Contributions
Abstract: PB1683
Type: Publication Only
Background
Apoptotic regulation involves several actors which can have a positive and negative effect and may represent a target for personalized therapy. Nowadays, BCL-2 inhibitors have successfully passed preliminary phases of clinical experimentation, however the involvement of other essential proteins could represent a resistance mechanism to BCL-2 inhibitors and reveal novel therapeutic target in acute myeloid leukemia (AML).
Aims
Our study aim to investigate the expression of anti-apoptotic genes in AML patients and to unravel if these differential expressions are associated to genomic alterations.
Methods
We performed Human Transcriptome Array 2.0 (Affymetrix) and SNP 6.0 or Cytoscan HD Array (Affymetrix) in cohorts of 59 and 270 newly diagnosed AML, respectively. K-means clustering has been used to categorize patients in different cluster of expression. A pool of 7 healthy donors was used to normalize expression data. Survival analysises were conducted with Kaplan-Meyer method and differences in survival were assessed with Log-Rank test. Fisher exact test has been performed to evaluate significant associations on Copy Numeber Data.
Results
BCL-2, MCL-1 and BCL2L1 gene expression values in 59 AML patients allowed us to establish 5 clusters (Fig. 1a): cluster 1 with the overexpression of MCL-1, cluster 2 with low expression of all analyzed genes; cluster 3 with overexpression of BCL2L1, cluster 4 with overexpression of BCL-2 and cluster 5 with high values of expression of all 3 genes. Clusters 2 and 5 included the majority of patients (40/59, 68%). Furthermore, the 3-D Scatter Plot (Fig. 1a) showed that the patients out of the central cloud (Clusters 2-5) always presented an overexpression of one out of the three anti-apoptotic genes. Moreover, when BCL-2 level is low (Cluster 1-2-3), MCL-1 or BCL2L1 levels are high, respectively. In term of overall survival (OS), there were no statistically significant difference between Cluster 1-3-4, where one different anti-apoptotic gene is always overexpressed (Fig. 1b). Finally, analyzing the impact of BCL-2 expression on OS in a cohort of 36 young patients treated with chemotherapy, those with high expression of BCL2 gene had worse outcome (Fig. 1c, p=0.07). Subsequently, we screened a cohort of 270 AML patients for genomic copy number alterations by SNP array. We could not find significant CNA that could be rationally related to BCL-2, MCL-1 and BCL2L1 expression: BCL2 was lost in 3.7% and gained 1.1% of cases; MCL-1 was lost in 1.1% and gained in 0.37% of cases; and BCL2L1 was lost 0.37% and gained in 1.85% of patients.
Conclusion
BCL-2, MCL-1 and BCL2L1 expressions are quite balanced in AML patients. One out of the three genes is often overexpressed, confirming the key role of anti-apoptotic genes in leukemogenesis. Even though BCL-2 expression influences patients chemosensitivity, MCL-1 and BCL2L1 overexpression has been documented when BCL-2 is normally or downregulated. The overexpression of these genes can not be explained only by genomic aberrations. Finally, a combined approach should be realized to switch-off leukemic anti-apoptotic mechanisms: gene expression profile could provide a synthetic lethal instrument to choose the proper BH3-mimetic drug or combination. Further studies are needed to confirm the post-traductional context and unveil other characters of this pathway regolation.
Supported by: ELN, AIL, AIRC, project Regione-Università 2010-12 (L. Bolondi), FP7 NGS-PTL project, HARMONY project, Fondazione del Monte BO e RA project.
Session topic: 3. Acute myeloid leukemia - Biology & Translational Research
Keyword(s): Acute Myeloid Leukemia, Apoptosis, Gene expression profile, Inhibitor
Abstract: PB1683
Type: Publication Only
Background
Apoptotic regulation involves several actors which can have a positive and negative effect and may represent a target for personalized therapy. Nowadays, BCL-2 inhibitors have successfully passed preliminary phases of clinical experimentation, however the involvement of other essential proteins could represent a resistance mechanism to BCL-2 inhibitors and reveal novel therapeutic target in acute myeloid leukemia (AML).
Aims
Our study aim to investigate the expression of anti-apoptotic genes in AML patients and to unravel if these differential expressions are associated to genomic alterations.
Methods
We performed Human Transcriptome Array 2.0 (Affymetrix) and SNP 6.0 or Cytoscan HD Array (Affymetrix) in cohorts of 59 and 270 newly diagnosed AML, respectively. K-means clustering has been used to categorize patients in different cluster of expression. A pool of 7 healthy donors was used to normalize expression data. Survival analysises were conducted with Kaplan-Meyer method and differences in survival were assessed with Log-Rank test. Fisher exact test has been performed to evaluate significant associations on Copy Numeber Data.
Results
BCL-2, MCL-1 and BCL2L1 gene expression values in 59 AML patients allowed us to establish 5 clusters (Fig. 1a): cluster 1 with the overexpression of MCL-1, cluster 2 with low expression of all analyzed genes; cluster 3 with overexpression of BCL2L1, cluster 4 with overexpression of BCL-2 and cluster 5 with high values of expression of all 3 genes. Clusters 2 and 5 included the majority of patients (40/59, 68%). Furthermore, the 3-D Scatter Plot (Fig. 1a) showed that the patients out of the central cloud (Clusters 2-5) always presented an overexpression of one out of the three anti-apoptotic genes. Moreover, when BCL-2 level is low (Cluster 1-2-3), MCL-1 or BCL2L1 levels are high, respectively. In term of overall survival (OS), there were no statistically significant difference between Cluster 1-3-4, where one different anti-apoptotic gene is always overexpressed (Fig. 1b). Finally, analyzing the impact of BCL-2 expression on OS in a cohort of 36 young patients treated with chemotherapy, those with high expression of BCL2 gene had worse outcome (Fig. 1c, p=0.07). Subsequently, we screened a cohort of 270 AML patients for genomic copy number alterations by SNP array. We could not find significant CNA that could be rationally related to BCL-2, MCL-1 and BCL2L1 expression: BCL2 was lost in 3.7% and gained 1.1% of cases; MCL-1 was lost in 1.1% and gained in 0.37% of cases; and BCL2L1 was lost 0.37% and gained in 1.85% of patients.
Conclusion
BCL-2, MCL-1 and BCL2L1 expressions are quite balanced in AML patients. One out of the three genes is often overexpressed, confirming the key role of anti-apoptotic genes in leukemogenesis. Even though BCL-2 expression influences patients chemosensitivity, MCL-1 and BCL2L1 overexpression has been documented when BCL-2 is normally or downregulated. The overexpression of these genes can not be explained only by genomic aberrations. Finally, a combined approach should be realized to switch-off leukemic anti-apoptotic mechanisms: gene expression profile could provide a synthetic lethal instrument to choose the proper BH3-mimetic drug or combination. Further studies are needed to confirm the post-traductional context and unveil other characters of this pathway regolation.
Supported by: ELN, AIL, AIRC, project Regione-Università 2010-12 (L. Bolondi), FP7 NGS-PTL project, HARMONY project, Fondazione del Monte BO e RA project.
Session topic: 3. Acute myeloid leukemia - Biology & Translational Research
Keyword(s): Acute Myeloid Leukemia, Apoptosis, Gene expression profile, Inhibitor