptotic machinery is intact in U937-VR cells. Interestingly, the resistant cells exhibit increased sensitivity toward chloroquine, an inhibitor of autophagy and to the proteasome inhibitors MG132 and bortezomib. This increased sensitivity correlates with an elevated accumulation of ubiquitinated proteins in U937-VR. These cells also have increased autophagic flux which can be inhibited by knock down of Beclin-1 or Lamp-2, which ultimately restores sensitivity to vorinostat. Autophagy is also activated in parental U937 cells upon treatment with vorinostat, however, in contrast to the resistant cells, its inhibition decreases sensitivity to vorinostat. We therefore propose that autophagy switches from a proapoptotic to a prosurvival signal through chronic exposure to vorinostat. The key players involved in that switch remain to be defined. These data are of importance in the design of combination strategies using inhibitors of autophagy and HDACi for the treatment of hematological malignancies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4707. doi:1538-7445.AM2012-4707

Vorinostat induces reactive oxygen species and DNA damage in acute myeloid leukemia cells

Histone deacetylase inhibitors (HDACi) are promising anti-cancer agents, however, their mechanisms of action remain unclear. In acute myeloid leukemia (AML) cells, HDACi have been reported to arrest growth and induce apoptosis. In this study, we elucidate details of the DNA damage induced by the HDACi vorinostat in AML cells. At clinically relevant concentrations, vorinostat induces double-strand breaks and oxidative DNA damage in AML cell lines. Additionally, AML patient blasts treated with vorinostat display increased DNA damage, followed by an increase in caspase-3/7 activity and a reduction in cell viability. Vorinostat-induced DNA damage is followed by a G2-M arrest and eventually apoptosis. We found that pre-treatment with the antioxidant N-acetyl cysteine (NAC) reduces vorinostat-induced DNA double strand breaks, G2-M arrest and apoptosis. These data implicate DNA damage as an important mechanism in vorinostat-induced growth arrest and apoptosis in both AML cell lines and patient-derived blasts. This supports the continued study and development of vorinostat in AMLs that may be sensitive to DNA-damaging agents and as a combination therapy with ionizing radiation and/or other DNA damaging agents.

Abstract 2136: Expression of fusion proteins in acute myeloid leukemia cells increases sensitivity to histone deacetylase inhibitors

Acute myeloid leukemias (AMLs) are often characterized by chromosomal translocations resulting in the expression of fusion proteins (FP). Some FP have been demonstrated to recruit histone deacetylases (HDACs) and repress the expression of DNA repair genes. This may result in an increased sensitivity to histone deacetylase inhibitors (HDI) due to their ability to also down-regulate DNA repair gene expression and induce DNA damage. We have tested the sensitivity of PLZF-RARα, PML-RARα and AML1-ETO inducible cell lines to HDI in order to characterize changes in the mechanisms of cell death.

Treatment of U937 cells with vorinostat results in DNA damage as measured by the COMET assay, followed by cell death. To test the effect of FP expression, U937 cells stably transfected with PLZF-RARα, PML-RARα or AML1-ETO cDNA under the control of a tetracycline-off or a zinc-inducible system were treated with vorinostat and assayed for cell death in the presence/absence of FP. FP expression resulted in increased cell death and caspase-3/7 activation. This effect was found to be largely caspase driven as pre-treatment with the pan-caspase inhibitor Z-VAD-FMK resulted in protection against vorinostat-induced cell death. In addition, FP expressing cells were also exposed to the DNA-targeting agents Doxorubicin, Etoposide, Cisplatin and ionizing radiation. Again, FP expression resulted in increased cell death.

In addition, we investigated the effect of FP expression on vorinostat sensitivity using a PLZF-RARα murine hematopoietic model. A retroviral expression system was used to overexpress PLZF-RARα in lineage-depleted (Lin-) murine hematopoietic progenitors, followed by vorinostat treatment in the absence/presence of PLZF-RARα. The increased sensitivity of FP expressing cells to HDI and DNA-targeting agents suggests a mechanism where the combination of an FP expression and HDI results in an increased accumulation of DNA damage, leading to enhanced cell death.

These findings are significant as they point to FP expressing AMLs as a target group that may respond better to HDI-based therapies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2136. doi:10.1158/1538-7445.AM2011-2136

Ribavirin treatment effects on breast cancers overexpressing eIF4E, a biomarker with prognostic specificity for luminal B-type breast cancer

PURPOSE

We have evaluated the eukaryotic translation initiation factor 4E (eIF4E) as a potential biomarker and therapeutic target in breast cancer. eIF4E facilitates nuclear export and translation of specific, growth-stimulatory mRNAs and is frequently overexpressed in cancer.

EXPERIMENTAL DESIGN

Breast cancer cells were treated with ribavirin, an inhibitor of eIF4E, and effects on cell proliferation and on known mRNA targets of eIF4E were determined. eIF4E expression was assessed, at the mRNA and protein level, in breast cancer cell lines and in skin biopsies from patients with metastatic disease. Additionally, pooled microarray data from 621 adjuvant untreated, node-negative breast cancers were analyzed for eIF4E expression levels and correlation with distant metastasis-free survival (DMFS), overall and within each intrinsic breast cancer subtype.

RESULTS

At clinically relevant concentrations, ribavirin reduced cell proliferation and suppressed clonogenic potential, correlating with reduced mRNA export and protein expression of important eIF4E targets. This effect was suppressed by knockdown of eIF4E. Although eIF4E expression is elevated in all breast cancer cell lines, variability in ribavirin responsiveness was observed, indicating that other factors contribute to an eIF4E-dependent phenotype. Assessment of the prognostic value of high eIF4E mRNA in patient tumors found that significant discrimination between good and poor outcome groups was observed only in luminal B cases, suggesting that a specific molecular profile may predict response to eIF4E-targeted therapy.

CONCLUSIONS

Inhibition of eIF4E is a potential breast cancer therapeutic strategy that may be especially promising against specific molecular subtypes and in metastatic as well as primary tumors.

Abstract 3165: Anti-tumor activity of the eIF4E-targeted drug ribavirin in breast cancer cells

In this study, we explored the potential of targeting the eukaryotic translation initiation factor (eIF4E) with ribavirin as a novel anti-tumor agent in breast cancer. eIF4E is an oncogene that facilitates nuclear export and translation of specific, growth-stimulatory mRNAs, including cyclins, c-myc, survivin, VEGF and others, thereby promoting cell survival. Overexpression of eIF4E also leads indirectly to activation of Akt, providing a positive feed-back loop for eIF4E activation and Akt signaling effects. Ribavirin is an antiviral drug that has been shown to inhibit oncogenic transformation mediated by eIF4E and reduce the clonogenic potential of cancer cells with high eIF4E levels. Ribavirin specifically inhibits translation and/or nuclear export of eIF4E targets in cells both in vitro and in patients, as shown in a recent phase I/II proof-of-principle trial in patients with AML. In this trial, dramatic clinical improvements were observed and reductions in eIF4E levels and activity correlated with clinical response. Importantly, ribavirin is largely non-toxic even at high doses, possibly due to an eIF4E oncogene addiction specific to tumor cells.

eIF4E is overexpressed in more than 50% of breast cancers, and high levels are associated with increased angiogenesis, clinical progression and poor prognosis. Targeting eIF4E with ribavirin may therefore be an attractive therapeutic strategy for this malignancy. We studied the effects of ribavirin in a panel of breast cancer cells, representing luminal and basal-type tumors with various ER, PR and Her2 status. Western blot analysis showed that eIF4E was overexpressed compared to normal breast tissue and predominantly cytoplasmic in all of the cell lines. In addition, we examined eIF4E levels in metastatic skin lesions of three breast cancer patients and found highly elevated levels compared to normal skin. Ribavirin anti-proliferative activity was assessed using a cell viability assay and clonogenic assays were performed to examine changes in both anchorage dependent and -independent growth. At clinically relevant concentrations, the majority of the cell lines responded to ribavirin, with varying sensitivity. Inhibition of cell growth was associated with decreased protein levels of eIF4E targets such as cyclin D1 and survivin, and a reduction in phosphorylation of Akt as well as eIF4E binding protein 1 (4E-BP1) were observed. Cell cycle analysis showed that ribavirin caused a significant S-phase arrest in sensitive cells, while apoptosis was only observed at elevated concentrations of the drug.

This data encourages further study of ribavirin as a breast cancer therapeutic and identification of potential combination regimens. A clinical trial of single agent ribavirin in patients with advanced metastatic breast cancer is planned in the near future.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3165.

Abstract A189: Expression of fusion proteins in acute myeloid leukemia cells increases sensitivity to histone deacetylase inhibitors

Acute Myeloid Leukemias (AMLs) are often characterized by chromosomal rearrangements that result in fusion proteins with aberrant transcriptional regulatory activities. These fusion proteins bind to gene promoters and recruit corepressors such as histone deacetylases (HDACs), which remodel chromatin into a closed conformation thereby silencing genes and contributing to a malignant phenotype. Aberrantly silenced genes include tumor suppressor and pro-differentiation genes. In addition, multiple groups have reported a DNA repair deficient phenotype concurrent with the expression of different fusion proteins in leukemia.

Small molecule HDAC inhibitors (HDACi) were devised as a strategy to reverse transcriptional repression. Indeed, many studies have demonstrated the ability of HDACi to re-sensitize leukemic cells to differentiating stimuli. However, other studies have revealed alternate methods by which HDACi exert anti-tumor activity, including induction of apoptosis that may be dependent on induction of ROS, MAPK signaling etc.

We find that low doses of HDACi, including Vorinostat and LBH589, induce cell death in the AML cell line U937 in a dose and time-dependant manner. Further, Vorinostat induced cell death in U937 cells is preceded by DNA damage and a G2/M arrest. This correlates with reports that HDACi repress DNA repair, by down-regulating DNA repair genes and by acetylating repair proteins thereby impairing their repair function.

Due to the inhibitory effect of leukemic fusion proteins on DNA repair, we predicted that DNA damage induced by HDACi, and thus cell death, would be amplified in AML cells expressing PML-RARα and PLZF-RARα fusion proteins. Sensitivity to Vorinostat and LBH589 was tested in three U937 derived cell lines: PR9 (PML-RARα inducible), B412 (PLZF-RARα inducible) and SN4 (mock transfected control). Indeed, induction of PLZF-RARα increased sensitivity of B412 cells to both Vorinostat- and LBH-mediated cell death. Assaying for DNA damage using alkaline comet assay, PR9 and B412 cells displayed an increase in DNA damage when their respective fusion protein is expressed. Nonetheless, the contribution of DNA damage to HDACi-mediated cell death remains unclear and further study is necessary. These findings are significant as they point to fusion protein expressing AMLs as a target group that may respond better to HDACi-based therapies.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A189.

Abstract A188: Proapoptotic versus prosurvival function of the MAP kinase p38 induced by HDAC inhibitor in hematological malignant cells

Histone deacetylase inhibitors (HDACi) have recently emerged as promising anticancer agents. However, the mechanisms by which HDAC inhibitors arrest proliferation and induce apoptosis in tumor cells is far from clear. Activation of the stress MAP kinases and induction of DNA damage by different HDACi have been reported, however, the potential role of the MAP kinase p38 in the antitumor activity of these drugs has not been described. P38 is known to be activated independently or downstream of DNA damage. The purpose of this study was to elucidate the mechanisms by which the HDACi vorinostat (Zolinza®) triggers apoptosis in haematological malignant cells.

We show that DNA damage as well as activation of p38 occurs relatively early in acute myeloid leukemia (AML) cell lines after treatment with vorinostat. Using comet assays, we detected direct evidence of early DNA damage and western blotting revealed induction of the DNA damage response proteins ATM and Chk2. We performed cell cycle analysis, and observed within the vorinostat-treated AML cell population, cells exiting G1 and accumulating in the G2-M phase of the cell cycle, where they subsequently underwent apoptosis. Notably, downregulation of p38 by shRNA or inhibition of p38 and β activity by the inhibitor SB203580 significantly decreased both G2-M accumulation and apoptosis induced by vorinostat, indicating a pro-apoptotic p38 function.

Interestingly, several other HDACi tested all induced p38 activation but, depending on the HDACi, this activation was found to be either pro or antiapoptotic. The short-chain fatty acid sodium butyrate (NaB) requires p38 for induction of apoptosis, like vorinostat. On the other hand, LBH589, from the structural class encompassing vorinostat, does not depend on p38 for induction of apoptosis. Furthermore, p38 serves as a pro-survival signal when induced by the benzimide MGCD0103.

In conclusion, we have shown that vorinostat-induced apoptosis in AML cells is preceded by generation of DNA damage and accumulation of cells in the G2-M phase of the cell cycle. Further, G2-M arrest and apoptosis induction (but not DNA damage) by vorinostat requires activation of the p38 MAP kinase, which is not the case for all HDACi. Therefore, a better understanding of the role of p38 MAPK in the action of specific HDACi may help in the development of rational combination regimes including these targeted agents.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A188.

Inhibition of DNA methyltransferase activates tumor necrosis factor alpha-induced monocytic differentiation in acute myeloid leukemia cells

Transcriptional silencing via promoter methylation of genes important for cell growth and differentiation plays a key role in myeloid leukemogenesis. We find that clinically achievable levels of 5-aza-2'-deoxycytidine (5-AZA-dC), a potent inhibitor of DNA methylation, can modify chromatin and restore the ability of tumor necrosis factor alpha (TNFalpha) to induce monocytic differentiation of the acute myeloid leukemia cells NB4 and U937. Although 5-AZA-dC cannot fully induce differentiation, we show that 5-AZA-dC acts directly on TNFalpha-responsive promoters to facilitate TNFalpha-induced transcriptional pathways leading to differentiation. 5-AZA-dC regulates the expression of Dif-2, a TNFalpha target gene, by deacetylating chromatin domains in a methylation-dependent manner. Chromatin immunoprecipitation analyses of the Dif-2 promoter show histone hyperacetylation and a recruitment of the nuclear factor-kappaB transcription factor in response to 5-AZA-dC. Furthermore, 5-AZA-dC plus TNFalpha enhances the level of phosphorylated RNA Pol II at the Dif-2 promoter via synergistic recruitment of TFIIH. We conclude that nonspecific changes in chromatin can allow a specific transcriptional inducer to overcome blocks in leukemic cell differentiation. Our results support the concept of low doses of 5-AZA-dC acting in combination with other agents to target epigenetic changes that drive malignant growth in leukemic cells. [Cancer Res 2009;69(1):55-64].

Rexinoids modulate steroid and xenobiotic receptor activity by increasing its protein turnover in a calpain-dependent manner

The steroid and xenobiotic receptor SXR (human pregnane X receptor) is a nuclear receptor that plays a key role in the body's detoxification response by regulating genes involved in drug metabolism and transport. SXR ligands include a wide range of compounds, which induce transcription of SXR target genes via activation of a heterodimeric transcription factor consisting of SXR and the related nuclear receptor retinoid X receptor (RXR). We investigated the effect of RXR-selective ligands, rexinoids, on SXR/RXR activity. In agreement with previous reports, we found that rexinoids are weak activators of SXR, but we also found that they can antagonize SXR activation by the potent SXR agonist rifampicin. This antagonism included suppression of rifampicin-induced expression of SXR target genes, as well as reduced binding of SXR/RXR to SXR response elements both in vivo and in vitro. Interestingly, two rexinoids, bexarotene (LGD1069/Targretin) and LG100268, caused a rapid and sustained decrease in the protein levels of both SXR and RXR. The decrease in SXR level was due to an enhanced rate of protein degradation and was dependent on calpain activity, as opposed to rexinoid-induced RXR degradation, which is mediated via the proteasome. Thus, we have demonstrated a novel, rexinoid-modulated mechanism regulating SXR protein stability, which may explain why rexinoids are only weak activators of SXR/RXR-mediated transcription, despite reports that they bind to SXR with high affinity. We suggest that the ability of rexinoids to induce degradation of both SXR and RXR, in combination with competition for binding to SXR, can also explain why rexinoids antagonize the activation of SXR by drugs like rifampicin.

Retinoic acid modulates chromatin to potentiate tumor necrosis factor alpha signaling on the DIF2 promoter

Transcriptional activation by nuclear hormone receptors is well characterized, but their cooperation with other signaling pathways to activate transcription remains poorly understood. Tumor necrosis factor alpha (TNFα) and all-trans retinoic acid (RA) induce monocytic differentiation of acute promyelocytic leukemia (APL) cells in a synergistic manner. We used the promoter of DIF2, a gene involved in monocytic differentiation, to model the mechanism underlying the cooperative induction of target genes by RA and TNFα. We show a functional RA response element in the DIF2 promoter, which is constitutively bound by PML/RARα in APL cells. RA stimulates release of corepressors and recruitment of chromatin modifying proteins and additional transcription factors to the promoter, but these changes cause only a modest induction of DIF2 mRNA. Co-stimulation with RA plus TNFα facilitates binding of NF-κB to the promoter, which is crucial for full induction of transcription. Furthermore, RA plus TNFα greatly enhanced the level of RNA Pol II phosphorylation on the DIF2 promoter, via synergistic recruitment of TFIIH. We propose that RA mediates remodeling of chromatin to facilitate binding of transcription factors, which cooperate to enhance Pol II phosphorylation, providing a mechanism whereby nuclear receptors interact with other signaling pathways on the level of transcription.

Protein expression in experimental malignant glioma varies over time and is altered by radiotherapy treatment

Radiotherapy is one of the mainstays of glioblastoma (GBM) treatment. This study aims to investigate and characterise differences in protein expression patterns in brain tumour tissue following radiotherapy, in order to gain a more detailed understanding of the biological effects. Rat BT4C glioma cells were implanted into the brain of two groups of 12 BDIX-rats. One group received radiotherapy (12 Gy single fraction). Protein expression in normal and tumour brain tissue, collected at four different time points after irradiation, were analysed using surface enhanced laser desorption/ionisation – time of flight – mass spectrometry (SELDI-TOF-MS). Mass spectrometric data were analysed by principal component analysis (PCA) and partial least squares (PLS). Using these multivariate projection methods we detected differences between tumours and normal tissue, radiation treatment-induced changes and temporal effects. 77 peaks whose intensity significantly changed after radiotherapy were discovered. The prompt changes in the protein expression following irradiation might help elucidate biological events induced by radiation. The combination of SELDI-TOF-MS with PCA and PLS seems to be well suited for studying these changes. In a further perspective these findings may prove to be useful in the development of new GBM treatment approaches.

Enhanced retinoid-induced apoptosis of MDA-MB-231 breast cancer cells by PKC inhibitors involves activation of ERK

Retinoids are vitamin A derivatives, which cause growth inhibition, differentiation and/or apoptosis in various cell types, including some breast cancer cells. In general, estrogen receptor (ER)-positive cells are retinoic acid (RA) sensitive, whereas ER-negative cells are resistant. In this report, we show that ER-negative MDA-MB-231 cells are strongly growth inhibited by retinoids in combination with a PKC inhibitor. While neither RA nor GF109203X (GF) has a significant growth inhibitory effect in these cells, RA+GF potently suppress proliferation. We found that RA+GF induce apoptosis, as shown by an increase in fragmented DNA, Annexin-V-positive cells and caspase-3 activation. Apoptosis was also induced by GF in combination with two synthetic retinoids. Expression of phosphorylated as well as total PKC was decreased by GF and this was potentiated by RA. In addition, treatment with GF caused a strong and sustained activation of ERK1/2 and p38-MAPK, as well as a weaker activation of JNK. Importantly, inhibition of ERK but not p38 or JNK suppressed apoptosis induced by RA+GF, indicating that activation of ERK is specifically required. In support of this novel finding, the ability of other PKC inhibitors to cause apoptosis in combination with RA correlates with ability to cause sustained activation of ERK.

ERβ Sensitizes Breast Cancer Cells to Retinoic Acid: Evidence of Transcriptional Crosstalk

The ability of retinoids to inhibit breast cancer cell growth correlates with estrogen receptor (ER) α status, as shown by the antiproliferative effects of retinoids in ERα-positive breast cancer cells and their use as chemopreventive agents in premenopausal women. The discovery of ERβ, also present in breast cancer cells, has added a new level of complexity to this malignancy. To determine the retinoid response in ERβ-expressing breast cancer cells, we used retroviral transduction of ERβ in ER-negative MDA-MB-231 cells. Western blot and immunofluorescence confirmed expression and nuclear localization of ERβ, whereas functionality was shown using an estrogen response element–containing reporter. A significant retinoic acid (RA)–mediated growth inhibition was observed in the transduced ERβ-positive cells as shown by proliferation assays. Addition of estradiol, tamoxifen, or ICI 182,780 had no effect on cell growth and did not alter RA sensitivity. We observed that retinoids altered ERβ-mediated transcriptional activity from an estrogen response element, which was confirmed by decreased expression of the pS2 gene, and from an activator protein response element. Conversely, the expression of ERβ altered RA receptor (RAR) β expression, resulting in greater induction of RARβ gene expression on RA treatment, without altered expression of RARα. Our data provide evidence of transcriptional crosstalk between ERβ and RAR in ERβ-positive breast cancer cells that are growth inhibited by RA.

ERbeta sensitizes breast cancer cells to retinoic acid: evidence of transcriptional crosstalk

The ability of retinoids to inhibit breast cancer cell growth correlates with estrogen receptor (ER) alpha status, as shown by the antiproliferative effects of retinoids in ERalpha-positive breast cancer cells and their use as chemopreventive agents in premenopausal women. The discovery of ERbeta, also present in breast cancer cells, has added a new level of complexity to this malignancy. To determine the retinoid response in ERbeta-expressing breast cancer cells, we used retroviral transduction of ERbeta in ER-negative MDA-MB-231 cells. Western blot and immunofluorescence confirmed expression and nuclear localization of ERbeta, whereas functionality was shown using an estrogen response element-containing reporter. A significant retinoic acid (RA)-mediated growth inhibition was observed in the transduced ERbeta-positive cells as shown by proliferation assays. Addition of estradiol, tamoxifen, or ICI 182,780 had no effect on cell growth and did not alter RA sensitivity. We observed that retinoids altered ERbeta-mediated transcriptional activity from an estrogen response element, which was confirmed by decreased expression of the pS2 gene, and from an activator protein response element. Conversely, the expression of ERbeta altered RA receptor (RAR) beta expression, resulting in greater induction of RARbeta gene expression on RA treatment, without altered expression of RARalpha. Our data provide evidence of transcriptional crosstalk between ERbeta and RAR in ERbeta-positive breast cancer cells that are growth inhibited by RA.

Primary carcinoma of the vagina: factors influencing the age at diagnosis. The Radiumhemmet series 1956-96

The objective to this retrospective study of 341 cases of primary carcinoma of vagina (PCV) diagnosed between 1956 and 1996 was to find whether epidemiological, clinical, and histopathological variables were related to the age at diagnosis of patients with PCV. The univariate statistical analysis showed that younger age at diagnosis significantly correlated with a history of cervical dysplasia, hysterectomy, gynecological infections, and tumors located in the upper part of the vagina, whereas older age at diagnosis significantly correlated with late menarche and exophytically growing tumors. In the multivariate regression analysis, the remaining independent predictors were a history of cervical dysplasia and age at menarche. Further, parity >/=4 as well as nulliparity, smoking, and unstable marital status were more common among patients with PCV than among those in the general Swedish female population. This study indicates that the etiology of vaginal carcinoma may be age related. In young patients, the disease seems to be etiologically related to cervical neoplasia and thus human papillomavirus (HPV) dependent. However, in the most common age group, the older patients, there might be another (probably non-HPV-related) etiology associated with hormonal factors and trauma to the vagina.

The N-terminal of the estrogen receptor (ERalpha) mediates transcriptional cross-talk with the retinoic acid receptor in human breast cancer cells

Transcriptional cross-talk exists between the estrogen receptor (ERalpha) and retinoic acid receptor (RAR) pathways in human breast cancer cells. We have previously shown that re-expression of ERalpha in ER-negative cells stimulates the transcriptional and growth inhibitory effects of all-trans-retinoic acid (tRA) by a mechanism that is independent of the ER ligands estradiol and tamoxifen. In this study, we generated cell lines stably expressing ERalpha-deletion mutants to elucidate the mechanism whereby ERalpha modulates RAR transcriptional activity. Using RT-PCR and RNAse protection assays, we observed that expression of ERalpha suppresses basal expression of the RA-responsive gene RARbeta2, while allowing it to be strongly induced by tRA. Repression of basal RARbeta2 transcription was confirmed by transient expression of the reporter plasmid betaRE-tk-CAT, containing the RARbeta2 promoter. In the ERalpha-negative cells, on the other hand, transcription was only weakly induced by RA. We further determined that this effect of ERalpha on RARbeta induction required the N-terminal AF-1-containing region, including the DNA-binding domain, but was independent of the C-terminal ligand-binding domain. Consistent with these results, the ER agonist estradiol and the AF-2 antagonist 4-hydroxytamoxifen had no significant effect on betaRARE activity. Conversely, the full ER antagonist ICI 182,780, which blocks ERalpha AF-1 activity, was able to completely relieve repression of basal betaRARE activity. The effect of ERalpha is specific for RAR-mediated transcription and does not occur on promoters containing typical response elements for the Vitamin D or thyroid hormone receptors. Moreover, the cross-talk between ERalpha and RAR does not seem to be mediated by sequestration of a number of common co-regulators, suggesting a novel mechanism whereby the N-terminal region of ERalpha modulates the transcriptional activity of RAR.

Retinoids cause apoptosis in pancreatic cancer cells via activation of RAR-gamma and altered expression of Bcl-2/Bax

All-trans-retinoic acid and 9-cis-retinoic acid have been reported to have inhibitory effects on pancreatic adenocarcinoma cells and we have shown that this is partly due to induction of apoptosis. In this study, the mechanisms whereby 9-cis-retinoic acid induces apoptosis in these cells were investigated. An involvement of the Bcl-2 family of proteins was shown, such that 9-cis-retinoic acid causes a decrease in the Bcl-2/Bax ratio. Overexpression of Bcl-2 also resulted in inhibition of apoptosis induced by 9-cis-retinoic acid. Furthermore, two broad-range caspase inhibitors blocked DNA fragmentation induced by 9-cis-retinoic acid, but had no effect on viability defined by mitochondrial activity. Using synthetic retinoids, which bind selectively to specific retinoic acid receptor subtypes, we further established that activation of retinoic acid receptor-gamma is essential for induction of apoptosis. Only pan-retinoic acid receptor and retinoic acid receptor-gamma selective agonists reduced viability and a cell line expressing very low levels of retinoic acid receptor-gamma is resistant to the effects of 9-cis-retinoic acid. A retinoic acid receptor-beta/gamma selective antagonist also suppressed the cytotoxic effects of 9-cis-retinoic acid in a dose-dependent manner. This study provides important insight into the mechanisms involved in suppression of pancreatic tumour cell growth by retinoids. Our results encourage further work evaluating the clinical use of receptor subtype selective retinoids in pancreatic carcinoma.

Retinoic acid enhances the cytotoxic effects of gemcitabine and cisplatin in pancreatic adenocarcinoma cells

INTRODUCTION

Retinoids, which are derivatives of vitamin A, are important factors involved in the control of biologic functions such as cell growth and differentiation, development, and carcinogenesis. We have shown previously that the naturally occurring retinoids all-trans-retinoic acid (ATRA) and 9-cisretinoic acid (9cRA) induce growth inhibition followed by apoptosis in pancreatic adenocarcinoma cells in vitro.

AIM

To evaluate the efficacy of retinoids in combination with the chemotherapeutic drugs gemcitabine and cisplatin.

METHODOLOGY

In vitro growth inhibition and induction of apoptosis by different combinations of retinoids and cytotoxic drugs were studied by using the T3M-4 and BxPc-3 cell lines. For in vivo studies, T3M-4 cells were injected subcutaneously in nude mice.

RESULTS

Pre-treatment of pancreatic adenocarcinoma cells with ATRA or 9cRA before the addition of the drugs resulted in significant reduction in cell number compared with treatment with the drugs alone. Pre-treatment with 9cRA followed by gemcitabine or cisplatin alone also resulted in a strong increase in the percentage of cells undergoing programmed cell death, or apoptosis. Furthermore, there was an indication that the combination of ATRA and gemcitabine caused increased apoptosis in vivo.

CONCLUSION

Our results clearly suggest the need for additional studies exploring the potential role of the combination of retinoids and gemcitabine in the management of pancreatic cancer.

Fresh isolates from children with severe Plasmodium falciparum malaria bind to multiple receptors

The sequestration of Plasmodium falciparum-infected erythrocytes (pRBC) away from the peripheral circulation is a property of all field isolates. Here we have examined the pRBC of 111 fresh clinical isolates from children with malaria for a number of adhesive features in order to study their possible coexpression and association with severity of disease. A large number of adhesion assays were performed studying rosetting, giant rosetting, and binding to CD36, intercellular adhesion molecule 1, platelet endothelial cell adhesion molecule 1, thrombospondin, heparin, blood group A, and immunoglobulins. Suspension assays were performed at the actual parasitemia of the isolate, while all the static adhesion assays were carried out at an equal adjusted parasitemia. The ability to bind to multiple receptors, as well as the ability to form rosettes and giant rosettes, was found to be more frequent among isolates from children with severe versus mild malaria (P = 0.0015). Rosettes and giant rosettes were more frequent for children with severe malaria, and the cell aggregates were larger and tighter, than for those with mild disease (P = 0.0023). Binding of immunoglobulins (97% of isolates) and of heparin (81% of isolates) to infected erythrocytes was common, and binding to heparin and blood group A was associated with severity of disease (P = 0.011 and P = 0.031, respectively). These results support the idea that isolates that bind to multiple receptors are involved in the causation of severe malaria and that several receptor-ligand interactions work synergistically in bringing about severe disease.

Carcinoma of the cervical stump. The radiumhemmet series 1959-1987. Treatment and prognosis

BACKGROUND

The purpose of this retrospective study is to evaluate the longterm prognosis for cervical stump cancer compared to matched controls with cancer in an intact uterus.

METHODS

From 1959 to 1987, 145 patients were treated for an infiltrating carcinoma of the cervical stump at Radiumhemmet representing 2.2% of all cervical cancers. Three control cases to each case were selected from the cohort of cervical carcinoma cases - matched to year of treatment, stage, histology and age (plus, minus 2 years). Actuarial survival was calculated for cases and controls. Survival differences were analyzed with the Kaplan-Meier technique. The age distribution for cases ranged between 36 and 84 years with a mean age of 60.6 years. The mean age for the control series is 9 years of age (range 35-86 years). Among the cases 87.6% were squamous cell carcinoma and 12.4% were adenocarcinomas. Treatment of carcinoma of the uterine stump at Radiumhemmet followed the same modality as was practised for ordinary cervical cancer cases i.e. two brachyradium applications with 3 weeks interval followed by external irradiation. The dose of irradiation from the intracavitary application given to the stump cancers was lower than that given to comparable cases of the common cervical cases.

RESULTS

No evidence was found of poorer longterm prognosis for radiologically treated squamous cell carcinoma of the uterine stump compared to that of the ordinary cervical carcinomas. Stump cancers of the adenocarcinoma type had a worse prognosis than adenocarcinomas in an intact uterus (p<0.07) and also compared with stump cancers of the squamous epithelial type (p=0.05). The complication rate was higher for the stump cancer cases compared with that for cervical cancers in intact uterus. The mean time interval from subtotal hysterectomy to the stump cancer diagnosis was 17.6 years with a range from 1 to 46 years.

CONCLUSIONS

Recent discussions argue for a better sexual function after subtotal hysterectomy. Our study gave no convincing argument in terms of poorer prognosis for radiologically treated carcinoma of the uterine stump compared to that of the total cervical cancer series. It is thus necessary to weigh the possible gains with subtotal hysterectomy against the relatively low risk to fall victim of a stump cancer. Complications following surgery, as well as possible physiologic and sexual functions of the cervix, should be taken into account.

Differential and antagonistic effects of 9-cis-retinoic acid and vitamin D analogues on pancreatic cancer cells in vitro

Retinoids and vitamin D are known to exert important anti-tumour effects in a variety of cell types. In this study the effects of 9-cis-retinoic acid (9cRA) the vitamin D analogues EB1089 and CB1093 on three pancreatic adenocarcinoma cell lines were investigated. All compounds caused inhibition of in vitro growth but the vitamin D analogues were generally the more potent growth inhibitors. They were also more effective on their own than in combination with 9cRA. Growth arrest correlated with an increased proportion of cells in the G0/G1 phase. Apoptosis was induced in the three cell lines by 9cRA, whereas neither EB1089 nor CB1093 had this effect. Furthermore, addition of EB1089 or CB1093 together with 9cRA resulted in significantly reduced apoptosis. Our results show that retinoic acids as well as vitamin D analogues have inhibitory effects on pancreatic tumour cells but different and antagonistic mechanisms seem to be employed.

Malignant mixed müllerian tumors of the ovary: histopathologic and clinical review of 36 cases

Among 2,895 malignant ovarian tumor cases referred to Radiumhemmet, Stockholm from 1975 through 1995, 36 were certified to be malignant mixed müllerian tumors. The overall prognosis was poor with only 18% five-year actuarial survival (median survival 16.6 months). Five patients are still surviving after 75, 68, 117, 121, and 168 months, respectively. Fifteen women treated with melphelan, doxorubicin (adriamycin) and cisplatin (MAP) had a five-year actuarial survival of 33.3% and a median survival of 19.8 months. In a multivariate analysis taking into account stage, age, radiation, type of chemotherapy, histopathologic type and completeness of surgery, the most important predictors for survival were stage (stages I-II vs stages III-IV, P < 0.05), histopathologic type (homologous vs heterologous, P < 0.05), and type of chemotherapy (MAP or CAP vs other types, P < 0.05). We concluded that homologous tumor and chemotherapy containing cisplatin, doxorubicin, and melphalan, as well as early stage of the tumor, provided the optimal survival rate.

Delay in diagnosis of epithelial ovarian cancer

OBJECTIVES

To investigate and analyze the process from first recognition of symptom(s) to final diagnosis at operation in patients with ovarian epithelial cancer.

METHOD

The medical records of 160 women with ovarian cancer were studied and traced back to the doctor first consulted, in order to obtain information on patient- and doctor-related delay.

RESULTS

Symptom duration was 12 weeks in patients with serous tumors and 7 weeks in patients with other histopathological classes; 56% were diagnosed within 4 weeks. Women in stages I and II were diagnosed faster than those in stages III and IV; 4% were diagnosed within 3 days because of an emergency operation; 30% were not diagnosed within 8 weeks.

CONCLUSION

Diagnosis of ovarian cancer is difficult due to the vagueness of the symptoms which mislead both patients and doctors. Methods to enable earlier diagnosis must be sought.

Bladder tumours following chemotherapy and radiotherapy for ovarian cancer: a case-control study

A collaborative group of cancer registries and hospitals carried out a case-control study of tumours of the bladder in women who had previously been treated for ovarian cancer. A total of 63 cases of bladder tumours were identified, and 188 controls were selected matching for age, year of ovarian cancer diagnosis and survival time. Full details of the treatment for ovarian cancer were sought for both cases and for controls. The risk of bladder tumours was increased for patients who had been treated by radiotherapy alone (1.9; 95% confidence interval, 0.77-4.9), by chemotherapy alone (3.2; 0.97-10), and by chemotherapy and radiotherapy (5.2; 1.6-16), when comparison was made with patients treated only by surgery. Patients treated by chemotherapy were separated into 2 groups according to whether they had received cyclophosphamide. Among those who had, there was a clear increase in risk (approximately 4-fold) regardless of whether or not they had also received radiotherapy. For those who received only other drugs, risk was increased substantially among patients who had also been treated by radiation, as compared with patients treated by surgery alone, and those who had received radiotherapy only. Both melphalan and thiotepa were implicated as potential bladder carcinogens on the basis of these results. The estimated risk of bladder tumours due to cyclophosphamide was more than twice the risk following radiation to the bladder, and it appeared substantially earlier. For both agents, the risk continued to increase more than 10 years after treatment began.