Evaluation of genomic imbalances and miRNA expression in patients with mycosis fungoides

FUAD HUAMÁN GARAICOA; ALEJANDRO ROISMAN; MARIANA ARIAS; CARLA TRILA; MIGUEL FRIDMANIS; ALEJANDRA ABELDAÑO; SILVIA VANZULLI; MARINA NARBAITZ; IRMA SLAVUTSKY

Viena

Congreso; 20th Congress of the European Hematology Association; 2015

European Hematology Association

Background: Mycosis fungoides (MF) is a clonally derived lymphoproliferative disorder that preferentially involves the skin, which etiology and pathogenesis remains elusive. Morphological and clinical features are not always accurate enough to predict the disease outcome. Comparative genomic hybridization and microarrays have shown imbalances of CDKN2A (p16) (9p21) and C-MYC (8q24) genes, with probable prognostic value in this pathology. In addition, miR-155 overexpression was observed in several hematological and solid tumors, promoting genomic instability, proliferation, and survival of malignant cells. Aims: In this study, we have evaluated CDKN2A losses and C-MYC gains and their association with miR-155 expression, in patients with diagnosis of MF. Results were correlated with clinicopathological features of patients. Methods: The study was performed on formalin-fixed and paraffin-embedded biopsies from 32 patients with MF (22 males; median age 62.3 years, range: 31-81 years): 28 cases showed tumor stage MF (T-MF), 13 of them in histological transformation to a large T-cell lymphoma (TR-MF) and 4 cases with folliculotropic MF (F-MF) variant. FISH analysis using OTS9P21.3 (CDKN2A) and OTS8Q24 (C-MYC) probes (LiVE-Lexel, Argentina), was performed. Gene expression was quantified by real time PCR using TaqMan Gene Expression Assays. Ten control samples from benign skin diseases were also evaluated. The study was approved by the local Ethics Committee. All individuals provided their informed written consent. Results: FISH study was performed in 26 patients, 19 (73%) showed genomic alterations (GA): 11 (42.31%) cases had 9p21 deletion (del9p21), 8 (30.77%) showed 8q24 gain (gan8q24) and 3 (11.54%) exhibited both anomalies. Del9p21 was observed in 7/13 (54%) TR-MF, 3/4 (75%) F-MF and 1/9 (11%) T-MF meanwhile gan8q24 was detected in 6/13 (46%) TR-MF and 2/4 (50%) F-MF. Thus, GA rate was: TR-MF 92%, F-MF 75% and T-MF 11% (p=0.006). These aberrations were more frequent in trunk and lower limbs (75%) in contrast with head, neck and upper limbs (25%) (p=0.012). Patients with GA showed higher CD30+ by immunohistochemistry (56.25%) and progression to histological transformation (75%) than cases with no alterations (NA) (10% and 20%, respectively) (p<0.03). Clinical response to treatment was absent in 8/16 (50%) of cases with GA vs. 1/10 (10%) patients with NA (p=0.03). Although no significant differences were reached, mean LDH (532.6 UI) and Beta 2 microglobulin levels (3.4 mg/L), median proliferation index (Ki-67) (62.86%) and extracutaneous relapse (25%) with respect to those with NA. In addition, the group with GA showed shorter overall survival (96 months) compared to cases with NA, that not reached the median survival (Log-rank p=0.04). Gene expression analysis showed miR-155 upregulation in 27% TR-MF and 50% F-MF and in only 8% T-MF. No miR-155 expression was observed in controls. The correlation with genomic imbalances found miR-155 overexpression in 33% of patients with GA and 12.5% of cases with NA. Summary/Conclusion: Our results showed higher frequency of 9p21 losses than 8q24 gains in MF patients. TR-MF exhibited the higher rate of GA, supporting a role in the process of neoplastic transformation. Although the number of FMF is reduced in our series, this morphological variant would seem to be associated to an increased frequency of genomic imbalances. Our findings on miR-155 overexpression support its relation with genomic instability and tumor development.