39P - LOH as “the missing instability” potentially underlying the tumor immunogenicity: On the trails of a correlation between fractional allelic loss an...

Date 05 November 2016
Event ESMO Symposium on Immuno-Oncology 2016
Session Lunch and general poster viewing
Presenter Melissa Bersanelli
Citation Annals of Oncology (2016) 27 (suppl_8): viii4-viii17. 10.1093/annonc/mdw527
Authors M. Bersanelli1, L. Gnetti2, C. Azzoni2, L. Bottarelli2, D. Gasparro3, F. Leonardi3, E.M. Silini2, S. Buti3
  • 1Medical Oncology, Azienda Ospedaliera di Parma, 43126 - Parma/IT
  • 2Pathologic Anatomy, Azienda Ospedaliera di Parma, Parma/IT
  • 3Medical Oncology, Azienda Ospedaliera di Parma, Parma/IT

Abstract

Aim/Background

Microsatellite instable (MSI) phenotype characterizes tumors with high mutational load, encoding immunogenic neoantigens correlated with susceptibility to immune-checkpoint inhibitors (CKI). MSI is rare (3-4%) in renal cell carcinoma (RCC), although CKI are effective in a significant fraction of advanced tumors. We evaluated the hypothesis that loss of heterozygosity (LOH) of relevant tumor suppressor genes (TSG) might provide a measure of tumor immunogenicity, contributing as “the missing instability” to a high fractional allele loss (FAL) potentially underlying the rate of disease control obtained with CKI. We preliminary report the possible predictive value of LOH at different loci on 3p in patients with advanced RCC treated with the anti-PD-1 nivolumab.

Methods

After DNA extraction from FFPE tissues of nephrectomy specimens, LOH study was performed by PCR for the microsatellite markers D3S1481 (3p14.2, FHIT gene) and D3S1478 (3p21.3-21.2). Non-informative (NI) cases due to homozygosity were subsequently tested for D3S1621 (3p21.2, LCTSGR1 gene). MSI was assessed using two classical mononucleotide markers, BAT-25 and BAT-26.

Results

Nine RCC cases evaluable for response were analyzed. All were microsatellite stable (MSS). Five cases (45%) had LOH: 3 only at the FHIT locus (D3S1481), 2 at both D3S1481 and D3S1478 loci. All these patients with LOH of at least one 3p locus had good disease control and clinical benefit with nivolumab (2 had partial response and 3 stable disease, SD). The remaining 4 cases were negative for LOH at the informative loci: 3 of them were clearly non-responsive to nivolumab (confirmed progression disease) and one had SD.

Conclusions

These preliminary results suggest that LOH at 3p loci correlates with good disease control with nivolumab in advanced RCC patients. Our findings support the hypothesis that LOH at relevant genetic loci may provide a measure of mutational burden and of tumor immunogenicity and it could be used as predictive biomarker of response to CKI. Further analyses are planned with the aim to investigate other loci of key-TSG on 3p, 9p and 14p, evaluating the FAL index as potential more reliable predictive factor.

Clinical trial identification

N/A

Legal entity responsible for the study

University Hospital of Parma, Medical Oncology Unit

Funding

Support of the Medical Oncology Unit of the University Hospital of Parma

Disclosure

All authors have declared no conflicts of interest.