LRRC15 Is a Novel Mesenchymal Protein and Stromal Target for Antibody-Drug Conjugates.

Progress in understanding tumor stromal biology has been constrained in part because cancer-associated fibroblasts (CAF) are a heterogeneous population with limited cell-type-specific protein markers. Using RNA expression profiling, we identified the membrane protein leucine-rich repeat containing 15 (LRRC15) as highly expressed in multiple solid tumor indications with limited normal tissue expression. LRRC15 was expressed on stromal fibroblasts in many solid tumors (e.g., breast, head and neck, lung, pancreatic) as well as directly on a subset of cancer cells of mesenchymal origin (e.g., sarcoma, melanoma, glioblastoma). LRRC15 expression was induced by TGFß on activated fibroblasts (αSMA+) and on mesenchymal stem cells. These collective findings suggested LRRC15 as a novel CAF and mesenchymal marker with utility as a therapeutic target for the treatment of cancers with LRRC15-positive stromal desmoplasia or cancers of mesenchymal origin. ABBV-085 is a monomethyl auristatin E (MMAE)-containing antibody-drug conjugate (ADC) directed against LRRC15, and it demonstrated robust preclinical efficacy against LRRC15 stromal-positive/cancer-negative, and LRRC15 cancer-positive models as a monotherapy, or in combination with standard-of-care therapies. ABBV-085's unique mechanism of action relied upon the cell-permeable properties of MMAE to preferentially kill cancer cells over LRRC15-positive CAF while also increasing immune infiltrate (e.g., F4/80+ macrophages) in the tumor microenvironment. In summary, these findings validate LRRC15 as a novel therapeutic target in multiple solid tumor indications and support the ongoing clinical development of the LRRC15-targeted ADC ABBV-085.Significance: These findings identify LRRC15 as a new marker of cancer-associated fibroblasts and cancers of mesenchymal origin and provide preclinical evidence for the efficacy of an antibody-drug conjugate targeting the tumor stroma. Cancer Res; 78(14); 4059-72. ©2018 AACR.

Effect of PF-02341066 and radiation on non-small cell lung cancer cells.

Recently, a fusion protein of echinoderm microtubule associated protein like-4 (EML4) and anaplastic lymphoma kinase (ALK) has been found in non-small cell lung cancer (NSCLC) patients. In addition, endogenous expression of phosphorylated c-Met was found to be increased in many invasive NSCLC cases. PF-02341066 (crizotinib) is a novel dual c-Met and EML4-ALK inhibitor, and preclinical studies have shown that treatment with ALK inhibitors leads to drastic tumor regression in xenograft models. A phase I trial of PF-02341066 yielded a 53% response rate and a disease control rate of 79%. We evaluated crizotinib as a potential radiation-sensitizing agent in multiple established NSCLC cell lines with varying expression levels of c-Met and EML4-ALK. The combined effect of ionizing radiation (IR) and PF-02341066 was determined by the surviving cell fraction, cell cycle distribution, apoptosis, DNA double-strand break repair in 5 NSCLC cell lines (A549, H460, H3122, H2228 and H1993) and in in vivo xenograft studies. Treatment of NSCLC cells with either PF-02341066 alone or PF-02341066 + IR did not significantly alter cellular radiosensitivity, DNA repair kinetics and cell cycle distribution; no significant enhancement of tumor growth delay was noted in response to the combined treatment of PF-02341066 + IR. EML4-ALK and c-Met inhibition leads to activation of parallel pathways that converge on Akt signaling which abrogates any radiation-sensitizing effect. Although PF-02341066 is an effective therapy able to suppress tumor growth in tumors that exhibit positivity for either EML4-ALK or c-Met, it did not affect the intrinsic radiation response of tumor cell lines. In the present study, we demonstrated that PF-02341066 did not enhance radiation sensitivity in a panel of NSCLC cell lines.