Defective immunogenic cell death of HMGB1-deficient tumors: compensatory therapy with TLR4 agonists

Abstract

Immunogenic cell death induced by anticancer chemotherapy is characterized by a series of molecular hallmarks that include the exodus of high-mobility group box 1 protein (HMGB1) from dying cells. HMGB1 is a nuclear nonhistone chromatin-binding protein. It is secreted at the late stages of cellular demise and engages Toll-like receptor4 (TLR4) on dendritic cells (DCs) to accelerate the processing of phagocytic cargo in the DC and to facilitate antigen presentation by DC to T cells. The absence of HMGB1 expression by dying tumor cells exposed to anthracyclines or oxaliplatin compromises DC-dependent T-cell priming by tumor-associated antigens. Here, we show that transplantable tumors exhibiting weak expression of nuclear HMGB1 respond to chemotherapy more effectively if the treatment is combined with the local or systemic administration of a highly purified and physiochemically defined and standardized lipopolysaccharide solution, which acts as a high-potency and exclusive TLR4 agonist, called Dendrophilin (DEN). The synergistic antitumor effects mediated by the combination of chemotherapy and immunotherapy relied upon the presence of the MyD88 (myeloid differentiation primary response gene) adapter of TLR4 (but not that of the TIR-domain-containing adapter-inducing interferon-b adapter), in line with the well-characterized action of DEN on the MyD88 signaling pathway. DEN and anthracyclines synergized to induce intratumoral accumulation of interferon-c-producing CD4 þ and CD8 þ T lymphocytes. Moreover, DEN could restore the immunogenicity of dying tumor cells from which HMGB1 had been depleted by RNA interference. These findings underscore the potential clinical utility of combination regimens involving immunogenic chemotherapy and certain TLR4 agonists in advanced HMGB1-deficient cancers.

Consensus guidelines for the detection of immunogenic cell death

“…Nonetheless, HMGB1-deficient malignant cells exposed to ICD inducers fail to elicit adaptive immune responses upon inoculation into immunocompetent syngeneic mice, a defect that can be corrected by the co-administration of synthetic TLR4 ligands. [225][226][227][228] Together with the notion that Tlr4 ¡/-mice fail to perceive anthracycline-treated syngeneic cells as immunogenic, 41,229 this observation demonstrates the importance of the HMGB1-TLR4 signaling axis for ICD.…”

Contribution of RIP3 and MLKL to immunogenic cell death signaling in cancer chemotherapy

“…There is indeed evidence that human cancers can lose CRT expression, which is associated with reduced T cell infiltration and poor prognosis. 46,47 Similarly, loss of HMGB1 expression is associated with cancer progression 38 and constitutes a negative prognostic marker in breast cancer treated with adjuvant chemotherapy. 48 Deficient autophagy suggested by low expression of Beclin-1 protein is also a negative prognostic marker in breast cancer 21 and in colorectal cancer.…”

“…5A, C, S5A, C), we wondered whether compensation of these ICD parameters would restore the efficacy of chemotherapy against Rip3 ¡/¡ and Mlkl ¡/¡ tumors. For this, we combined systemic MTX administration with the injection of the synthetic TLR4 ligand dendrophilin A (DENA) (which can replace HMGB1 to ligate TLR4) 38 and the apyrase inhibitor ARL67156 (ARL, which causes an elevation of extracellular ATP within the tumor). 36 DENA plus ARL failed to affect tumor growth when given without chemotherapy.…”

Killing cancer cells, twice with one shot

“…However, HMGB1 is retained tightly associated with chromatin when cells die by apoptosis. 13 Yamazaki et al 14 show here that tumors that express a low level of HMGB1 have low immunogenicity even upon ICD, but that immunogenicity can be regained if TLR4 is activated by LPS, or even better by dendrophilin, a highly purified and chemically defined form of LPS. Thus, TLR4 activation and not necessarily HMGB1 are required for ICD.…”

“…9 Two papers show that CRT exposure can be induced by IL-8 and other cytokines, 10 and that LPS/dendrophilin can replace extracellular HMGB1, 14 as they share the same TLR4 receptor (Artwork by Emilie Venereau).…”