Abstract 1911: A common BIM polymorphism mediates intrinsic resistance and inferior responses to tyrosine kinase inhibitors in cancer

The use of tyrosine kinase inhibitors (TKI) to target oncogenic kinases has led to remarkable responses in patients with chronic myeloid leukemia (CML) and EGFR-mutated non-small cell lung cancer (EGFR NSCLC). However, a significant subset of patients have a minimal or very brief response. It has been suggested that germline polymorphisms may account for this upfront TKI resistance, and that identifying such polymorphisms will allow personalization of targeted therapy to achieve optimal responses in patients. Using paired-end DNA sequencing, we discovered a common (12.3% carrier rate) deletion polymorphism in intron 2 of the BIM gene. BIM is a pro-apoptotic member of the BCL2 family of proteins, and is required for TKIs to induce apoptosis in many cancers. We investigated the effects of the polymorphism on BIM function and TKI resistance in CML and EGFR NSCLC. Inspection of BIM gene structure suggested the polymorphism would result in mutually exclusive splicing of exon 3 (E3) and 4 (E4). Importantly, such an event is predicted to affect TKI sensitivity, since the pro-apoptotic BH3 domain is found only in E4. Using minigenes, we confirmed the deletion favored splicing of E3 over E4 by 5-fold (p=0.008), and that the deletion contained a cis-acting splicing suppressor. Next, using Zn finger nuclease-editing, we recreated the polymorphism in TKI sensitive CML (K562) and EGFR NSCLC (PC9) cell lines. Polymorphism-containing subclones had increased E3/E4 transcript ratios, decreased expression of BH3-containing BIM protein and defective apoptotic signaling, and were intrinsically TKI resistant. Importantly, while manipulation of E3-containing transcript levels did not alter the resistance phenotype, pharmacologic restoration of BH3 function (using a BH3 mimetic ABT-737) restored apoptotic signaling as well as TKI-sensitivity. Finally, we determined if the polymorphism predicted for inferior clinical responses in TKI-treated CML and EGFR NSCLC patients. In 203 CML patients, the polymorphism predicted inferior imatinib responses (defined by EuropeanLeukemiaNet criteria) among those with the polymorphism vs those without (odds ratio=2.94, p=0.02, 95% CI 1.17-7.43). In 141 EGFR NSCLC patients, the polymorphism predicted a shorter PFS of 6.6 vs 11.9 months (p=0.0027), and was independently prognostic for poorer PFS (hazard ratio=2.14, p=0.0026, 95% CI 1.30-3.50). In summary, by altering BIM splicing, the BIM polymorphism is sufficient to cause intrinsic TKI resistance in vitro, and predicts inferior TKI responses in patients. Upfront testing of CML and EGFR NSCLC patients for the BIM polymorphism may identify individuals at risk for developing clinical TKI resistance. Our results also offer an explanation for the heterogeneity of TKI responses among CML and EGFR NSCLC patients, and suggest the possibility of personalizing therapy with BH3 mimetics to improve TKI responses.

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 1911. doi:1538-7445.AM2012-1911

Prevalence and specificity of red-blood-cell antibodies in a multiethnic South and East Asian patient population and influence of using novel MUT+Mur+ kodecytes on its detection

BACKGROUND AND OBJECTIVES

Appropriate screening for irregular red-cell antibodies is essential for ensuring transfusion compatibility and for antenatal management of mothers at risk of haemolytic disease of the foetus and newborn. Screening for all relevant antibodies is, however, limited by screening cells that do not express antigens present in the patient and donor population. Technology to artificially incorporate antigens into red cells is currently available and may be an option for customizing screening cells.

MATERIALS AND METHODS

We sought to identify retrospectively the changing patterns of alloantibody prevalence in our multiethnic population on change of screening cells. Antibody screening records of 143 501 patients tested from 2004 to 2010 were retrieved and divided into two groups: period-1 (2004-2008) and period-2 (2009-2010). During period-1, standard screening cells were used while in period-2, MUT+Mur+ KODE(™) transformed red cells (kodecytes) were used.

RESULTS

Four per cent of samples tested during period-2 were positive on antibody screening compared to 3·2% in period-1. Specific antibodies, excluding anti-D, were identified in 1·66% and 1·52% of patients in period-2 and -1, respectively. When confined to antibodies of clinical significance only, period-2 showed higher alloantibody prevalence of 1·16% as compared to 0·66% in period-1. Antibodies to glycophorin variants of MNS (vMNS) were more commonly detected while antibodies to Lewis antigens declined during period-2.

CONCLUSION

  Antibodies to vMNS antigens are common in South and East Asian populations and are often missed when using standard screening cells. Use of specifically engineered screening cells to express red-cell antigens artificially is beneficial in detecting the diverse alloantibodies present in our population.

Inventory management

A critical aspect of blood transfusion is the timely provision of high quality blood products. This task remains a significant challenge for many blood services and blood systems reflecting the difficulty of balancing the recruitment of sufficient donors, the optimal utilization of the donor's gift, the increasing safety related restrictions on blood donation, a growing menu of specialized blood products and an ever-growing imperative to increase the efficiency of blood product provision from a cost perspective. As our industry now faces questions about our standard practices including whether or not the age of blood has a negative impact on recipients, it is timely to take a look at our collective inventory management practices. This International Forum represents an effort to get a snap shot of inventory management practices around the world, and to understand the range of different products provided for patients. In addition to sharing current inventory management practices, this Forum is intended to foster an exchange of ideas around where we see our field moving with respect to various issues including specialty products, new technologies, and reducing recipient risk from blood transfusion products.

The utility of immature reticulocyte fraction as an indicator of erythropoietic response to altitude training in elite cyclists

Altitude training is sometimes employed by elite endurance athletes to improve their sea level performance. This improvement results from the increased red cell mass consequent upon the boost in erythropoietin (EPO) level that occurs as a response to the relatively hypoxic environment at high altitudes. We measured serum EPO levels together with various red cell and reticulocyte parameters including immature reticulocyte fraction (IRF) in eight national track-endurance cyclists, resident at sea-level, prior to and upon return from an altitude of approximately 1905 m. Reticulocytes and soluble transferrin receptor (sTfR) were significantly increased with reduction in ferritin levels immediately on return from high altitude indicating increased erythropoietic activity. IRF in particular showed a significant peak immediately on return but decline to sub-baseline levels by day 9, and recovery to baseline by day 16. Our results indicate that IRF is a sensitive marker of erythropoietic status in athletes undergoing altitude training and subsequent loss of EPO stimuli on return to sea level.

Chronic neutrophilic leukaemia

Chronic neutrophilic leukaemia is a rare myeloproliferative disease characterised by splenomegaly, sustained neutrophilia, raised vitamin B12 level and absence of the Philadelphia chromosome. We report a 74-year-old man who presented first with Sweet's syndrome and subsequently leukocytosis. He had splenomegaly, a raised vitamin B12 level, serum uric acid and neutrophil alkaline phosphatase score. Cytogenetic study of the marrow was normal and peripheral blood for BCR-ABL gene transcript was not detectable. He subsequently passed away with bronchopneumonia.

Anaemia and iron status among blood donors in a blood transfusion unit in Malaysia

Iron deficiency is a major complication of regular blood donation as a result of regular iron loss from each donated blood unit. Ninety-two regular blood donors and 95 first time blood donors attending a hospital-based blood transfusion centre were assessed as to their haematological and iron status by blood counts and serum ferritin levels as an indicator of iron stores. All donors had passed the haemoglobin-screening test using a copper sulphate method prior to blood donation. Ferritin levels were found to be significantly lower among regular blood donors (47.8 mmol/L) as compared to first time blood donors (94.2 mmol/L). Iron deficiency as observed by low ferritin levels was seen in 7.4% of all first time donors as compared to 17.4% in regular donors. Male first time donors showed a low prevalence of iron deficiency but the prevalence significantly increased with regular blood donation. Female first time and regular blood donors however did not show any significant differences in prevalence of iron deficiency, with both groups exhibiting prevalence rates similar to male regular donors. The association between haemoglobin levels and iron deficiency was poor and the copper sulphate-screening test was found insensitive to anaemia with many donors passing the test and donating blood despite being anaemic. It is concluded that a high prevalence of iron deficiency is present among regular male blood donors and all female donors. Besides, the use of the copper sulphate screening test as a sole criterion for anaemia screening should be reviewed. Ferritin measurements should be included in the routine assessment of blood donors especially among regular blood donors.