Abstract 6235: BCL2 blockade in refractory and relapsed classic Hodgkin Lymphoma; Venetoclax sensitize cells to first line treatment

Classic Hodgkin Lymphoma (cHL) is a germinal center derived lymphoma with 9,000 new cases diagnosed each year in the US. Despite 70-80% early stage cHL patients respond to current systemic treatment, 10% of patients are refractory to first-line therapy and 30-40% relapse. Refractory and relapsed disease is currently the challenge when treating cHL patients. There are no biomarkers suitable to identify patients that would be refractory or that could relapse at the primary diagnosis. Furthermore, there is no specific therapy rather than rescue chemotherapy schemes, which fails in 50% of the cases and associates with high risk severe toxicity. This highlights the need to deeper understand the cHL molecular biology and the screening for prognosis biomarkers and therapeutic innovative approaches.

We have previously reported that the alternative NFkB pathway, mediated by Rel-B and NIK (NFkB Inducing Kinase), plays an important role in cHL survival. Its constitutive activation sustains high BCL2 expression.

We analyzed NIK and BCL2 citoplasm expression in Hodgkin Reed-Sternberg cells (HRS) in the lymph node biopsies of 112 cHL naïve of therapy patients by immunohistochemistry [51 female Md age and (range) 36 (6-88), 61 male 40.7 (9-78)]. The median follow-up period was 512, months (6 to 136 months).

The univariate analysis showed no correlation between NIK or BCL2 expression and the prognosis clinical and pathological parameters, including the PET Scan indicated at the end of the first-line treatment, neither the molecular markers routinely assayed. The statistical significance was maintained in multivariate analysis (Logistic and Cox Regression p=0.01).

The survival analysis, using the Kaplan-Meir curves, showed that patients with ≥60% positive HRS cells had a shorter disease-free survival (DFS) [Log Rank Test (Mantel Cox) p=0.002] and a reduced overall survival (OS) [Log Rank Test (Mantel Cox) p=0.02]. NIK expression did not correlate with prognosis.

L1236, U-H01, KM-H2, SUPDH1 and L540 human cHL cell lines that express BCL2 protein, were sensitive to venetoclax a specific BCL2 inhibitor. The drug induced cell cycle arrest in S-Phase and G2-M when treated with 1uM each 24 hours during 10 days, as compared to wild type cells and cells treated with the vehicle. Furthermore, venetoclax sensitized cHL cell lines to vincristine and doxorubicin, two drugs used in the first-line chemotherapy scheme ABVD (Adriamycin, Bleomycin, vincristine, doxorubicin).

In summary, we found that the alternative NFkB pathway plays an important role in the refractory and relapsed Hodgkin disease biology, being BCL2 a key downstream target. BCL2 performed well as a prognosis biomarker identifying refractory patients and those that relapsed being assayed at diagnosis of the primary disease. We believe BCL2 directed-therapy in cHL could be interested in

patients that express this protein in ≥60% HRS cells in the lymph node biopsy performed at diagnosis. Furthermore venetoclax sensitized cHL cells to conventional chemotherapy.

Citation Format: Angélica M. Cedeño-Gamboa, Mariángeles Díaz, Victoria Otero, Natalia Schutz, Dorotea Fantl, Federico Jauk, Myriam Nuñez, Stella M. Ranuncolo. BCL2 blockade in refractory and relapsed classic Hodgkin Lymphoma; Venetoclax sensitize cells to first line treatment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6235.

Circulating Fibroblast Growth Factor 21 (Fgf21) as Diagnostic and Prognostic Biomarker in Renal Cancer

Background

The finding of new biomarkers is needed to have a better sub-classification of primary renal tumors (RCC) as well as more reliable predictors of outcome and therapy response. In this study, we evaluated the role of circulating FGF21, an endocrine factor, as a diagnostic and prognostic biomarker for ccRCC.

Materials and Methods

Serum samples from healthy controls (HC), clear cell and chromophobe RCC cancer patients were obtained from the serum biobank “Biobanco Público de Muestras Séricas Oncológicas” (BPMSO) of the “Instituto de Oncología “Ángel H. Roffo”. Serum FGF21 and leptin were measured by ELISA while other metabolic markers were measured following routinely clinical procedures.

Results

One of our major findings was that FGF21 levels were significantly increased in ccRCC patients compared with HC. Moreover, we showed an association between the increased serum FGF21 levels and the shorter disease free survival in a cohort of 98 ccRCC patients, after adjustment for other predictors of outcome.

Conclusion

Our results suggest that higher FGF21 serum level is an independent prognostic biomarker, associated with worse free-disease survival.

Hodgkin lymphoma requires stabilized NIK and constitutive RelB expression for survival

We have analyzed the role of the REL family members in Hodgkin lymphoma (HL). shRNA targeting of each REL member showed that HL was uniquely dependent on relB, in contrast to several other B-cell lymphomas. In addition, relA and c-rel shRNA expression also decreased HL cell viability. In exploring relB activation further, we found stable NF-κB inducing kinase (NIK) protein in several HL cell lines and that NIK shRNA also affected HL cell line viability. More importantly, 49 of 50 HL patient biopsies showed stable NIK protein, indicating that NIK and the noncanonical pathway are very prevalent in HL. Lastly, we have used a NIK inhibitor that reduced HL but not other B-cell lymphoma cell viability. These data show that HL is uniquely dependent on relB and that the noncanonical pathway can be a therapeutic target for HL. Furthermore, these results show that multiple REL family members participate in the maintenance of a HL phenotype.

Evidence of the involvement of O-GlcNAc-modified human RNA polymerase II CTD in transcription in vitro and in vivo

The RNA polymerase II C-terminal domain (CTD), which serves as a scaffold to recruit machinery involved in transcription, is modified post-translationally. Although the O-GlcNAc modification of RNA polymerase II CTD was documented in 1993, its functional significance remained obscure. We show that O-GlcNAc transferase (OGT) modified CTD serine residues 5 and 7. Drug inhibition of OGT and OGA (N-acetylglucosaminidase) blocked transcription during preinitiation complex assembly. Polymerase II and OGT co-immunoprecipitated, and OGT is a component of the preinitiation complex. OGT shRNA experiments showed that reduction of OGT causes a reduction in transcription and RNA polymerase II occupancy at several B-cell promoters. These data suggest that the cycling of O-GlcNAc on and off of polymerase II occurs during assembly of the preinitiation complex. Our results define unexpected roles for both the CTD and O-GlcNAc in the regulation of transcription initiation in higher eukaryotes.

Abstract LB-281: Hodgkin Lymphoma requires stabilized NIK and constitutive RelB expression for survival

The REL family of transcription factors plays major roles in diverse cell processes and tumor etiology. Despite considerable evidence supporting the role of the REL members in the immune system and lymphomagenesis, it is not clear whether each REL controls unique targets in distinct subsets of B cell-derived lymphomas or whether each is redundant. We delivered specific shRNAs to knock down each REL member in representative non-Hodgkin (NHL) and Hodgkin lymphoma (HL) cell lines. All NHL and HL cell lines were dependent on RelA and c-Rel for survival but only HL cells were sensitive to RelB depletion. ChIP-seq analysis uncovered an extensive nonoverlapping REL networks and that RelB directly controlled cell cycle regulators and apoptosis inhibitors including BCL2 and BCLx. However, the RelB shRNA in HL cells does not kill these cells by apoptosis. Electron microscopy revealed intact nuclei with considerable numbers of cytosolic vacuoles, indicative of autophagy. Secondly, ATG7, a key player in the autophagosomes development, is induced. We found that HL cell lines and primary tumors stably expressed NIK and that HL cell lines are missing either TRAF2 or TRAF3 protein (negative regulators of NIK). Unexpectedly, RelB shRNA resulted in the re-expression of TRAF2 and degradation of NIK protein. Lastly, both NIK shRNA and a small molecule inhibitor of NIK had the same phenotype as the relB shRNA. These data shed light on unexplored aspects of HL biology. We found that HL is the only GC B-cell derived malignancy that relies on RelB for viability, and thus differentiates Hodgkin lymphoma from non-Hodgkin lymphomas. These data argue that each REL member has specific and unique functions and gene targets, as we predicted from the lack of similarities in their transactivation domains. Furthermore, the RelB dependency in HL suggests that NIK is an attractive therapeutic target and the possibility of targeting NIK enzymatic activity in HL patients with diminishing side effects.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-281. doi:1538-7445.AM2012-LB-281

Abstract 3898: Octamer Binding Protein-2 (Oct-2): A non-oncogene addiction in germinal center derived lymphomas and a promising therapeutic target

To identify genes required for the proliferation and survival of Diffuse Large B Cell Lymphomas (DLBCL) we conducted an “Achilles Heel” RNA interference screen in cell lines model of ABC (Activated B Cell-like) and GCB (Germinal Center B-cell like) DLBCL subtypes. One of the most toxic shRNAs in this screen targeted Oct2, encoding a POU domain transcriptional activator, primarily lymphoid restricted. It was identified due its ability to bind the DNA octamer motif (ATGCAAAT) within immunoglobulin (Ig) genes promoters. The B cell specific coactivator OCA-B interacts with Oct-2 enhancing its transactivation potential. Although Oct2 and OCA-B are dipensable for Ig transcription, they are essential for germinal center (GC) development. To understand the apoptotic cell death of DLBCL cells following shRNA Oct2 induction we investigated the genetic pathways controlled by Oct2. We profiled gene expression changes in DLBCL cells upon Oct2 knocked down and merged this data with genome-wide assessment of Oct2 and OCA-B binding sites, coupling chromatin immunoprecipitation (ChiP) with high-throughput sequencing (ChIPSeq). More than 60% of the Oct2 target genes also showed OCA-B biding. The Oct2/OCA-B overlapping set of targets was enriched for genes selectively expressed in GC B cells. We found that Oct2/OCA-B lie upstream many transcription factors known to play critical roles in GC development such as BCL6, MTA3, PU.1, IRF8 and SpiB. Oct2 regulates these genes in DLBCL cells and in centroblasts. Among Oct-2 downstream effectors, BCL6 could rescue DLBCL cells from the Oct2 shRNA lethal effect. The Oct2/OCA-B binding of BCL6 promoter was confirmed by single locus ChIP in primary GC B-cells and derived lymphomas. Gel shifts experiments showed that Oct2 binds a non canonical octamer site at the BCL6 transcription start site. Our findings uncovered a novel aspect of the Oct2 biology believed to regulate the activity of octamer containing promoters. Interestingly, Oct2 controls the expression of GC specific genes that do not harbor a canonical octamer motif. By array CGH, amplification of Oct2 and OCA-B was found in less than 1% of non Hodgkin lymphoma (NHL) patient samples. Nonetheless, lymphoma cells become dependent on the Oct2 controlled network to survive, being an example of non oncogene addiction. This turns Oct2 into an attractive therapeutic target for NHL treatment. Oct2 and OCA-B lie upstream of BCL6, widely considered a master regulator of the GC response, suggesting that Oct2 directed therapy should kill the same DLBCLs as BCL6 Peptide Inhibitor. Furthermore, all GC and Post-GC B cells tested require Oct2 for survival, indicating that Oct2 directed therapy might have a broder activity spectrum than the BCL6 directed therapy. The Oct2/OCA-B binding interface would be amenable to attack with potential manageable toxicity since this interaction is exclusively required in GC B cells.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3898.

BCL6 represses CHEK1 and suppresses DNA damage pathways in normal and malignant B-cells

BCL6 is a transcriptional repressor protein that is expressed in a developmentally regulated fashion during B-cell maturation. Specifically, BCL6 is required for formation of germinal centers in response to T-cell dependent antigen activation. Germinal center B-cells feature the ability to tolerate rapid proliferation and simultaneous genetic recombination. Genetic lesions that cause constitutive expression of BCL6 are commonly associated with diffuse large B-cell lymphomas (DLBCL). Recent studies show that BCL6 contributes to the germinal center phenotype by directly repressing genes involved in sensing or responding to DNA damage including ATR, TP53 and CDKN1A. The CHEK1 protein is activated through phosphorylation by the ATR kinase domain in response to DNA damage. Activated CHEK1 can phosphorylate and modulate the activity a number of proteins including p53, providing a link between ATR sensing of DNA damage and p53 checkpoint activity. Herein we show that BCL6 can directly bind to a DNA consensus element in the CHEK1 promoter and repress its expression in normal and malignant B-cells. DLBCL cells can be killed by a specific BCL6 peptide inhibitor (BPI) that interferes with corepressor binding to the BCL6 BTB domain. BPI could reactivate CHEK1 in DLBCL cells, suggesting that its induction might contribute to BPI anti-lymphoma effects. Therefore, BCL6 can suppress multiple genes involved in a common pathway sensing, transducing and responding to genotoxic stress.

BCL6 programs lymphoma cells for survival and differentiation through distinct biochemical mechanisms

The BCL6 transcriptional repressor is the most commonly involved oncogene in diffuse large B-cell lymphomas (DLBCLs). Constitutive expression of BCL6 mediates lymphomagenesis through aberrant proliferation, survival, and differentiation blockade. Binding of BCL6 to the SMRT/N-CoR corepressors mediates the BCL6 survival effect in DLBCL. Although the basis for differentiation blockade is unknown in DLBCL, recent data suggest that BCL6 binding to the MTA3 corepressor might be involved. We report that BCL6 and MTA3 are coexpressed in normal germinal center B cells and DLBCL. Depletion of MTA3 in DLBCL cells induced a differentiation-related BCL6 target gene (PRDM1), but not target genes involved in survival. Accordingly, MTA3 and PRDM1 expression are mutually exclusive in germinal center B cells. We performed chromatin immunoprecipitation (ChIP)-on-chip mapping of the PRDM1 locus, identifying a novel BCL6 binding site on intron 3 of the PRDM1 gene, and show that BCL6 recruits MTA3 to this site. In DLBCL cells, MTA3 depletion induced plasmacytic differentiation but did not decrease viability of DLBCL cells. However, MTA3 depletion synergized with a specific BCL6 inhibitor that blocks SMRT/N-CoR binding to decrease DLBCL viability. Taken together, these results show that BCL6 regulates distinct transcriptional programs through the SMRT/N-CoR and MTA3 corepressors, respectively, and provides a basis for combinatorial therapeutic targeting of BCL6.

Prognostic value of Mdm2, p53 and p16 in patients with astrocytomas

Surgical cure of gliomas infiltrating into the brain is practically impossible and their clinical course is primarily determined by the biological behavior of the tumor cell. The purpose of this study was to analyze retrospectively prognostic input of p53, Mouse double minute-2 (Mdm2) and p16 in 103 uniformly treated patients with astrocytic tumors. The expression of these molecules was measured by immunohistochemical procedure. Prognostic evaluation was performed with the multivariate proportional hazards model. The follow-up period lasted 19 (5-122) months for the survivors. We observed that 66% of gliomas showed mutated p53, while only 17% overexpressed Mdm2, the p53-regulatory molecule. Besides, almost 50% of gliomas lost p16 immunopositivity. Only p53 labeling showed a positive correlation with the grade of malignancy, according with the WHO classification. The association between mutated p53 and histological grade remained when prognostic variables were considered in a multivariate analysis. No association between p53 status and overall survival was found. On the other hand, Mdm2 overexpression and, unexpectedly, p16 immunopositivity were associated with a shorter survival in an univariate analysis. However, Cox-regression analysis showed that only Mdm2 in female patients was an independent prognostic factor, associated with shorter survival. In conclusion, our results suggest that Mdm2 could be a relevant marker in determining the evolution of glioma patients and could provide a more objective way to classify astrocytomas.

Circulating 92-kilodalton matrix metalloproteinase (MMP-9) activity is enhanced in the euglobulin plasma fraction of head and neck squamous cell carcinoma

BACKGROUND

Cancer lethality is usually the result of local invasion and metastasis of neoplastic cells from the primary tumor. Because of their ability to degrade extracellular matrix components (EMC), matrix metalloproteinases (MMPs) have been implicated in the breakdown of basement membranes and underlying stroma, thereby facilitating tumor growth and invasion.

METHODS

The authors quantitated, by gelatin zymography and densitometric analysis, MMP activity in the euglobulin plasma fraction of 50 healthy controls and 91 head and neck squamous cell carcinoma (HNSCC) patients (51 from the larynx and 40 from the oropharynx).

RESULTS

The median value for 92-kilodalton (kD) MMP (MMP-9) activity was increased significantly in laryngeal (Md 2.1 arbitrary units (AU)/mL plasma; range, 0.2-6.4) and oropharyngeal patients (Md 2.08 AU/mL; range, 0.0-5.0) with respect to the controls (Md 0.48 AU/mL; range, 0.0-1.8). Both groups of cancer patients showed a similar behavior. Multivariate analysis indicated that circulating 92-kD MMP activity was not predicted by the clinical-pathologic parameters such as tumor stage, histologic grade, and metastatic lymph nodes. There was no association between high levels of MMP-9 activity and either cigarette smoking or alcohol consumption, major risk factors for developing HNSCC.

CONCLUSIONS

The authors found a significant increase of MMP-9 plasma activity both in laryngeal and oropharyngeal squamous cell carcinoma patients as compared with healthy controls. Further studies are necessary to establish its usefulness in the clinical management of these patients.