Introduction: Although obesity is associated with adverse cancer outcomes in general, most retrospective clinical studies suggest a beneficial effect of obesity in NSCLC.Methods: Hypothesizing that this "obesity paradox" arises partly from the limitations of using body mass index (BMI) to measure obesity, we quantified adiposity using preoperative computed tomography images. This allowed the specific determination of central obesity as abdominal visceral fat area normalized to total fat area (visceral fat index [VFI]). In addition, owing to the previously reported salutary effect of metformin on high-BMI patients with lung cancer, metformin users were excluded. We then explored associations between visceral obesity and outcomes after surgical resection of stage I and II NSCLC. We also explored potential immunologic underpinnings of such association using complimentary analyses of tumor gene expression data from NSCLC tumors and the tumor transcriptome and immune microenvironment in an immunocompetent model of lung cancer with diet-induced obesity.Results: We found that in 513 patients with stage I and II NSCLC undergoing lobectomy, a high VFI is associated with decreased recurrence-free and overall survival. VFI was also inversely related to an inflammatory transcriptomic signature in NSCLC tumors, consistent with observations made in immunocompetent murine models wherein diet-induced obesity promoted cancer progression while exacerbating elements of immune suppression in the tumor niche.Conclusions: In all, this study uses multiple lines of evidence to reveal the adverse effects of visceral obesity in patients with NSCLC, which align with those found in animal models. Thus, the obesity paradox may, at least in part, be secondary to the use of BMI as a measure of obesity and the confounding effects of metformin use.

While immune checkpoint inhibitors (ICIs) have transformed the therapeutic landscape in oncology, they are effective in select subsets of patients. Efficacy may be limited by tumor-driven immune suppression, of which 1 key mechanism is the development of myeloid-derived suppressor cells (MDSCs). A fundamental gap in MDSC therapeutics is the lack of approaches that target MDSC biogenesis. We hypothesized that targeting MDSC biogenesis would mitigate MDSC burden and bolster tumor responses to ICIs. We tested a class of agents, dihydroorotate dehydrogenase (DHODH) inhibitors, that have been previously shown to restore the terminal differentiation of leukemic myeloid progenitors. DHODH inhibitors have demonstrated preclinical safety and are under clinical study for hematologic malignancies. Using mouse models of mammary cancer that elicit robust MDSC responses, we demonstrated that the DHODH inhibitor brequinar (a) suppressed MDSC production from early-stage myeloid progenitors, which was accompanied by enhanced myeloid maturation; (b) augmented the antitumor and antimetastatic activities of programmed cell death 1–based (PD-1–based) ICI therapy in ICI-resistant mammary cancer models; and (c) acted in concert with PD-1 blockade through modulation of MDSC and CD8 + T cell responses. Moreover, brequinar facilitated myeloid maturation and inhibited immune-suppressive features in human bone marrow culture systems. These findings advance the concept of MDSC differentiation therapy in immuno-oncology.

BackgroundBronchoalveolar lavage (BAL) is an underutilized tool in the search for pulmonary disease biomarkers. While leukocytes with effector and suppressor function play important roles in airway immunity and tumors, it remains unclear if frequencies and phenotypes of BAL leukocytes can be useful parameters in lung cancer studies and clinical trials. We therefore explored the utility of BAL leukocytes as a source of biomarkers interrogating the impact of smoking, a major lung cancer risk determinant, on pulmonary immunity.MethodsIn this ‘test case’ observational study, BAL samples from 119 donors undergoing lung cancer screening and biopsy procedures were evaluated by conventional and spectral flow cytometry to exemplify the comprehensive immune analyses possible with this biospecimen. Proportions of major leukocyte populations and phenotypic markers levels were found. Multivariate linear rank sum analysis considering age, sex, cancer diagnosis, and smoking status was performed.ResultsSignificantly increased frequencies of myeloid derived suppressor cells and PD-L1-expressing macrophages were found in current and former smokers compared to never smokers. While cytotoxic CD8T cells and conventional CD4 helper T cell frequencies were significantly reduced in current and former smokers, expression of immune checkpoints PD-1 and LAG-3 as well as Tregs proportions were increased. Lastly, the cellularity, viability and the stability of several immune readouts under cryostorage suggested BAL samples are useful for correlative endpoints in clinical trials.ConclusionsSmoking is associated with heightened markers of immune dysfunction, readily assayable in BAL, that may reflect a permissive environment for cancer development and progression in the airway.

The ability of CD8+ T cells to mount an anti-tumor immune response is compromised by immune suppression in the tumor microenvironment (TME). Tumor Associated Macrophages (TAMs) and Myeloid Derived Suppressor Cells (MDSCs) are a major part of this immune suppressive network. Targeting these populations remains challenging. Previously, we have reported that pharmacological and genetic blockade of p38 MAPK impeded the expansion and mobilization of monocytic and granulocytic MDSCs in mouse mammary carcinoma models. We also found that blockade of p38 or depletion of MDSCs reduced tumor growth and metastasis while enhancing the levels of CD8+ T cells in the primary tumors. In the present study, we asked whether CD8+ T cells contribute to the anti-metastatic activity of p38 inhibitor (p38i) and how p38 blockade affects the functional status of T cells and MDSCs. By using the mouse mammary carcinoma 4T1 model, we found that depletion of CD8+ T cells negated the effects of p38i on tumor growth and metastasis, indicating that CD8+ T cells contribute to the anti-tumor and anti-metastatic effects of p38 blockade. Next, we examined whether p38i exhibits a direct effect on T cells. The results of the T cell proliferation in vitro assays revealed that p38 blockade did not have a direct impact on T cell proliferation in response to αCD3/αCD28 stimulation. To determine the effect of p38 blockade on T cells in vivo, we performed single cell RNA-seq on the 4T1 tumor models treated with p38i and the 4T1 model with p38α (Mapk14) knockout (p38ko). This study revealed that p38 blockade by p38i or by inactivation of p38 in tumor cells decreased the amount of exhausted T cells and increased Th1 cells in the TME, indicating a positive effect on T cell functions. Furthermore, we observed a significant decrease in inflammatory signaling in granulocytes and monocytes upon p38 blockade. Our previous study showed that p38i did not affect generation of MDSCs in vitro in response to G-CSF & GM-CSF. To determine whether p38i alters MDSCs in vivo, we assessed MDSC gene signature in monocytic and granulocytic MDSCs isolated from spleens of tumor-bearing mice subjected to p38 blockade. This work revealed that the MDSC gene signature was reduced in both p38i and p38ko groups compared to tumor bearing mice treated with vehicle-control. These results indicated a reduction in the MDSC generation in the in vivo model. Our study revealed that blockade of p38 reduces tumor induced immune suppression and may enhance anti-tumor immune response in metastatic breast cancer. Citation Format: Priyanka Rajan, Justin Zonneville, Robert Zollo, Mackenzie Honikel, Sofija Raudins, Sean Colligan, Brian Morreale, Mohammed Alruwaili, Mohammed Alqarni, Scott Olejniczak, Joseph Barbi, Scott Abrams, Andrei Bakin. Blockade of p38 MAPK reduces the tumor-induced immune suppressive microenvironment in metastatic breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 73.

Dysregulated protein synthesis is seen in many aggressive cancers, including metastatic breast cancer. However, the specific contributions of certain translation initiation factors to in vivo disease remain undefined. This is particularly true of eIF4B, an RNA-binding protein and cofactor of the RNA helicase eIF4A and associated eIF4F cap-binding complex. While eIF4A, eIF4G, and eIF4E are well-known to contribute to the progression of many cancer types including metastatic breast cancers, the role played by eIF4B in breast cancer remains relatively unclear. We therefore explored how naturally divergent and experimentally modulated eIF4B levels impact tumor growth and progression in well- characterized murine triple negative breast cancer (TNBC) models. Surprisingly, we found that higher eIF4B levels in mouse and human breast cancers were associated with less aggressive phenotypes. shRNA-mediated eIF4B knockdown in TNBC lines failed to markedly alter proliferation and global translation in the cells in vitro and only modestly hindered their growth as primary mammary tumors growth in mice. However, eIF4B knockdown significantly enhanced invasive growth in vitro and exacerbated both tumor burden and mortality relative to nontargeting shRNA controls in a model of metastatic disease. Analysis of eIF4B levels and breast cancer patient survival reinforced a link to better outcomes. Interestingly, low eIF4B expression was also associated with more formidable immune evasion in vitro and in vivo, implicating a novel immunomodulatory role for this factor in the malignant setting that suggests a mode of action beyond its historical role as a co-activator of eIF4A/F.