ALBERT

Description: Recently published clinical trials have confirmed the effectiveness of anti-CD38 monoclonal antibody therapy in myeloma. Furthermore, in vitro studies of chronic lymphocytic leukaemia (CLL) cells suggest that CD38 expression can be enhanced by treatment with retinoid derivatives and thus may enhance the cytotoxic effects of anti-CD38 therapy. However, retinoids have been shown to have diverse effects on cellular function and we have previously shown that the retinoid drug acitretin upregulates CD38 expression while also reducing cell homing to the chemokine CXCL12 in primary CLL cells. To investigate possible key mechanisms for these effects, we purified CD20+ B cells from the peripheral blood of 20 CLL patients (9 previously treated, 11 untreated) and, using flow cytometry, measured percentage cell surface expression of CD38 and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4, CD152). We also measured gene expression levels of the key retinoid receptor, stimulated by retinoic acid 6 (STRA6) and it's agonist, retinol-binding protein 4 (RBP4), as well as CTLA-4, cyclin D1 (CCND1) and the transcription factors, lymphoid enhancer factor 1 (LEF1) and signal transducer and activator of transcription 3 (STAT3) using RT-PCR. GAPDH was used as a reference gene. Mean percentage surface expression of CD38 and CTLA-4 was 21.96% and 45.25% respectively. Mean ∆CT gene expression levels of CCND1, CTLA-4, LEF1 and STAT3 were 12.03, 5.57 , 5.99 and 8.98 respectively. RBP4 and STRA6 gene expression levels were undetectable in all 20 patients. Gene expression of LEF1 showed significant correlations with CTLA-4 (rs=0.572, p=0.008), CCND1 (rs=0.61, p=0.004) and STAT3 (rs=0.587, p=0.006). There was also a significant correlation between gene expression of CCND1 and of STAT3 (r =0.499, p=0.025). No significant correlations were found between percentage surface expression of CTLA-4 and gene expression levels of either CTLA-4 or of LEF1. A weak negative correlation between percentage surface expression of CTLA-4 and of CD38 was not statistically significant. Comparing untreated and previously treated patients, there was no significant difference in gene expression levels of CTLA-4 and of LEF1 or in surface expression of CTLA-4. The failure to detect RBP4 and STRA6 gene expression in unstimulated peripheral blood CLL cells is evidence against an autocrine retinoid effect in CLL, although upregulation of STRA6 gene expression following stimulation by retinoids might be anticipated. The Wnt signalling pathway has been shown to be active in CLL, including aggressive disease subtypes, highlighting the potential benefits in targeting this pathway. Intriguingly, CTLA-4 expression, although found to be the most highly induced gene following treatment with recombinant Wnt-3a in melanoma cell lines, is associated with a favourable outcome in CLL, possibly by inhibiting cell proliferation and survival. In contrast, expression of LEF1, which is a direct target of the Wnt signalling pathway, is associated with disease progression in CLL. Our finding that CTLA-4 and LEF1 gene expression levels are strongly correlated suggests that further investigation of the relationship between CTLA-4 and the Wnt/β-Catenin pathway in CLL is required and that targeting of the Wnt/β-catenin pathway may have unwanted consequences on CTLA-4 expression and function. Disclosures Quinn: Celgene: Honoraria; Janssen Cilag: Honoraria.

Description: R-CHOP chemoimmunotherapy is first line therapy for diffuse large B cell non Hodgkin lymphoma (DLBCL), although R-CHOP may be suboptimal treatment for some subtypes of DLBCL, in particular double-hit (DH) or triple-hit (TH) lymphoma. For assessment of response to chemoimmunotherapy, it has been proposed that PET-CT scan may be superior to CT scan and, in particular, demonstration of metabolic complete response (CR) by PET-CT scan at end of treatment (EOT) may be an important indicator of long term survival. However, the usefulness of follow up scans in asymptomatic patients remains debatable. We wished to assess the role of an interim CT or PET-CT scan (after 3-4 courses of chemoimmunotherapy) in predicting overall survival in patients at our centre with stage II- IV DLCBCL (Lugano Modification of Ann Arbor Classification) who received chemoimmunotherapy with curative intent. We also recorded results of scans at EOT and any further follow up scans. Between 1/7/15 and 1/7/19, 43 consecutive patients receiving R-CHOP had an interim CT or PET-CT scan. 3 of 4 patients with DH lymphoma by FISH testing changed to dose adjusted R-EPOCH after one course of R-CHOP. 39 patients had no evidence of DH, with 37 showing either partial response (PR) (N = 11) or CR (N=26) on interim CT or PET-CT scan. Of these 37 cases, one patient died of neutropenic sepsis, whilst 36 remain alive with 35 in complete remission. 30 of these 37 patients had CT scan and/or PET-CT scan at EOT: 27 were in CR, 2 were in stable PR and 1 patient (in CR on interim PET -CT scan) showed relapse on PET-CT scan. 16 patients in CR at EOT had 55 follow up surveillance scans (median 2, range 1-8) -two further relapses were detected on PET-CT scan, both 4 months after EOT. Two of the relapsed cases are in CR following further chemoimmunotherapy and allogeneic stem cell transplant whilst the other relapsed case is currently responding to further chemoimmunotherapy. 2 patients without evidence of DH showed disease progression on interim scan and were refractory to further chemotherapy, dying within 3 months and 18 months of diagnosis. All 4 patients with DH lymphoma had PR or CR at interim scan but relapsed within 5 to 8 months after diagnosis and proved chemotherapy refractory with death in 3. One patient with DH lymphoma remains in CR following local radiation and maintenance therapy with rituximab, lenalidomide and metformin. In our experience, patients with DLBCL, without DH or TH, who have evidence of response to R-CHOP at interim scan have an excellent prognosis. In this patient cohort, 85 EOT and follow up scans detected 3 relapses, suggesting that the detection rate of follow up scans in asymptomatic patients in this good prognosis group is low and of questionable usefulness. The 3 relapsed patients were readily salvageable by further chemoimmunotherapy with or without allogeneic stem cell transplant. In contrast, patients with DH lymphoma or evidence of disease progression on interim scan have very poor prognosis and urgently require alternative therapy approaches. Disclosures No relevant conflicts of interest to declare.