Unexpected PD-L1 Immune Evasion mechanism in TNBC, Ovarian and other Solid Tumors by DR5 Agonists (2020)
Figure 6

Figure 6. Co-targeting of DR5 with ROCK1i or PD-L1 enhances immune infiltration, overpowers immune suppression and improves anti-tumor activity

(A) Chi-G4S-DR5 stable 4T1 tumors harboring mice were treated lexatumumab, lexatumumab +ROCK1i, and avelumab + lexatumumab and other controls as indicated. Antibodies were treated i.p at 100μg dose (6 total), ROCK1i (in PBS) was injected directly into tumors at 2mg/kg dose (6 total). Various treatments were started when tumors were ~400mm3 size. Harvested tumors were grouped together and sized matched (3 independent sets: n=2-6 tumors in each set) followed by TIL isolation (see methods). CD8/CD45 and CD4/CD45 expressing cells were measured by flow cytometry. The data shown is from a single set of experiment. For addition sets, see also appendix Fig S10 (n=3)

(B) Plots showing % of total double positive TILs (CD8+CD45+ + CD4+CD45+) in right upper quadrant after combining 3 independent experiments. Indicated treatments are shown at the bottom of bars (n=3).

(C) Ratio of CD8+CD45+/CD4+CD45+ isolated TILs from tumors in each indicated treatment (n=3).

(D) Similar to (A) Chi-G4S-DR5 stable MC38 tumors harboring mice were treated (6 total doses) lexatumumab, avelumab, ROCK1i, lexatumumab +ROCKi, and avelumab + lexatumumab and IgG1 control as indicated. Harvested tumors homogenized followed by quantitation. Protein lysates were run on SDS-Page followed by immunoblotting using indicated CD8, CD4, Foxp3, caspase-3 and granzyme-b antibody. GAPDH is loading control. Red arrows indicated cleaved caspase-3 p19 and p17 fragments. For additional Chi-G4S-DR5 stable 4T1 tumors western data, see Fig EV4E.

(E) Schematic of anti-PD-L1 (Avelumab) and anti-muDR5 (MD5-1) IgG1 antibodies. Highlighted blue area depicts avelumab's antigen binding variable domain and dark red area indicates MD5-1's antigen binding variable domain.

(F) Schematic and genetic construction of avelu-MD5-1 bispecific antibody that contains anti-PD-L1 (Avelumab), anti-muDR5 (MD5-1) heavy/light (VH/VL) variable domains (blue and dark red respectively. Both monospecific and bispecific antibodies contain LALA mutation to avoid interference with Fc-effector function. CK: C-kappa, CH1: Constant heavy chain 1, CH2: Constant heavy chain 2, CH3: Constant heavy chain 3. Dark blue dotted line under CH3 and between MD5-1 VH and VL depicts flexible linker.

(G) Working mechanism of avelu-MD5-1 bispecific antibody where surface stabilized PD-L1 acts as an anchor to enhance avidity optimized binding and clustering of DR5 receptor mediated apoptotic signaling.

(H) Cell killing assay of 4T1 cells treated with murine DR5 agonist MD5-1 and bispecific avelu-MD5 antibody.

(I) Balb/c mice harboring luciferase stable 4T1 tumors were i.p. injected with indicated antibodies. 50μg dose and mice were imaged after 5 doses.

(J) 6-8 weeks old C57BL/6 mice bearing MC38 tumors were intraperitoneally (i.p.) injected with 50μg of indicated antibody every third day (n=4-6). Indicated treatments were started when tumors were ~100mm3 size. Tumor volumes were quantified at indicated days by caliper measurements.

(K) ~150-200mm3 size MC38 tumor bearing C57LB/6 mice were treated with indicated MD5-1, avelumab and bispecific antibodies along with control IgG1, 6 total doses. Harvested tumors were homogenized followed by quantitation. Protein lysates were run on SDS-Page followed by immunoblotting using indicated CD8, CD4, caspase-3 and granzyme-b antibody. GAPDH is loading control. Red arrows indicated cleaved caspase-3 p19 and p17 fragments.

(L) 6-8 weeks old C57BL/6 mice were injected with MC38 cells. When tumors reached ~150-200mm3, animals were intraperitoneally (i.p.) injected with 50μg of indicated antibody every third day. On day 18, tumors were harvested, sized matched and pooled by treatment group, exposed to collagenase/DNase and were single cell suspensions enriched for CD8+ cells. Enriched CD8+ T-cells from various treatments were restimulated with anti-CD3 (OKT3) antibody for 4 additional hours. CD8 gated cells were next analyzed for IFN-γ intracellular expression using flow cytometry. The data shown is from a single set of experiment. See also appendix Fig S11 (n=3).

(M) Percentage of IFN-γ+CD8+ double positive cells from 3 independent experiments. For supporting flow cytometry data, see also appendix Fig S11 (n=4).

Data information: Mean ± SD. Statistical significance in (B) and (C) was determined by Mann Whitney two tailed test and in (J) using two-tailed paired Wilcoxon Mann-Whitney test. Statistical significance in (M) was determined by unpaired t test. (*p <0.05, **p <0.005)