CEA expression heterogeneity and plasticity confer resistance to the CEA-targeting bispecific immunotherapy antibody cibisatamab (CEA-TCB) in patient-derived colorectal cancer organoids

Abstract

Background The T cell bispecific antibody cibisatamab (CEA-TCB) binds Carcino-Embryonic Antigen (CEA) on cancer cells and CD3 on T cells, which triggers T cell killing of cancer cell lines expressing moderate to high levels of CEA at the cell surface. Patient derived colorectal cancer organoids (PDOs) may more accurately represent patient tumors than established cell lines which potentially enables more detailed insights into mechanisms of cibisatamab resistance and sensitivity. Methods We established PDOs from multidrug-resistant metastatic CRCs. CEA expression of PDOs was determined by FACS and sensitivity to cibisatamab immunotherapy was assessed by co-culture of PDOs and allogeneic CD8 T cells. Results PDOs could be categorized into 3 groups based on CEA cell-surface expression: CEA hi ( n = 3), CEA lo ( n = 1) and CEA mixed PDOs ( n = 4), that stably maintained populations of CEA hi and CEA lo cells, which has not previously been described in CRC cell lines. CEA hi PDOs were sensitive whereas CEA lo PDOs showed resistance to cibisatamab. PDOs with mixed expression showed low sensitivity to cibisatamab, suggesting that CEA lo cells maintain cancer cell growth. Culture of FACS-sorted CEA hi and CEA lo cells from PDOs with mixed CEA expression demonstrated high plasticity of CEA expression, contributing to resistance acquisition through CEA antigen loss. RNA-sequencing revealed increased WNT/β-catenin pathway activity in CEA lo cells. Cell surface CEA expression was up-regulated by inhibitors of the WNT/β-catenin pathway. Conclusions Based on these preclinical findings, heterogeneity and plasticity of CEA expression appear to confer low cibisatamab sensitivity in PDOs, supporting further clinical evaluation of their predictive effect in CRC. Pharmacological inhibition of the WNT/β-catenin pathway may be a rational combination to sensitize CRCs to cibisatamab. Our novel PDO and T cell co-culture immunotherapy models enable pre-clinical discovery of candidate biomarkers and combination therapies that may inform and accelerate the development of immuno-oncology agents in the clinic. Electronic supplementary material The online version of this article (10.1186/s40425-019-0575-3) contains supplementary material, which is available to authorized users.

Immunopeptidomics of colorectal cancer organoids reveals a sparse HLA class I neoantigen landscape and no increase in neoantigens with interferon or MEK-inhibitor treatment

“…The establishment of the MSS CRC PDOs from the Prospect C, Prospect R (Chief investigator: D. Cunningham, UK national ethics committee approval numbers: 12/LO/0914 and 14/LO/1812, respectively) and the FOrMAT trials (Chief investigator: N. Starling, UK national ethics committee approval number 13/LO/1274) has previously been described [10]. All patients had provided written informed consent before trial inclusion.…”

“…PDOs are usually cultured in a 3D matrigel matrix which is expensive and laborious. We recently developed a method that grows PDOs attached to the surface of conventional plastic culture vessels in media supplemented with only 2% matrigel which overlays PDO cells and can be easily removed with the media [10]. Here, we show this enables large-scale expansion of PDOs to several hundred million cells, sufficient for in-depth immunopeptidomic analyses.…”

Influence of antigen density and immunosuppressive factors on tumor-targeted costimulation with antibody-fusion proteins and bispecific antibody-mediated T cell response

“…However, a heterogeneous target expression or a suboptimal prevalence of target expression in the tumor might still limit this approach. Indeed, CEA expression heterogeneity and plasticity were reported to confer resistance to cibisatamab, an optimized CEAxCD3 bispecific antibody, in patient-derived colorectal cancer organoids [23].…”

“…However, a heterogeneous target expression or a suboptimal prevalence of target expression in the tumor might still limit this approach. Indeed, CEA expression heterogeneity and plasticity were reported to confer resistance to cibisatamab, an optimized CEAxCD3 bispecific antibody, in patient-derived colorectal cancer organoids [ 23 ]. Interestingly, recent studies with CD38-directed CAR-T cells showed that low scFv affinity could be compensated by costimulation via CD28 and 4-1BB to rescue and enforce the antitumor effect, pointing out the potential of costimulation in a combinatorial design [ 24 ].…”

Combination therapy with T cell engager and PD-L1 blockade enhances the antitumor potency of T cells as predicted by a QSP model

“…Gonzalez-Exposito et al developed patient derived CRC organoids to explore the mechanism of T cell bispecific antibody cibisatamab (CEA-TCB) sensitivity. 10 Bacac et al reported the antitumor activity of CEA-TCB in 110 cell lines and the mode of CEA-TCB mediated CRC cell lysis in a mouse tumor model. 11 Waaijer et al developed a T cell-engaging bispecific antibody (BsAb) to target cell surface A33 antigen (huA33-BsAb), which is expressed in more than 95% of human colon cancers.…”