Chemotherapeutic alteration of VEGF-/PDGF- and PDGF-Rα/β expression by imatinib in HPV-transformed squamous cell carcinoma compared to HPV-negative HNSCC in vitro

Head and neck squamous cell carcinoma (HNSCC) is an aggressive epithelial malignancy known to be the most common neoplasm appearing in the upper aerodigestive tract. The poor five-year survival rate has remained unchanged in the last decades despite the emergence of improved techniques in surgery, radiation and chemotherapy. In the last 20 years awareness of a subset of squamous cell carcinomas induced by oncogenic forms of the human papilloma virus (HPV) (high-risk types 16 and 18) has increased. The incidence of HPV-associated oropharyngeal cancer is rising, indicating the increased importance of the viral etiology. Cell proliferation, migration, induction of tumor vascularization and carcinogenesis, as well as invasion facilitation is regulated by a variety of angiogenic peptides like PDGF, PDGF-R and VEGF. They might be an encouraging target for biological anticancer therapy by inhibiting disrupted cellular signaling pathways. Imatinib has been shown to target specific tyrosine kinases, inhibiting proliferation in various cancer entities. The purpose of this study was to evaluate the expression pattern of angiogenic factors (VEGF, PDGF and PDGF-R) in HPV-positive (p16-CERV196 SCC) and (-negative squamous cell carcinoma (HNSCC). The study also evaluated the vulnerability of anti-angiogenesis therapy depending on the HPV status as potential treatment modality compared to established platinum-based chemotherapeutic drugs. The different squamous tumor cell lines were incubated with increasing concentrations of carboplatin (3 and 7.5 µmol) and imatinib (18 and 30 µmol). ELISA immunohistochemical methods were carried out after 48, 72, 120, 192 and 240 h. We demonstrated a significant reduction of VEGF and PDGF-Rα/β expression patterns after incubation of imatinib in ELISA and immunohistochemical methods, irrespective of the HPV status of the tumor cells, whereas the application of carboplatin had no impact on the expression of angiogenic peptides. Viral oncogen-transformed squamous cell carcinoma (CERV196) cells were characterized by a reduced susceptibility for an imatinib-altered VEGF expression. Further studies are planned to investigate this observance in HPV-positive HNSCC in vitro. The implementation of a selective molecular anti-angiogenic therapy in established chemotherapeutic regimens may enhance the efficacy of platinum-based chemotherapy without an increased toxicity profile and could thus improve the clinical outcome in HNSCC, irrespective of the HPV status.

Down-regulation of MMP-2 expression due to inhibition of receptor tyrosine kinases by imatinib and carboplatin in HNSCC

Squamous cell carcinoma of the head and neck (HNSCC) is the most common neoplasm arising in the upper aerodigestive tract. Unfortunately, the survival for this type of cancer has not improved significantly in the past 25 years. To enhance the survival rate multimodal therapy regimens have been set up. In these regimens chemotherapy plays a pivotal role in the majority of advanced cases. Transmembrane protein- tyrosine kinases (PTK) are fundamental elements of the signal transduction. In consequence, they might be promising targets for cancer therapy. Imatinib (STI 571) was originally designed to inhibit the BCR-ABL tyrosine kinase in chronic myeloid leukemia. But imatinib also has an inhibitory impact on the PTK receptor c-kit and on its PTK activity. Furthermore, growth and invasion of HNSCC are strongly influenced by the extracellular matrix (ECM). The ECM is altered by matrix metalloproteinases (MMP). In this study, we incubated different HNSCC cell lines with rising concentrations of imatinib and/or carboplatin. After an incubation time of up to 10 days, we evaluated c-kit, MMP-2 and MMP-14 by ELISA techniques and immunohistochemical methods. Especially the combination of 7.5 μmol carboplatin with 30 μmol imatinib resulted in a significant decrease in MMP-2 expression in all observed cell lines (p<0.05). We did not demonstrate a significant alteration in c-kit expression by imatinib and carboplatin. We observed an increase in apoptosis in HNSCC cells by the combination of the two observed chemotherapeutic drugs. In all cell lines tested, expression of c-kit and MMP could be demonstrated. Our results indicate that MMP-2 expression was suppressed in the presence of imatinib. Thus, imatinib may exert in part its inhibitory effect on malignant cell growth via the blockage of the signal transduction of PTK receptors. Further studies are warranted, especially one keeping in mind the moderate toxicity of imatinib.

Synergistic effects of imatinib and carboplatin on VEGF, PDGF and PDGF-Rα/ß expression in squamous cell carcinoma of the head and neck in vitro

Head and neck squamous cell carcinoma (HNSCC) is an aggressive epithelial malignancy. The development of new treatment modalities in order to improve long-term survival of patients with HNSCC is imperative. Numerous studies have demonstrated that carcinogenesis and tumor cell dissemination is influenced by the tumor microenvironment. The protein-kinase-receptors (PTKs) are essential elements of the intracellular signal transduction pathway and regulate cell growth, development and apoptosis. Cell proliferation, migration, induction of tumor vascularization and carcinogenesis, invasion is regulated by a variety of angiogenic factors, such as PDGF (platelet-derived growth factor), VEGF (vascular endothelial growth factor) and their respective tyrosine kinase receptors (PDGF-R and VEGF-R). They present promising targets for anti-cancer therapy through abrogation of impaired signaling pathways. Indeed, imatinib, a small molecule drug targeting these protein kinases, has antiproliferative effects in several cancer types. The purpose of this study was to investigate the potential synergism of imatinib and carboplatin on the expression of PDGF, PDGF-R α/ß and VEGF in different HNSCC cell lines. Several tumor cell lines were subjected to increasing concentrations of carboplatin (3 and 7.5 µmol/l) and imatinib (18 and 30 µmol/l) and ELISA, immunohistochemical methods and RQ-PRC after 48, 72, 120 and 240 h were used to assess their expression levels. While PDGF-Rα/ß expression was unimpaired at lower imatinib concentrations (18 µmol/l), PDGF-Rα/ß expression was suppressed at 30 µmol/l, and suppression was enhanced by the presence of carboplatin. By RQ-PCR, a significant reduction of PDGF-Rα/ß expression was detected (p<0.5). We observed explicit significant reduction in VEGF levels with increasing concentrations of imatinib and with the combination of the two chemotherapeutic drugs (p<0.5). We report for the first time evidence of synergism of imatinib and carboplatin in suppressing VEGF, PDGF and PDGF-Rα/ß expression in HNSCC.

Dasatinib in imatinib-resistant or imatinib-intolerant chronic myeloid leukemia in blast phase after 2 years of follow-up in a phase 3 study: efficacy and tolerability of 140 milligrams once daily and 70 milligrams twice daily

BACKGROUND

In a phase 3 study, the authors assessed the effects of dasatinib at doses of 140 mg once daily and 70 mg twice daily in patients who had either chronic myeloid leukemia (CML) in advanced phases or Philadelphia chromosome-positive acute lymphoblastic leukemia and were resistant or intolerant to imatinib. In the current report, the results for patients with CML in blast phase after 2 years of follow-up are reported.

METHODS

Patients were stratified according to whether they had CML in myeloid blast phase (MBP-CML) or in lymphoid blast phase (LBP-CML) and were randomized (1:1) within each stratum to receive either oral dasatinib 140 mg once daily or 70 mg twice daily.

RESULTS

In patients with MBP-CML, the major hematologic response rate was 28% for both regimens; and, in patients with LBP-CML, the major hematologic response rate was 42% for once-daily dasatinib and 32% for twice-daily dasatinib. The major cytogenetic response rates were 25% for once-daily dasatinib and 28% for twice-daily dasatinib in patients with MBP-CML, and the respective rates in patients with LBP-CML were 50% and 40%. The overall survival rate at 24 months was 24% for once-daily dasatinib and 28% for twice-daily dasatinib in patients with MBP-CML, and the respective values in patients with LBP-CML were 21% and 16%. Adverse events indicated a trend toward improved tolerability for the once-daily regimen.

CONCLUSIONS

The current results suggested that dasatinib 140 mg once daily had similar efficacy and improved tolerability relative to the 70-mg twice-daily regimen in patients with imatinib-resistant, blast phase CML.

KRAS and BRAF mutations and PTEN expression do not predict efficacy of cetuximab-based chemoradiotherapy in locally advanced rectal cancer

PURPOSE

Mutations in KRAS and BRAF genes as well as the loss of expression of phosphatase and tensin homolog (PTEN) (deleted on chromosome 10) are associated with impaired activity of antibodies directed against epidermal growth factor receptor in patients with metastatic colorectal cancer. The predictive and prognostic value of the KRAS and BRAF point mutations as well as PTEN expression in patients with locally advanced rectal cancer (LARC) treated with cetuximab-based neoadjuvant chemoradiotherapy is unknown.

METHODS AND MATERIALS

We have conducted phase I and II trials of the combination of weekly administration of cetuximab and irinotecan and daily doses of capecitabine in conjunction with radiotherapy (45 Gy plus 5.4 Gy) in patients with LARC (stage uT3/4 or uN+). The status of KRAS and BRAF mutations was determined with direct sequencing, and PTEN expression status was determined with immunohistochemistry testing of diagnostic tumor biopsies. Tumor regression was evaluated by using standardized regression grading, and disease-free survival (DFS) was calculated according to the Kaplan-Meier method.

RESULTS

A total of 57 patients were available for analyses. A total of 31.6% of patients carried mutations in the KRAS genes. No BRAF mutations were found, while the loss of PTEN expression was observed in 9.6% of patients. Six patients achieved complete remission, and the 3-year DFS rate was 73%. No correlation was seen between tumor regression or DFS rate and a single marker or a combination of all markers.

CONCLUSIONS

In the present series, no BRAF mutation was detected. The presence of KRAS mutations and loss of PTEN expression were not associated with impaired response to cetuximab-based chemoradiotherapy and 3-year DFS.

Cause and management of therapy resistance

A minority of patients treated with imatinib are either refractory to imatinib or eventually relapse. Relapse frequently depends on re-emergence of BCR-ABL kinase activity but may also indicate BCR-ABL-independent disease progression. Over 90 point mutations coding for single amino acid substitutions in the BCR-ABL kinase domain have been isolated from CML patients resistant to imatinib treatment. These mutations affect amino acids involved in imatinib binding or in regulatory regions of the BCR-ABL kinase domain, resulting in decreased sensitivity to imatinib while retaining aberrant kinase activity. The early detection of BCR-ABL mutants during therapy may aid in risk stratification as well as molecular-based treatment decisions. Therapeutic strategies of imatinib resistant disease include novel tyrosine kinase inhibitors with activity against imatinib-resistant mutations and/or with inhibition of alternative pathways, dose escalation to optimise imatinib levels, treatment interruption to stop selection of resistant cells and allogeneic stem cell transplantation in eligible patients.

Sustained molecular response with interferon alfa maintenance after induction therapy with imatinib plus interferon alfa in patients with chronic myeloid leukemia

PURPOSE

Imatinib induces sustained remissions in patients with chronic myelogenous leukemia (CML), but fails to eradicate CML stem cells. This is of major concern regarding the issues of cure, long-term imatinib tolerability, and imatinib resistance. We therefore asked whether interferon alfa-2a (IFN) alone could maintain molecular remissions achieved by a prior combination therapy with imatinib and IFN.

PATIENTS AND METHODS

Imatinib therapy was stopped in 20 patients who had concomitantly been pretreated with imatinib and IFN for a median of 2.4 years (range, 0.2 to 4.8 years) and 2.5 years (range, 0.2 to 4.9 years), respectively. After imatinib discontinuation, remission status was monitored monthly by quantitative analysis of the peripheral-blood BCR-ABL mRNA levels using real-time polymerase chain reaction. Proteinase-3 expression and proteinase-3-specific cytotoxic T cells (CTLs) were longitudinally measured to assess putative markers of IFN response.

RESULTS

With a median time of 2.4 years after imatinib withdrawal (range, 0.5 to 4.0 years), 15 (75%) of 20 patients remained in remission. The number of patients in complete molecular remission increased under IFN from two patients at baseline to five patients after 2 years. Relapses occurred in five patients within 0.4 years (range, 0.2 to 0.8 years), but patients underwent rescue treatment with imatinib, re-establishing molecular remission. IFN therapy was associated with an increase in the expression of leukemia-associated antigen proteinase 3 and induction of proteinase-3-specific CTLs.

CONCLUSION

Treatment with IFN enables discontinuation of imatinib in most patients after prior imatinib/IFN combination therapy and may result in improved molecular response. Induction of a proteinase-3-specific CTL response by IFN may contribute to this effect.

Screening for diverse PDGFRA or PDGFRB fusion genes is facilitated by generic quantitative reverse transcriptase polymerase chain reaction analysis

BACKGROUND

Rapid identification of diverse fusion genes with involvement of PDGFRA or PDGFRB in eosinophilia-associated myeloproliferative neoplasms is essential for adequate clinical management but is complicated by the multitude and heterogeneity of partner genes and breakpoints.

DESIGN AND METHODS

We established a generic quantitative reverse transcriptase polymerase chain reaction to detect overexpression of the 3'-regions of PDGFRA or PDGFRB as a possible indicator of an underlying fusion.

RESULTS

At diagnosis, all patients with known fusion genes involving PDGFRA (n=5; 51 patients) or PDGFRB (n=5; 7 patients) showed significantly increased normalized expression levels compared to 191 patients with fusion gene-negative eosinophilia or healthy individuals (PDGFRA/ABL: 0.73 versus 0.0066 versus 0.0064, P<0.0001; PDGFRB/ABL: 196 versus 3.8 versus 5.85, P<0.0001). The sensitivity and specificity of the activation screening test were, respectively, 100% and 88.4% for PDGFRA and 100% and 94% for PDGFRB. Furthermore, significant overexpression of PDGFRB was found in a patient with an eosinophilia-associated myeloproliferative neoplasm with uninformative cytogenetics and an excellent response to imatinib. Subsequently, a new SART3-PDGFRB fusion gene was identified by 5'-rapid amplification of cDNA ends polymerase chain reaction (5'-RACE-PCR).

CONCLUSIONS

Quantitative reverse transcriptase polymerase chain reaction analysis is a simple and useful adjunct to standard diagnostic assays to detect clinically significant overexpression of PDGFRA and PDGFRB in eosinophilia-associated myeloproliferative neoplasms or related disorders.

TFG, a target of chromosome translocations in lymphoma and soft tissue tumors, fuses to GPR128 in healthy individuals

BACKGROUND

The formation of fusion genes plays roles in both oncogenesis and evolution by facilitating the acquisition of novel functions. Here we describe the first example of a human polymorphic in-frame fusion of two unrelated genes associated with a copy number variant.

DESIGN AND METHODS

Array comparative genomic hybridization was used to identify cryptic oncogenic fusion genes. Fusion gene structure and origin was examined using molecular biological and computational methods. Phenotype associations were examined using PopGen cohorts.

RESULTS

Targeted array comparative genomic hybridization to identify cryptic oncogenic fusion genes in patients with atypical myeloproliferative neoplasms identified a 111 kb amplification with breakpoints within the TRK-fused gene (TFG, a target of translocations in lymphoma and thyroid tumors) and G-protein-coupled receptor 128 (GPR128) resulting in an expressed in-frame TFG-GPR128 fusion transcript. The fusion gene was also identified in healthy individuals at a frequency of 0.02 (3/120). Normally both genes are in identical orientations with TFG immediately downstream of GPR128. In individuals with a copy number variant amplification, one or two copies of the TFG-GPR128 fusion are found between the two parental genes. The breakpoints share a region of microhomology, and haplotype and microsatellite analysis indicate a single ancestral origin. Analysis of PopGen cohorts showed no obvious phenotype association. An in silico search of EST databases found no other copy number variant amplification-associated fusion transcripts, suggesting that this is an uncommon event. Conclusions The finding of a polymorphic gene fusion in healthy individuals adds another layer to the complexity of human genome variation and emphasizes the importance of careful discrimination of oncogenic changes found in tumor samples from non-pathogenic normal variation.

Impact of baseline BCR-ABL mutations on response to nilotinib in patients with chronic myeloid leukemia in chronic phase

PURPOSE

Nilotinib is a second-generation tyrosine kinase inhibitor indicated for the treatment of patients with chronic myeloid leukemia (CML) in chronic phase (CP; CML-CP) and accelerated phase (AP; CML-AP) who are resistant to or intolerant of prior imatinib therapy. In this subanalysis of a phase II study of nilotinib in patients with imatinib-resistant or imatinib-intolerant CML-CP, the occurrence and impact of baseline and newly detectable BCR-ABL mutations were assessed.

PATIENTS AND METHODS

Baseline mutation data were assessed in 281 (88%) of 321 patients with CML-CP in the phase II nilotinib registration trial.

RESULTS

Among imatinib-resistant patients, the frequency of mutations at baseline was 55%. After 12 months of therapy, major cytogenetic response (MCyR) was achieved in 60%, complete cytogenetic response (CCyR) in 40%, and major molecular response (MMR) in 29% of patients without baseline mutations versus 49% (P = .145), 32% (P = .285), and 22% (P = .366), respectively, of patients with mutations. Responses in patients who harbored mutations with high in vitro sensitivity to nilotinib (50% inhibitory concentration [IC(50)] <or= 150 nM) or mutations with unknown nilotinib sensitivity were equivalent to those responses for patients without mutations (not significant). Patients with mutations that were less sensitive to nilotinib in vitro (IC(50) > 150 nM; Y253H, E255V/K, F359V/C) had less favorable responses, as 13%, 43%, and 9% of patients with each of these mutations, respectively, achieved MCyR; none achieved CCyR.

CONCLUSION

For most patients with imatinib resistance and with mutations, nilotinib offers a substantial probability of response. However, mutational status at baseline may influence response. Less sensitive mutations that occurred at three residues defined in this study, as well as the T315I mutation, may be associated with less favorable responses to nilotinib.

Dasatinib in the treatment of chronic myeloid leukemia in accelerated phase after imatinib failure: the START a trial

PURPOSE Patients with chronic myelogenous leukemia in accelerated phase (CML-AP) that is resistant or intolerant to imatinib have limited therapeutic options. Dasatinib, a potent inhibitor of BCR-ABL and SRC-family kinases, has efficacy in patients with CML-AP who have experienced treatment failure with imatinib. We now report follow-up data from the full patient cohort of 174 patients enrolled onto a phase II trial to provide a more complete assessment of the efficacy and safety of dasatinib in this population. PATIENTS AND METHODS Patients with imatinib-resistant (n = 161) or -intolerant (n = 13) CML-AP received dasatinib 70 mg orally twice daily. Results At a median follow-up of 14.1 months (treatment duration, 0.1 to 21.7 months), major and complete hematologic responses were attained by 64% and 45% of patients, respectively, and major and complete cytogenetic responses were achieved in 39% and 32% of patients, respectively. Responses were achieved irrespective of imatinib status (resistant or intolerant), prior stem-cell transplantation, or the presence of prior BCR-ABL mutation. The 12-month progression-free survival and overall survival rates were 66% and 82%, respectively. Dasatinib was generally well tolerated; the most frequent nonhematologic severe treatment-related adverse event was diarrhea (52%; grade 3 to 4, 8%). Cytopenias were common, including grade 3 to 4 neutropenia (76%) and thrombocytopenia (82%). Pleural effusion occurred in 27% of patients (grade 3 to 4, 5%). CONCLUSION Dasatinib is effective in patients with CML-AP after imatinib treatment failure.

mRNA expression of platelet-derived growth factor receptor-beta and C-KIT: correlation with pathologic response to cetuximab-based chemoradiotherapy in patients with rectal cancer

PURPOSE

Deviant expression of platelet-derived growth factor receptor-beta (PDGFRbeta) and c-kit was shown in patients with colorectal cancer. In the present study, mRNA expression of PDGFRbeta and c-kit in 33 patients with locally advanced rectal cancer undergoing preoperative chemoradiotherapy with cetuximab/capecitabine/irinotecan in correlation with the tumor regression rate was investigated.

METHODS AND MATERIALS

Pretherapeutic biopsy cores and tumor material from the resected specimens were collected in parallel with normal rectal mucosa. The expression levels of PDGFRbeta and c-kit were measured by quantitative polymerase chain reaction. Tumors were classified as good responders (tumor regression grade [TRG], 2-3) or poor responders (TRG, 0-1).

RESULTS

The TRG evaluation of the resected specimen was TRG 0-1 in 11 and TRG 2-3 in 22. The median normalized ratios in the pretreatment mucosa vs. tumor biopsy cores was as follows: PDGFRbeta ratio of 15.2 vs. 49.5 (p <0.0001) and c-kit ratio of 0.94 vs. 0.67 (p = 0.014). The same tendency was observed for the median PDGFRbeta ratios after chemoradiotherapy completion: 34.2 vs. 170.0 (p <0.0001). The PDGFRbeta and c-kit mRNA expression values in the pretreatment tumor biopsy cores were lower than the values in the resected specimens: PDGFRbeta ratio 49.5 vs. 170.0 (p = 0.0002) and c-kit ratio 0.67 vs. 1.1 (p = 0.0003). Nevertheless, no correlation was seen between the pretherapeutic PDGFRbeta and c-kit mRNA expression and the pathologic regression rate.

CONCLUSION

Cetuximab-based chemoradiotherapy increased PDGFRbeta levels even further compared with the pretreatment samples and deserves further investigation.

ABL single nucleotide polymorphisms may masquerade as BCR-ABL mutations associated with resistance to tyrosine kinase inhibitors in patients with chronic myeloid leukemia

The BCR-ABL K247R change is based on a rare single nucleotide polymorphism occurring likewise in healthy controls and non-hematologic cell types. Despite its juxtaposition to the P-loop, functional analysis showed no alteration compared to non-mutated BCR-ABL. We sought to investigate if other changes in the BCR-ABL kinase domain should be considered as single nucleotide polymorphisms rather than acquired mutations. A total of 911 chronic myeloid leukemia patients after failure or suboptimal response to imatinib were screened for BCR-ABL kinase domain mutations. Single nucleotide polymorphism analysis was based on the search for nucleotide changes in corresponding normal, non-translocated ABL alleles by ABL allele-specific PCR following mutation analysis. In addition to the K247R polymorphism we uncovered five new single nucleotide polymorphisms within the BCR-ABL kinase domain; two of them led to amino acid changes. Single nucleotide polymorphisms could theoretically contribute to primary but not to secondary resistance to tyrosine kinase inhibitors and must therefore be distinguished from acquired mutations. Novel point mutations should be confirmed by analyzing the normal ABL alleles to exclude polymorphisms.

Suitability of the PAXgene system to stabilize bone marrow RNA in imatinib-resistant patients with chronic myeloid leukemia

BACKGROUND

Optimum sample quality is a crucial requirement for molecular monitoring of patients with chronic myeloid leukemia (CML) on therapy. Bedside RNA stabilization systems (e.g., PAXgene) have been developed to inhibit RNA degradation during shipment of samples from the clinical site to the specialized laboratory. In CML, blood but not bone marrow samples have been examined using RNA stabilization in previous studies. Therefore, we sought to investigate the applicability of the PAXgene system for bone marrow samples in CML.

METHODS

Simultaneously stabilized blood and bone marrow samples were obtained from 55 imatinib-resistant CML patients to compare RNA yield and purity, expression of two housekeeping genes (total ABL and beta-glucuronidase; GUS) by quantitative reverse-transcriptase polymerase chain reaction, BCR-ABL expression (ratios BCR-ABL/ABL and BCR-ABL/GUS), and BCR-ABL kinase domain mutations analyzed by denaturing high-performance liquid chromatography and direct sequencing.

RESULTS

RNA extraction revealed high-quality RNA derived from both stabilized blood and bone marrow samples. RNA yield was significantly higher in bone marrow (median 9.9 microg RNA/mL bone marrow) than in blood (median 4.3 microg RNA/mL blood) (p=0.0005). The number of housekeeping gene transcripts was comparable in blood and bone marrow (median ABL copies/2 microL cDNA 13,260 vs. 25,590; median GUS copies/2 microL cDNA 35,490 vs. 60,200; n.s.). Further, ratios BCR-ABL/ABL (blood vs. bone marrow, median 47% vs. 57%) and ratios BCR-ABL/GUS (blood vs. bone marrow, median 26% vs. 21%) were not significantly different. Results of mutation analysis corresponded in 51 out of 55 patients (93%), whereas moderate differences were observed in four patients.

CONCLUSIONS

We conclude that bone marrow can be effectively stabilized using the PAXgene system and shows concordance with blood in terms of BCR-ABL mRNA quantification and mutation analysis in imatinib-resistant CML patients.

Phospho-CRKL monitoring for the assessment of BCR-ABL activity in imatinib-resistant chronic myeloid leukemia or Ph+ acute lymphoblastic leukemia patients treated with nilotinib

Actual BCR-ABL kinase inhibition in vivo as determined by phospho-CRKL (pCRKL) monitoring has been recognized as a prognostic parameter in patients with chronic myelogenous leukemia treated with imatinib. We report a biomarker sub-study of the international phase I clinical trial of nilotinib (AMN107) using the established pCRKL assay in imatinib-resistant chronic myeloid leukemia or Ph+ acute lymphoblastic leukemia. A minimum dose (200 mg) required for effective BCR-ABL inhibition in imatinib resistant/intolerant leukemia was determined. The pre-clinical activity profile of nilotinib against mutant BCR-ABL was largely confirmed. Substantial differences between peripheral blood baseline pCRKL/CRKL ratios were observed when comparing chronic myeloid leukemia with Ph+ acute lymphoblastic leukemia. Finally, rapid BCR-ABL-reactivation shortly after starting nilotinib treatment was seen in acute lymphoblastic leukemia patients with progressive disease carrying the P-loop mutations Y253H, E255K, or mutation T315I. Monitoring the actual BCR-ABL inhibition in nilotinib treated patients using pCRKL as a surrogate is a means to establish effective dosing and to characterize resistance mechanisms against nilotinib.

Dynamics of BCR-ABL mutated clones prior to hematologic or cytogenetic resistance to imatinib

background: Mutations of the BCR-ABL tyrosine kinase domain constitute a major cause of resistance to tyrosine kinase inhibitors in patients with chronic myeloid leukemia. We sought to improve the diagnostic armamentarium by screening and to analyze the dynamics of mutated clones in chronic myeloid leukemia patients who experienced hematologic or cytogenetic relapse.

DESIGN AND METHODS

Ninety-five patients who relapsed during imatinib therapy were screened for BCR-ABL kinase domain mutations using sensitive denaturing high-performance liquid chromatography (D-HPLC) and direct sequencing. To investigate the dynamics of mutated clones D-HPLC was applied to 453 cDNA samples tracking back from relapse towards the start of imatinib therapy.

RESULTS

Twenty-two different point mutations affecting 18 amino acids were detectable in 46/79 (58%) and in 7/16 patients (44%) with hematologic or cytogenetic relapse, respectively. A deletion of 81 nucleotides (del248-274) of ABL exon 4 was observed in two patients. Three patients had exclusively single nucleotide polymorphisms (K247R, T315T, E499E, n=1 each) within the BCR-ABL kinase domain. In patients harboring mutations, hematologic relapse occurred after a median of 12.9 months (range, 0.9-44.2), and BCR-ABL mutations first became detectable at a median of 5.8 months (range, 0-30.5) after starting imatinib therapy (p<0.0001). Nine patients showed evidence of BCR-ABL mutations prior to imatinib therapy (T315I, n=4; M351T, n=3; M244V and Y253H, n=1 each).

CONCLUSIONS

We conclude that: (i) D-HPLC is a sensitive method for screening for BCR-ABL mutations before and during therapy with tyrosine kinase inhibitors; (ii) the occurrence of BCR-ABL mutations during imatinib therapy is predictive of relapse; (iii) mutations may be detectable several months before relapse, and (iv) the sensitive detection of small numbers of mutated clones could provide clinical benefit by triggering early therapeutic interventions.

Imatinib as a treatment option for systemic non-Langerhans cell histiocytoses

BACKGROUND

Systemic non-Langerhans cell histiocytoses are disorders characterized by the accumulation of histiocytes that do not meet the criteria for Langerhans cells in various organs. So far, no causative treatment is known.

OBSERVATIONS

Herein, we report the case of a 41-year-old man with Rosai-Dorfman disease, a form of systemic non-Langerhans cell histiocytoses, with histiocytic infiltrations in the skin, bone marrow, liver, and spleen. Histiocytes were positive for the imatinib target proteins platelet-derived growth factor receptor beta and KIT. The disease completely responded to treatment with 400 to 600 mg daily of imatinib for more than 7 months.

CONCLUSION

This case shows that imatinib is a powerful treatment option for patients with non-Langerhans cell histiocytoses.

Expression of the p210BCR-ABL oncoprotein drives centrosomal hypertrophy and clonal evolution in human U937 cells

Centrosomes play fundamental roles in mitotic spindle organization, chromosome segregation and maintenance of genetic stability. Recently, we have shown that centrosome aberrations occur early in chronic myeloid leukemia (CML) and are induced by imatinib in normal fibroblasts in vitro. To investigate the influence of BCR-ABL on centrosomes, we performed long-term in vitro experiments employing the conditionally p210BCR-ABL-expressing (tetracycline-inducible promoter) human monocytic cell line U937p210BCR-ABL/c6 as a model of CML chronic phase. Centrosome hypertrophy was detectable after 4 weeks of transgene expression onset, increasing up to a rate of 25.7% aberrant cells within 13 weeks of propagation. This concurred with clonal expansion of aneuploid cells displaying a hyperdiploid phenotype with 57 chromosomes. Partial reversibility of centrosome aberrations (26-8%) was achieved under prolonged propagation (14 weeks) after abortion of induction and bcr-abl silencing using small interfering RNA. Therapeutic doses of imatinib did not revert the aberrant phenotype, but counteracted the observed reverting effect of bcr-abl gene expression switch off. Suggesting a mechanistic model that features distinct abl-related tyrosine kinase activity levels as essential determinants of centrosomal integrity, this is the first report mechanistically linking p210BCR-ABL oncoprotein activity to centrosomal hypertrophy.

Efficacy of dasatinib in chronic phase chronic myelogenous leukemia patients after imatinib failure according to baseline BCR- ABL mutations

7023

Background: Dasatinib is an oral, multi-targeted BCR-ABL and SRC kinase inhibitor with preclinical activity against 20/21 imatinib (Im) resistant BCR-ABL mutations. Clinical efficacy was demonstrated in phase I, II, and III studies in patients (pts) with chronic myelogenous leukemia (CML) in all phases of the disease and BCR-ABL positive acute lymphoblastic leukemia (ALL). We sought to establish a relationship between type of BCR-ABL mutations associated with Im resistance and efficacy of dasatinib in chronic phase (CP) CML pts. Methods: Between 10/03 and 03/06, dasatinib was commenced in 1,093 CP-CML pts recruited for three consecutive trials and administered for a median of 8.7 months (range <1–25.9). BCR-ABL mRNA was screened for mutations of amino acids 207–517 by D-HPLC and/or regular sequencing and data are available from 961 cases (88%). ABL polymorphisms K247R and E499E were excluded from analysis. Results: Prior to dasatinib, 75 different BCR-ABL mutations involving 56 amino acids were detected in 18/240 Im intolerant (7.5%) and 324/721 (45%) Im resistant pts. 267 pts showed one, 53 pts two, 16 pts three, and six pts four mutations. In Im resistant pts, response was not different between 370 pts with and 351 pts without baseline mutations: Complete hematologic response (CHR) was achieved in 89% vs 92%; major cytogenetic response (MCR) in 48% vs 52% being complete (CCR) in 38 vs 36%, respectively. Response dynamics were associated with preclinical activity of dasatinib: classifying mutations for IC50 values <2, 2–20 and >1,000nM (T315I), CHR was achieved in 93, 85 and 28%; MCR in 48, 42 and 0%; and CCR in 37, 35 and 0% of cases, respectively. During follow up, new mutations were detected in 30 cases, predominantly T315I (n=10), Y253H/F (n=4), and F317L (n=3). Conclusions: We conclude that dasatinib is capable of inducing hematologic and cytogenetic remissions in a significant proportion of Im resistant pts associated with BCR-ABL mutations, except T315I, but also in pts with BCR-ABL independent causes of resistance. Quality of response depends on the individual type of the mutation which is consistent with preclinical observations.

No significant financial relationships to disclose.

Dynamics of cytogenetic aberrations in Philadelphia chromosome positive and negative hematopoiesis during dasatinib therapy of chronic myeloid leukemia patients after imatinib failure

Clonal cytogenetic aberrations of the Philadelphia chromosome (Ph) positive hematopoiesis have been associated with the natural evolution of chronic myeloid leukemia (CML) to advanced disease. Clonal aberrations of Ph negative metaphases have been described after treatment with interferon or imatinib. This study evaluates the effect of dasatinib on Ph positive clones with additional cytogenetic aberrations and the frequency of novel aberrations in Ph positive and negative metaphases. Seventy-one patients treated with dasatinib after imatinib failure for a median of nine months were evaluated. Novel aberrations within Ph positive and negative clones appeared in six and three patients, respectively.

Recurrent finding of the FIP1L1-PDGFRA fusion gene in eosinophilia-associated acute myeloid leukemia and lymphoblastic T-cell lymphoma

The FIP1L1-PDGFRA fusion gene has been described in patients with eosinophilia-associated myeloproliferative disorders (Eos-MPD). Here, we report on seven FIP1L1-PDGFRA-positive patients who presented with acute myeloid leukemia (AML, n=5) or lymphoblastic T-cell non-Hodgkin-lymphoma (n=2) in conjunction with AML or Eos-MPD. All patients were male, the median age was 58 years (range, 40-66). AML patients were negative for common mutations of FLT3, NRAS, NPM1, KIT, MLL and JAK2; one patient revealed a splice mutation of RUNX1 exon 7. Patients were treated with imatinib (100 mg, n=5; 400 mg, n=2) either as monotherapy (n=2), as maintenance treatment after intensive chemotherapy (n=3) or in overt relapse 43 and 72 months, respectively, after primary diagnosis and treatment of FIP1L1-PDGFRA-positive disease (n=2). All patients are alive, disease-free and in complete hematologic and complete molecular remission after a median time of 20 months (range, 9-36) on imatinib. The median time to achievement of complete molecular remission was 6 months (range, 1-14). We conclude that all eosinophilia-associated hematological malignancies should be screened for the presence of the FIP1L1-PDGFRA fusion gene as they are excellent candidates for treatment with tyrosine kinase inhibitors even if they present with an aggressive phenotype such as AML.

Low-dose imatinib mesylate leads to rapid induction of major molecular responses and achievement of complete molecular remission in FIP1L1-PDGFRA-positive chronic eosinophilic leukemia

The FIP1L1-PDGFRA fusion gene is a recurrent molecular lesion in eosinophilia-associated myeloproliferative disorders, predicting a favorable response to imatinib mesylate. To investigate its prevalence, 376 patients with persistent unexplained hypereosinophilia were screened by the United Kingdom reference laboratory, revealing 40 positive cases (11%). To determine response kinetics following imatinib, real-time quantitative-polymerase chain reaction (RQ-PCR) assays were developed and evaluated in samples accrued from across the European LeukemiaNet. The FIP1L1-PDGFRA fusion transcript was detected at a sensitivity of 1 in 10(5) in serial dilution of the EOL-1 cell line. Normalized FIP1L1-PDGFRA transcript levels in patient samples prior to imatinib varied by almost 3 logs. Serial monitoring was undertaken in patients with a high level of FIP1L1-PDGFRA expression prior to initiation of imatinib (100 mg/d-400 mg/d). Overall, 11 of 11 evaluable patients achieved at least a 3-log reduction in FIP1L1-PDGFRA fusion transcripts relative to the pretreatment level within 12 months, with achievement of molecular remission in 9 of 11 (assay sensitivities 1 in 10(3)-10(5)). In 2 patients, withdrawal of imatinib was followed by a rapid rise in FIP1L1-PDGFRA transcript levels. Overall, these data are consistent with the exquisite sensitivity of the FIP1L1-PDGFRalpha fusion to imatinib, as compared with BCR-ABL, and underline the importance of RQ-PCR monitoring to guide management using molecularly targeted therapies.

Resistance to Targeted Therapy in Chronic Myelogenous Leukemia

The advent of the Bcr-Abl selective tyrosine kinase inhibitor imatinib mesylate (Glivec, Gleevec, Novartis, East Hanover, NJ) has substantially changed the treatment landscape for chronic myelogenous leukemia (CML). However, some patients, primarily those with advanced disease, are either initially refractory to imatinib or eventually develop imatinib resistance. Imatinib resistance or intolerance frequently depends on the re-emergence of Bcr-Abl kinase activity, but can also indicate Bcr-Abl-independent disease progression. Results from phase II/III trials suggest rates of resistance and relapse correlate with stage of disease and with the monitoring parameters: hematologic, cytogenetic, and molecular responses. To date, more than 40 different point mutations that code for distinct single amino acid substitutions in the Bcr-Abl kinase domain have been isolated from imatinib-resistant patients. These mutations affect amino acids involved in imatinib binding or in regulatory regions of the Bcr-Abl kinase domain, resulting in decreased sensitivity to imatinib while retaining aberrant kinase activity. Early mutation detection may aid in risk stratification and molecular-based treatment decisions. To overcome imatinib-resistant disease, novel tyrosine kinase inhibitors with activity against imatinib-resistant mutations and/or with inhibition of alternative pathways, such as Src activation, have recently been developed. Additional strategies include imatinib dose escalation, combination therapy, and treatment interruption to stop clonal selection of resistant cells.

Dasatinib induces complete hematologic and cytogenetic responses in patients with imatinib-resistant or -intolerant chronic myeloid leukemia in blast crisis

The prognosis for patients with chronic myeloid leukemia (CML) in myeloid blast crisis (MBC) or lymphoid blast crisis (LBC) remains poor. Although imatinib can induce responses in a subset of these patients, resistance to the drug develops rapidly. Dasatinib is a novel, oral, multitargeted kinase inhibitor of BCR-ABL and SRC family kinases. After promising phase 1 results, we report the results of phase 2 clinical trials of dasatinib in patients with imatinib-resistant or -intolerant blast crisis CML (MBC, n = 74; LBC, n = 42). At the 8-month follow-up, dasatinib induced major hematologic responses (MaHRs) in 34% and 31% of MBC- and LBC-CML patients and major cytogenetic responses (MCyRs) in 31% and 50% of these patients, respectively. Most (86%) of these MCyRs were complete cytogenetic responses (CCyRs). Responses were rapid and durable: 88% and 46%, respectively, of MBC- and LBC-CML patients achieving MaHR had not experienced disease progression at the 8-month follow-up. Response rates were similar in patients with and without BCR-ABL mutations known to confer resistance to imatinib. Dasatinib was well tolerated. Nonhematologic adverse events were mild to moderate. Cytopenias were common and could be managed by dose modification. Dasatinib is highly active and produces hematologic and cytogenetic responses in a significant number of patients with imatinib-resistant or -intolerant MBC- and LBC-CML. These trials were registered at www.clinicaltrials.gov as #CA180006 and #CA180015.

Adaptive secretion of granulocyte-macrophage colony-stimulating factor (GM-CSF) mediates imatinib and nilotinib resistance in BCR/ABL+ progenitors via JAK-2/STAT-5 pathway activation

Overcoming imatinib mesylate (IM) resistance and disease persistence in patients with chronic myeloid leukemia (CML) is of considerable importance to the issue of potential cure. Here we asked whether autocrine signaling contributes to survival of BCR/ABL+ cells in the presence of IM and nilotinib (NI; AMN107), a novel, more selective Abl inhibitor. Conditioned media (CM) of IM-resistant LAMA84 cell clones (R-CM) was found to substantially protect IM-naive LAMA cells and primary CML progenitors from IM- or NI-induced cell death. This was due to an increased secretion of the granulocyte-macrophage colony-stimulating factor (GM-CSF), which was identified as the causative factor mediating IM resistance in R-CM. GM-CSF elicited IM and NI drug resistance via a BCR/ABL-independent activation of the janus kinases 2 (JAK-2)/signal transducer and activator of transcription 5 (STAT-5) signaling pathway in GM-CSF receptor α receptor (CD116)–expressing cells, including primary CD34+/CD116+ GM progenitors (GMPs). Elevated mRNA and protein levels of GM-CSF were detected in IM-resistant patient samples, suggesting a contribution of GM-CSF secretion for IM and NI resistance in vivo. Importantly, inhibition of JAK-2 with AG490 abrogated GM-CSF–mediated STAT-5 phosphorylation and NI resistance in vitro. Together, adaptive autocrine secretion of GM-CSF mediates BCR/ABL-independent IM and NI resistance via activation of the antiapoptotic JAK-2/STAT-5 pathway. Inhibition of JAK-2 overcomes GM-CSF–induced IM and NI progenitor cell resistance, providing a rationale for the application of JAK-2 inhibitors to eradicate residual disease in CML.

Transient response to imatinib in a chronic eosinophilic leukemia associated with ins(9;4)(q33;q12q25) and a CDK5RAP2-PDGFRA fusion gene

Chronic myeloproliferative disorders with rearrangements of the platelet-derived growth factor receptor A (PDGFRA) gene at chromosome band 4q12 have shown excellent responses to targeted therapy with imatinib. Here we report a female patient who presented with advanced phase of a chronic eosinophilic leukemia. Cytogenetic analysis revealed an ins(9;4)(q33;q12q25) in 5 of 21 metaphases. FISH analysis with flanking BAC probes indicated that PDGFRA was disrupted. A novel mRNA in-frame fusion between exon 13 of the CDK5 regulatory subunit associated protein 2 (CDK5RAP2) gene, a 40-bp insert that was partially derived from an inverted sequence stretch of PDGFRA intron 9, and a truncated PDGFRA exon 12 was identified by 5'-RACE-PCR. CDK5RAP2 encodes a protein that is believed to be involved in centrosomal regulation. The predicted CDK5RAP2-PDGFRA protein consists of 1,003 amino acids and retains both tyrosine kinase domains of PDGFRA and several potential dimerization domains of CDK5RAP2. Despite achieving complete cytogenetic and molecular remission on imatinib, the patient relapsed with imatinib-resistant acute myeloid leukemia that was characterized by a normal karyotype, absence of detectable CDK5RAP2-PDGFRA mRNA, and a newly acquired G12D NRAS mutation.

Dasatinib in patients with chronic phase chronic myeloid leukemia (CP-CML) who are resistant or intolerant to imatinib: Results of the CA180013 ’START-C’ Study

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Background: Dasatinib (BMS-354825) is a novel, oral, multi-targeted kinase inhibitor of BCR-ABL and SRC kinases with proven preclinical and clinical activity against imatinib resistant BCR-ABL mutations. Methods: CA180013 is an open-label Phase II study of dasatinib in imatinib-resistant (IM-R) or -intolerant (IM-I) patients (pts) with CP-CML. Between February-August 2005, 424 pts were recruited from 75 centers worldwide. Dasatinib was given at 70 mg twice daily (BID) with dose escalation to 90 mg BID in pts lacking response, and dose reductions to 50 and 40 mg BID for toxicity. Evaluations were weekly blood counts for the first 12 weeks; bone marrow cytology and cytogenetics every 3 months. The primary endpoint was rate of major cytogenetic response (MCyR; ≤35% Philadelphia pos. metaphases) in IM-R pts. Results: Data are currently available from the first 186 pts (127 IM-R, 59 IM-I) accrued prior to May 12, 2005. Median age was 59 yrs (range 24–79); 46% were male. Median time from diagnosis of CML was 64 months. Of the IM-R pts, 72% received IM >3 yrs, and 72% had >600 mg/day of IM. Overall, 70% had received prior interferon alpha. 62 (33%) pts achieved a prior MCyR to IM. With ≥6 months of follow up, 168 (90%) pts had a complete hematologic response (CHR). MCyR were achieved in 83 (45%) pts including 40 (31%) of IM-R pts, and 43 (73%) of IM-I pts. Mutations in the BCR-ABL domain were found in 65/176 (37%) pts; 57 (88%) achieved CHR, and 24 (37%) MCyR. Molecular response analysis is ongoing. 160 (86%) pts remain on study without progression. Grade 3/4 neutropenia or thrombocytopenia was reported in 83 (45%) pts and 85 (46%) pts with onset after 4–8 weeks of therapy in most pts. Temporary dose interruptions occurred in 146 (78%), and dose reductions in 96 (52%) pts with a median daily of 108 (range 19–169) mg. Non-hematologic toxicity consisted mainly of Grade 1/2 diarrhea, headache, superficial edema, and pleural effusion, with ≤2% Grade 3/4. There was no cross-intolerance between dasatinib and IM. Conclusions: Dasatinib demonstrated substantial hematologic and cytogenetic activity in IM-R and IM-I pts with CP-CML. An updated analysis of 424 pts with ≥6 months of follow up will be presented.

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Acoustic energy: a new transfection method for cancer of the prostate, cancer of the bladder and benign kidney cells

BACKGROUND

Clinical use of gene therapy is limited by the poor efficacy and accuracy of intracellular DNA delivery. Known concepts of DNA transfection have not yet become clinical routine in the treatment of human disorders. We therefore focused on new transfection methods using different forms of acoustic energy as potentially safe and topographically applicable methods for gene delivery in the field of urology.

MATERIALS AND METHODS

Three different cell lines (prostatic and urothelial cancer, benign kidney) were transfected by different forms of acoustic energy. The effect of several parameters of electromagnetic shock wave treatment (number and frequency of impulses, energy flow density and plasmid concentration) as well as focused ultrasound on the transfection rate was assessed in a standardized experimental setup. The transfection rate was measured through reporter genes (pEGFP) by FACScan. Transfection by lipofectamine and electroporation served as positive controls.

RESULTS

All cell lines were transfectable by acoustic energy. Maximum transfection rate was achieved using focused ultrasound (49.5o%; 200 W, 500 ms, 200 microg/ml DNA). 31.3% of kidney cells were transfected by electromagnetic shock waves (1500 impulses, 200 microg/ml DNA, 0.5 mJ/mm2 energy density, 2 Hz). Plasmid strand breaks were identified as a limiting factor of the transfection rate.

CONCLUSION

Transfection by acoustic energy, especially focused ultrasound, can be achieved at a high level in different cell lines. The possible topical application to urological organs and the low level of side-effects make acoustic energy a promising new gene therapy treatment option in urology.

Prostate cancer transfection by acoustic energy using pEGFP-N1 as reporter gene in the solid Dunning R-3327-MatLu tumor

BACKGROUND

Gene therapy is expected to play a major role in medical treatment in the future. Several different methods for DNA transfection exist. We evaluated the efficacy and effects of transfection by acoustic energy in a standardized prostate cancer model.

METHODS

Subcutaneous implantation of Dunning tumors was followed by injection of pEGFP-DNA plasmid. Tumors were treated by acoustic energy with different parameter settings and the transfection rate was assessed by FACScan.

RESULTS

Standardized experimental conditions resulted in minor intragroup deviations. Intratumoral injection resulted in a transfection rate of 0.3% (control group). The statistically significant increase of 4.6% in cell transfection rate was gained by applying acoustic energy.

CONCLUSIONS

DNA transfection of solid tumors can be mediated by the application of acoustic energy. Achieved transfection rates are encouraging and imply therapeutical levels. Prodrug activation or suicide gene therapy are possible fields of investigation in the treatment of prostate cancer.