Components of the SWI/SNF chromatin‐remodeling complex, such as INI1, are inactivated in human cancer and, thus, act as tumor suppressors. Here we screened for mutations the entire coding sequence of BRG1 (SMARCA4), which encodes the ATPase of the complex, in 59 lung cancer cell lines of the most common histopathological types. Mutations were detected in 24% of the cancer cell lines, many of them in cells commonly used for lung cancer research. All mutations were homozygous and most predicted truncated proteins. The alterations were significantly more frequent in the non‐small‐cell lung cancer (NSCLC) type (13/37, 35%) as compared to the small‐cell lung cancer (SCLC) type (1/19, 5%) (P<0.05; Fisher's Exact test) and BRG1 was the fourth most frequently altered gene in NSCLC cell lines. BRG1 mutations coexisted with mutations/deletions at KRAS, LKB1, NRAS, P16, and P53. However, alterations at BRG1 always occurred in the absence of MYC amplification, suggesting a common role in lung cancer development. In conclusion, our data strongly support that BRG1 is a bona fide tumor suppressor and a major factor in lung tumorigenesis. Hum Mutat 29(5), 617–622, 2008.

The complement system contributes to various immune and inflammatory diseases, including cancer. In this study, we investigated the capacity of lung cancer cells to activate complement and characterized the consequences of complement activation on tumor progression. We focused our study on the production and role of the anaphylatoxin C5a, a potent immune mediator generated after complement activation. We first measured the capacity of lung cancer cell lines to deposit C5 and release C5a. C5 deposition, after incubation with normal human serum, was higher in lung cancer cell lines than in nonmalignant bronchial epithelial cells. Notably, lung malignant cells produced complement C5a even in the absence of serum. We also found a significant increase of C5a in plasma from patients with non-small cell lung cancer, suggesting that the local production of C5a is followed by its systemic diffusion. The contribution of C5a to lung cancer growth in vivo was evaluated in the Lewis lung cancer model. Syngeneic tumors of 3LL cells grew slower in mice treated with an antagonist of the C5a receptor. C5a did not modify 3LL cell proliferation in vitro but induced endothelial cell chemotaxis and blood-vessels formation. C5a also contributed to the immunosuppressive microenvironment required for tumor growth. In particular, blockade of C5a receptor significantly reduced myeloid-derived suppressor cells and immunomodulators ARG1, CTLA-4, IL-6, IL-10, LAG3, and PDL1 (B7H1). In conclusion, lung cancer cells have the capacity to generate C5a, a molecule that creates a favorable tumor microenvironment for lung cancer progression.

Disruption of the programmed cell death protein 1 (PD-1) pathway with immune checkpoint inhibitors represents a major breakthrough in the treatment of non–small cell lung cancer. We hypothesized that combined inhibition of C5a/C5aR1 and PD-1 signaling may have a synergistic antitumor effect. The RMP1-14 antibody was used to block PD-1, and an L-aptamer was used to inhibit signaling of complement C5a with its receptors. Using syngeneic models of lung cancer, we demonstrate that the combination of C5a and PD-1 blockade markedly reduces tumor growth and metastasis and leads to prolonged survival. This effect is accompanied by a negative association between the frequency of CD8 T cells and myeloid-derived suppressor cells within tumors, which may result in a more complete reversal of CD8 T-cell exhaustion. Our study provides support for the clinical evaluation of anti–PD-1 and anti-C5a drugs as a novel combination therapeutic strategy for lung cancer. Significance: Using a variety of preclinical models of lung cancer, we demonstrate that the blockade of C5a results in a substantial improvement in the efficacy of anti–PD-1 antibodies against lung cancer growth and metastasis. This study provides the preclinical rationale for the combined blockade of PD-1/PD-L1 and C5a to restore antitumor immune responses, inhibit tumor cell growth, and improve outcomes of patients with lung cancer. Cancer Discov; 7(7); 694–703. ©2017 AACR. This article is highlighted in the In This Issue feature, p. 653

Reactivation of cytotoxic CD8⁺ T-cell responses has set a new direction for cancer immunotherapy. Neutralizing antibodies targeting immune checkpoint programmed cell death protein 1 (PD-1) or its ligand (PD-L1) have been particularly successful for tumor types with limited therapeutic options such as melanoma and lung cancer. However, reactivation of T cells is only one step toward tumor elimination, and a substantial fraction of patients fails to respond to these therapies. In this context, combination therapies targeting more than one of the steps of the cancer-immune cycle may provide significant benefits. To find the best combinations, it is of upmost importance to understand the interplay between cancer cells and all the components of the immune response. This review focuses on the elements of the complement system that come into play in the cancer-immunity cycle. The complement system, an essential part of innate immunity, has emerged as a major regulator of cancer immunity. Complement effectors such as C1q, anaphylatoxins C3a and C5a, and their receptors C3aR and C5aR1, have been associated with tolerogenic cell death and inhibition of antitumor T-cell responses through the recruitment and/or activation of immunosuppressive cell subpopulations such as myeloid-derived suppressor cells (MDSCs), regulatory T cells (Tregs), or M2 tumor-associated macrophages (TAMs). Evidence is provided to support the idea that complement blocks many of the effector routes associated with the cancer-immunity cycle, providing the rationale for new therapeutic combinations aimed to enhance the antitumor efficacy of anti-PD-1/PD-L1 checkpoint inhibitors.