[The use of immune checkpoint inhibitors in routine oncology]. / Der Einsatz von Immuncheckpoint-Inhibitoren im onkologischen Alltag.

BACKGROUND: The advent of immune checkpoint inhibitors has dramatically changed the treatment landscape of many different tumor types. In the clinical routine, humanized antibodies against the immune checkpoints cytotoxic T­lymphocyte associated protein 4 (CTLA-4) and programmed cell death 1/programmed cell death ligand 1 (PD1/PD-L1) are generally applied. OBJECTIVE: This article provides an overview of the treatment landscape with immune checkpoint inhibitors, especially for solid tumors in oncology. MATERIAL AND METHODS: Description and discussion of recent trial results as well as current treatment recommendations and treatment approval indications. RESULTS: In the clinical routine seven different immune checkpoint inhibitors are applied in oncology: one anti-CTLA­4 antibody, three anti-PD1 antibodies and three anti-PD-L1 antibodies. On the US market FDA approval for 17 different tumor entities and one agnostic indication (tumors with mismatch repair mechanism deficiency/high microsatellite instability). Long-term remission can be achieved for ca. two thirds of patients with tumor response. CONCLUSION: Clinical benefits for only a part of patients treated with immune checkpoint inhibitors. The understanding of primary and secondary mechanisms of resistance to immune checkpoint inhibitors has just begun to evolve. Combination strategies of immune checkpoint inhibitors with e.g. chemotherapy, new immune checkpoint inhibitors (e.g. anti-LAG3 antibody) or targeted therapies (e.g. CDK4/6, PARP inhibitors) to improve efficacy are under clinical investigation. Reliable and predictive biomarkers are urgently needed.

Forty years of cisplatin-based chemotherapy in muscle-invasive bladder cancer: are we understanding how, who and when?

PURPOSE: For 40 years cisplatin-based chemotherapy has been administered to patients with muscle-invasive bladder cancer (MIBC). The best evidence of its efficacy is found in the context of neoadjuvant chemotherapy (NAC). However, the benefit to the patient is modest, with an improvement in 5-year overall survival of only 5-8%. Approximately 60% of patients still have muscle-invasive disease at cystectomy despite NAC. Selecting patients based on the likelihood of response appears to be a promising strategy to improve on this modest benefit. To realize this promise, researchers are investigating biomarkers for identifying responders and non-responders prior to NAC. METHODS: In this review, we discuss a number of tissue- and liquid-based biomarkers associated with the response to NAC. RESULTS AND CONCLUSIONS: We elaborate biomarkers at the methylation, DNA, RNA and protein levels and give their current status in clinical trials and/or their implementation in daily clinical practice. In particular, detection of alterations in DNA damage repair pathways as well as molecular subtypes seems to be a promising method for identifying responders to NAC. Furthermore, we illustrate liquid-based biomarkers. Circulating tumor DNA (ctDNA) in patient blood and urine appear to offer an elegant way for biological characterization of MIBC. Recent data show that the presence of ctDNA is limited in patients with localized MIBC being considered for NAC. At this disease stage, ctDNA in patient urine may be more promising for the genomic characterization of MIBC. However, ctDNA in blood or urine has not yet been rigorously investigated in this clinical context.

[Immunotherapies - Overview, mode of action and clinical implications]. / Immuntherapie ­ Übersicht, Wirkmechanismen, Anwendung.

Immunotherapies - Overview, mode of action and clinical implications Abstract. The introduction of immunotherapies has led to major advances in the treatment of cancer patients. The mainstays of immunotherapies in clinical routine are immune checkpoint inhibitors. Immune checkpoints like CTLA-4 or the PD-1 / PD-L1 axis are important contributors to the immune homeostasis by preventing overshooting immune responses against pathogens and thus preventing collateral damage to normal tissue, or by preventing autoimmunity. However, immune checkpoints can impede the development of an efficient anti-tumor immune response. Thus, therapeutic monoclonal antibodies against CTLA-4 and PD-1 or PD-L1 displayed remarkable clinical activity such as complete sustained clinical remission even in patients bearing multiple metastases. Malignant melanoma, non-small cell lung cancer or Hodgkin's lymphoma are examples of cancer entities with especially well clinical responses to immune checkpoint inhibitors. This fast-developing field is rapidly expanding the indications for immune checkpoint inhibitors and combinations with other therapeutic strategies like vessel-modulating agents or classical chemotherapy are in preclinical and clinical testing. In this article, the mechanistic principles of immune checkpoint inhibition and their clinical applications are illustrated.

Functional interplay of SP family members and nuclear factor Y is essential for transcriptional activation of the human Calreticulin gene.

Calreticulin (CALR) is a highly conserved, multifunctional protein involved in a variety of cellular processes including the maintenance of intracellular calcium homeostasis, proper protein folding, differentiation and immunogenic cell death. More recently, a crucial role for CALR in the pathogenesis of certain hematologic malignancies was discovered: in clinical subgroups of acute myeloid leukemia, CALR overexpression mediates a block in differentiation, while somatic mutations have been found in the majority of patients with myeloproliferative neoplasms with nonmutated Janus kinase 2 gene (JAK2) or thrombopoietin receptor gene (MPL). However, the mechanisms underlying CALR promoter activation have insufficiently been investigated so far. By dissecting the core promoter region, we could identify a functional TATA-box relevant for transcriptional activation. In addition, we characterized two evolutionary highly conserved cis-regulatory modules (CRMs) within the proximal promoter each composed of one binding site for the transcription factors SP1 and SP3 as well as for the nuclear transcription factor Y (NFY) and we verified binding of these factors to their cognate sites in vitro and in vivo.

Protein disulfide isomerase blocks CEBPA translation and is up-regulated during the unfolded protein response in AML.

Deregulation of the myeloid key transcription factor CEBPA is a common event in acute myeloid leukemia (AML). We previously reported that the chaperone calreticulin is activated in subgroups of AML patients and that calreticulin binds to the stem loop region of the CEBPA mRNA, thereby blocking CEBPA translation. In this study, we screened for additional CEBPA mRNA binding proteins and we identified protein disulfide isomerase (PDI), an endoplasmic reticulum (ER) resident protein, to bind to the CEBPA mRNA stem loop region. We found that forced PDI expression in myeloid leukemic cells in fact blocked CEBPA translation, but not transcription, whereas abolishing PDI function restored CEBPA protein. In addition, PDI protein displayed direct physical interaction with calreticulin. Induction of ER stress in leukemic HL60 and U937 cells activated PDI expression, thereby decreasing CEBPA protein levels. Finally, leukemic cells from 25.4% of all AML patients displayed activation of the unfolded protein response as a marker for ER stress, and these patients also expressed significantly higher PDI levels. Our results indicate a novel role of PDI as a member of the ER stress-associated complex mediating blocked CEBPA translation and thereby suppressing myeloid differentiation in AML patients with activated unfolded protein response (UPR).

Genomic analysis of single cytokeratin-positive cells from bone marrow reveals early mutational events in breast cancer.

Chromosomal instability in human breast cancer is known to take place before mammary neoplasias display morphological signs of invasion. We describe here the unexpected finding of a tumor cell population with normal karyotypes isolated from bone marrow of breast cancer patients. By analyzing the same single cells for chromosomal aberrations, subchromosomal allelic losses, and gene amplifications, we confirmed their malignant origin and delineated the sequence of genomic events during breast cancer progression. On this trajectory of genomic progression, we identified a subpopulation of patients with very early HER2 amplification. Because early changes have the highest probability of being shared by genetically unstable tumor cells, the genetic characterization of disseminated tumor cells provides a novel rationale for selecting patients for targeted therapies.

Adding bendamustine to melphalan before ASCT improves CR rate in myeloma vs. melphalan alone: A randomized phase-2 trial.

Definite cure remains exceptional in myeloma patients even after high-dose chemotherapy (HDCT) with melphalan (Mel) and autologous stem cell transplantation (ASCT). Thus, improving efficacy of HDCT in MM remains an unresolved issue. This randomized phase II trial compared standard 200 mg/m2 Mel HDCT to experimental HDCT with 200 mg/m2 bendamustine, given both at days -4 and -3, combined with 100 mg/m2 melphalan at days -2 and -1 (BenMel) before ASCT as first-line consolidation in myeloma patients. The primary endpoint aimed to identify at least a 15% improvement in the complete remission rate (stringent CR + CR) after HDCT with BenMel compared with Mel alone. A total of 120 MM patients were 1:1 randomized. The rate of sCR/CR after ASCT was higher in BenMel than in Mel treated patients (70.0% vs. 51.7%; p = 0.039). Three patients in the BenMel group (5.0%) had reversible acute renal insufficiency compared with none in Mel patients. Minimal residual disease negativity (<10-5) by flow cytometry was observed in 26 (45.6%) BenMel patients and 22 (37.9%) in the Mel group (p = 0.375). Our data suggest that BenMel HDCT is safe and improves the sCR/CR rate compared with standard Mel alone.

Unfolded protein response suppresses CEBPA by induction of calreticulin in acute myeloid leukaemia.

The unfolded protein response (UPR) is triggered by the accumulation of misfolded proteins within the endoplasmic reticulum (ER). The role of the UPR during leukemogenesis is unknown so far. Here, we studied the induction of mediators of the UPR in leukaemic cells of AML patients. Increased expression of the spliced variant of the X-box binding protein 1 (XBP1s) was detected in 17.4% (16 of 92) of AML patients. Consistent with activated UPR, this group also had increased expression of ER-resident chaperones such as the 78 kD glucose-regulated protein (GRP78) and of calreticulin. Conditional expression of calreticulin in leukaemic U937 cells was found to increase calreticulin binding to the CEBPA mRNA thereby efficiently blocking translation of the myeloid key transcription factor CEBPA and ultimately affecting myeloid differentiation. Consequently, leukaemic cells from AML patients with activated UPR and thus increased calreticulin levels showed in fact suppressed CEBPA protein expression. We identified two functional ER stress response elements (ERSE) in the calreticulin promoter. The presence of NFY and ATF6, as well as an intact binding site for YY1 within these ERSE motifs were essential for mediating sensitivity to ER stress and activation of calreticulin. Thus, we propose a model of the UPR being activated in a considerable subset of AML patients through induction of calreticulin along the ATF6 pathway, thereby ultimately suppressing CEBPA translation and contributing to the block in myeloid differentiation.

Activation of the unfolded protein response is associated with favorable prognosis in acute myeloid leukemia.

PURPOSE: The unfolded protein response is triggered by the accumulation of misfolded proteins within the endoplasmic reticulum. Previous studies suggest that the unfolded protein response is activated in some cancer cell lines and involved in tumor development. The role of the unfolded protein response during leukemogenesis is unknown thus far. EXPERIMENTAL DESIGN: Here, we assessed the induction of key effectors of the unfolded protein response in leukemic cells at diagnosis of 105 acute myeloid leukemia (AML) patients comprising all subtypes. We determined the formation of the spliced variant of the X-box-binding protein 1 (XBP1) mRNA, as well as expression levels of calreticulin, GRP78, and CHOP mRNA. RESULTS: The formation of the spliced variant of XBP1s was detectable in 16.2% (17 of 105) of AML patients. Consistent with activated unfolded protein response, this group also had significantly increased expression of calreticulin, GRP78, and CHOP. AML patients with activated unfolded protein response had lower WBC counts, lactate dehydrogenase levels, and more frequently, secondary AML. The incidence of fms-related tyrosine kinase 3 (FLT3) mutations was significantly lower in patients with activated unfolded protein response. In addition, an association was observed between activated unfolded protein response and deletion of chromosome 7. Finally, the clinical course of AML patients with activated unfolded protein response was more favorable with lower relapse rate (P = 0.0182) and better overall (P = 0.041) and disease-free survival (P = 0.022). CONCLUSIONS: These results suggest that the unfolded protein response is activated in a considerable subset of AML patients. AML patients with activated unfolded protein response present specific clinical characteristics and a more favorable course of the disease.

Swiss experience of atezolizumab for platinum-pretreated urinary tract carcinoma: the SAUL study in real-world practice.

AIMS OF THE STUDY: Atezolizumab is an approved therapy for urothelial carcinoma based on results from the IMvigor 210 and IMvigor211 phase II and III trials. The global SAUL study evaluated atezolizumab in a broader patient population more representative of real-world populations. Among approximately 1000 patients treated in SAUL, 25 were treated in Swiss oncology centres. We evaluated outcomes in these patients to provide a better understanding of atezolizumab treatment for urinary tract carcinoma in Swiss clinical practice. METHODS: Eligible patients had locally advanced or metastatic urothelial or non-urothelial urinary tract carcinoma that had progressed during or after one to three prior therapies for inoperable, locally advanced or metastatic disease. Patient populations typically excluded from clinical trials (e.g., patients with renal impairment, treated central nervous system [CNS] metastases, stable controlled autoimmune disease or Eastern Cooperative Oncology Group performance status 2) were also eligible. All patients received atezolizumab 1200 mg every 3 weeks until loss of clinical benefit or unacceptable toxicity. The primary endpoint was safety. Secondary endpoints included overall survival (OS), overall response rate (ORR) and disease control rate (DCR). RESULTS: All 25 Swiss patients had previously received a gemcitabine/platinum doublet. Disease had progressed within 12 months of platinum-based therapy in all but one patient, and 19 (76%) had received one prior line of therapy for metastatic disease. The median duration of atezolizumab therapy was six cycles (range 1–27) corresponding to 3.6 months. Five patients (20%) had received >20 cycles and four (16%) remained on treatment at the data cut-off. Grade 3 adverse events (AEs) occurred in 13 patients (52%) and were considered to be treatment-related in four patients (16%; liver enzyme increases, musculoskeletal pain, diverticulitis and autoimmune hepatitis). There was one grade 4 AE (hypercalcaemia) and no grade 5 AEs. After median follow-up of 17.3 months, median OS was 7.9 months (95% confidence interval [CI] 5.3–not evaluable), the 1-year OS rate was 47% (95% CI 27–65%), the ORR was 12% (95% CI 3–31%) and the DCR was 40% (95% CI 21–61%). Durable clinical benefit (>1 year on treatment) was observed in seven patients (28%), including one with CNS metastases and one with small-cell carcinoma. CONCLUSIONS: Atezolizumab is an active treatment option for platinum-pretreated urinary tract carcinoma, including patients with conditions that typically exclude them from clinical trials. (Trial registration no.: NCT02928406).

Solid cancer development in solid organ transplant recipients within the Swiss Transplant Cohort Study.

In solid organ transplant recipients (sOTRs), 5 years after transplantation cancer is a relevant cause of death. We aimed to report cancer incidence in the Swiss Transplant Cohort Study (STCS) between 2008 and 2014 and conducted a prospective cohort study of kidney, heart, lung, pancreas and liver transplant recipients enrolled into the STCS by retrospective analysis of collected data. The STCS provided data on 2758 solid organ transplants. In total, 134 cases of cancer were observed (30 liver, 21 prostate, 18 lung, 13 kidney, 52 other cancers). Standardised incidence ratios (SIRs) were highest for liver cancer, kidney cancer, thyroid cancer, gastric cancer, bladder cancer, cancer of the oral cavity and the pharynx and for lung cancer. Cancer occurrence differed according to the transplanted organ. Cancers were mainly diagnosed at World Health Organisation (WHO) stages I and IV. Treatment received was mainly surgery and, in some cases, included also radiation and/or chemotherapy. Bladder, kidney, liver, lung and prostate cancer were detected at a younger age compared with the general population. Cumulative hazards for death were increased for transplant recipients with cancer. Solid organ transplant recipients show an organ specific increase of cancer compared with the general Swiss population. Clinical trial registration number: NCT02333279.

Response to first-line treatment and histology are associated with achieving complete remission after the first salvage high-dose chemotherapy in relapsing germ cell tumor patients.

Sequential high-dose chemotherapy (HDCT) with autologous stem cell transplantation (ASCT) is a curative option in relapsing germ cell tumor (GCT) patients, and complete remission (CR) after the first ASCT (early CR2) is associated with favorable outcome. Prognostic factors predicting early CR2 have not been investigated so far. We analyzed consecutive patients with a first relapse of GCT treated with three sequential cycles of carboplatin/etoposide-based HDCT with ASCT in the two largest academic centers in Switzerland. The cohort comprised 96 relapsing GCT patients, with 19 (19.8%) patients achieving early CR2 after the first HDCT cycle. The median progression-free survival and overall survival were not reached in patients achieving early CR2, whereas they were 9.6 months (P = 0.0301) and 34.8 months (P = 0.0684) for patients missing early CR2. Patients with early CR2 more often had CR1 after first-line bleomycin, etoposide, and cisplatin chemotherapy (68.4 vs. 31.6%; P = 0.0037) and an interval longer than 2 years between initial diagnosis and first HDCT (36.8 vs. 15.6%; P = 0.0373), but less often a histology of mixed nonseminomatous tumor (46.8 vs. 21.1%; P = 0.0418). These data suggest that response to first-line chemotherapy, late relapse, and histology are associated with achieving early CR2 after a first HDCT with ASCT in relapsing GCT patients.

Pattern of Care Study in Metastatic Renal-Cell Carcinoma in the Preimmunotherapy Era in Switzerland.

INTRODUCTION: In metastatic renal-cell carcinoma (mRCC), physicians have a plethora of therapeutic choices, with the latest addition of checkpoint inhibitors. However, many questions regarding the best use of the respective drugs remain unanswered. Therefore, it is important to examine and summarize the outcome of real-world experiences to understand the practical value of the various drugs in daily use and foster optimal treatment algorithms for patients with renal-cell carcinoma. We sought to describe the pattern of care in mRCC under circumstances with access to all therapeutic options for patients. PATIENTS AND METHODS: We examined the outcome of patients with mRCC who were treated at 8 major centers in Switzerland, mainly with vascular endothelial growth factor-targeted therapy and mammalian target of rapamycin inhibitors. Data from 110 patients with mRCC who had undergone more than one systemic therapy were collected and analyzed. We assessed the pattern of care for patients with mRCC in an unrestricted health care system and outcomes with regard to the respective treatment sequences. We also studied the compliance of individual therapies with published guidelines and correlated the adherence to outcome. Finally, immediate versus deferred treatment and the number of received therapeutic drug lines were analyzed. RESULTS: Median survival of patients treated with targeted agents for mRCC was 2.0 years. CONCLUSION: Exposure to more than 2 lines of systemic drugs did not improve outcome of patients with mRCC.

Activation of the unfolded protein response in human acute myeloid leukemia.

There is accumulating evidence for the involvement of the unfolded protein response (UPR) in the pathogenesis of many tumor types in humans. This is particularly the case in rapidly growing solid tumors in which the demand for oxygen and nutrients can exceed the supply until new tumor-initiated blood vessels are formed. In contrast, the role of the UPR during leukemogenesis remains largely unknown. Acute myeloid leukemia (AML) is a genetically heterogeneous clonal disorder characterized by the accumulation of somatic mutations in hematopoietic progenitor cells that alter the physiological regulation of self-renewal, survival, proliferation, or differentiation. The CCAAT/enhancer-binding protein alpha (CEBPA) gene is a key myeloid transcription factor and a frequent target for disruption in AML. In particular, translation of CEBPA mRNA can be specifically blocked by binding of the chaperone calreticulin (CALR), a well-established effector of the UPR, to a stem loop structure within the 5' region of the CEBPA mRNA. The relevance of this mechanism was first elucidated in certain AML subtypes carrying the gene rearrangements t(3;21) or inv(16). In our recent work, we could demonstrate the induction of key effectors of the UPR in leukemic cells of AML patients comprising all subtypes (according to the French-American-British (FAB) classification for human AML). The formation of the spliced variant of the X-box binding protein (XBP1s) was detectable in 17.4% (17 of 105) of AML patients. Consistent with an activated UPR, this group had significantly increased expression of the UPR target genes CALR, the 78 kDa glucose-regulated protein (GRP78), and the CCAAT/enhancer-binding protein homologous protein (CHOP). Consistently, in vitro studies confirmed that calreticulin expression was upregulated via activation of the ATF6 pathway in myeloid leukemic cells. As a consequence, CEBPA protein expression was inhibited in vitro as well as in leukemic cells from patients with activated UPR. We therefore propose a model of the UPR being involved in leukemogenesis through induction of calreticulin along the ATF6 pathway, thereby ultimately suppressing CEBPA translation and contributing to the block in myeloid differentiation and cell-cycle deregulation which represent key features of the leukemic phenotype. From a more clinical point of view, the presence of activated UPR in AML patient samples was found to be associated with a favorable disease course.

Inhibition of tissue transglutaminase sensitizes TRAIL-resistant lung cancer cells through upregulation of death receptor 5.

Tissue transglutaminase (TG2) is implicated in cellular processes such as apoptosis and cell migration. Its acyl transferase activity cross-links certain proteins, among them transcription factors were described. We show here that the TG2 inhibitor KCC009 reversed resistance to tumor necrosis factor-related apoptosis-inducing factor (TRAIL) in lung cancer cells. Sensitization required upregulation of death receptor 5 (DR5) but not of death receptor 4. Upregulation of DR5 involved the first intron of the DR5 gene albeit it was independent from p53 and nuclear factor kappa B. In conclusion, inhibition of tissue transglutaminase provides an interesting strategy for sensitization to TRAIL-induced apoptosis in p53-deficient lung cancer cells.

Complexity of miR-223 regulation by CEBPA in human AML.

microRNA-223 (miR-223) can trigger normal granulopoiesis. miR-223 expression is regulated by two distinct CEBPA (CCAAT/enhancer binding protein-alpha) sites. Here, we report that miR-223 is largely suppressed in cells from acute myeloid leukemia (AML) patients. By sequencing, we found that miR-223 suppression in AML is not caused by DNA sequence alterations, nor is it mediated by promoter hypermethylation. The analysis of the individual contribution of both CEBPA sites to miR-223 regulation identified the site upstream of the miR-223 primary transcript as the predominant regulatory element. Our results suggest that miR-223 suppression in AML is caused by impaired miR-223 upstream factors.

Somatic CEBPA mutations are a frequent second event in families with germline CEBPA mutations and familial acute myeloid leukemia.

PURPOSE: The transcription factor CCAAT/enhancer binding protein-alpha (CEBPA) is crucial for normal myeloid differentiation. Mutations in the CEBPA gene are found in subsets of patients with acute myeloid leukemia (AML). Recently, three families were reported in whom several family members had germline CEBPA mutations and subsequently developed AML. Whereas familial AML is considered a rare event, the frequency of CEBPA germline mutations in AML is not known. PATIENTS AND METHODS: In this study, we screened 187 consecutive AML patients for CEBPA mutations at diagnosis. We detected 18 patients (9.6%) with CEBPA mutations. We then analyzed remission samples and constitutive DNA from these patients. RESULTS: We found that two (11.1%) of 18 AML patients with CEBPA mutations carried a germline N-terminal frameshift CEBPA mutation. Interestingly, additional members in the families of both of these patients have been affected by AML, and the germline CEBPA mutations were also observed in these patients. Additional somatic mutations in AML patients with germline CEBPA mutations in the two families comprised in-frame C-terminal CEBPA mutations in two patients, two nonsilent CEBPA point mutations in one patient, and monosomy 7 in one patient. CONCLUSION: This study shows, for the first time to our knowledge, that germline CEBPA mutations are frequently observed among AML patients with CEBPA mutations. Including the families with germline CEBPA mutations reported previously, additional somatic CEBPA mutations represent a frequent second event in AML with germline CEBPA mutations. Our data strongly indicate that germline CEBPA mutations predispose to AML and that additional somatic CEBPA mutations contribute to the development of the disease.

CBFB-SMMHC is correlated with increased calreticulin expression and suppresses the granulocytic differentiation factor CEBPA in AML with inv(16).

The pericentric inversion of chromosome 16, inv(16)(p13q22), is associated with acute myeloid leukemia (AML) subtype M4Eo that is characterized by the presence of myelomonocytic blasts and atypical eosinophils. This rearrangement fuses the CBFB and MYH11 genes, with the latter encoding the smooth muscle myosin heavy chain (SMMHC). The myeloid transcription factor CCAAT/enhancer-binding protein alpha (CEBPA) is crucial for normal granulopoiesis. Alterations of structure and expression of CEBPA have been implicated in particular subtypes of AML. Here, we found that conditional expression of core-binding factor beta (CBFB)-SMMHC in U937 cells suppresses CEBPA protein expression and binding activity. However, CEBPA mRNA levels remained unchanged. No differences were detected in CEBPA mRNA levels in patients with inv(16) AML-M4Eo (n = 12) compared to patients with AML with a normal karyotype and M4 subtype (n = 6), whereas CEBPA protein and binding activity were significantly reduced in patients with CBFB-SMMHC. Furthermore, calreticulin, an inhibitor of CEBPA translation, was induced on mRNA and protein level in CBFB-SMMHC patients with AML and after expression of CBFB-SMMHC in the U937-cell system. Inhibition of calreticulin by siRNA restored CEBPA levels. Our results suggest that modulation of CEBPA by calreticulin represents a novel mechanism involved in the differentiation block in CBFB-SMMHC AML.

SCOMP is superior to degenerated oligonucleotide primed-polymerase chain reaction for global amplification of minute amounts of DNA from microdissected archival tissue samples.

Global genome amplification from formalin-fixed tissues is still problematic when performed with low cell numbers. Here, we tested a recently developed method for whole genome amplification termed "SCOMP" (single cell comparative genomic hybridization) on archival tissues of different ages. We show that the method is very well suited for formalin-fixed paraffin-embedded samples obtained by nuclei extraction or laser microdissection. The polymerase chain reaction (PCR) products can be used for subsequent comparative genomic hybridization, loss of heterozygosity studies, and DNA sequencing. To control for PCR-induced artifacts we amplified genomic DNA isolated from 20 nuclei of archival formalin-fixed, paraffin-embedded nonpathological lymph nodes. Subsequent comparative genomic hybridization revealed the expected balanced profiles. For loss of heterozygosity analysis by microsatellite PCR 60 to 160 cells were sufficient. In comparative experiments the approach turned out to be superior to published degenerated oligonucleotide-primed-PCR protocols. The method provides a robust and valuable tool to study very small cell samples, such as the genomes of dysplastic cells or the clonal evolution within heterogeneous tumors.