Combining Cell Type-Restricted Adenoviral Targeting with Immunostaining and Flow Cytometry to Identify Cells-of-Origin of Lung Cancer

On Target: An Intrapulmonary Transplantation Method for Modelling Lung Tumor Development in its Native Microenvironment

The development of in vivo lung cancer models that faithfully mimic the human disease is a crucial research tool for understanding the molecular mechanisms driving tumorigenesis. Subcutaneous transplantation assays are commonly employed, likely due to their amenability to easily monitor tumor growth and the simplistic nature of the technique to deliver tumor cells. Importantly however, subcutaneous tumors grow in a microenvironment that differs from that resident within the lung. To circumvent this limitation, here we describe the development of an intrapulmonary (iPUL) orthotopic transplantation method that enables the delivery of lung cancer cells, with precision, to the left lung lobe of recipient mice. Critically, this allows for the growth of lung cancer cells within their native microenvironment. The coupling of iPUL transplantation with position emission tomography (PET) imaging permits the serial detection of tumors in vivo and serves as a powerful tool to trace lung tumor growth and dissemination over time in mouse disease models.

Glutaminase inhibition impairs CD8 T cell activation in STK11-/Lkb1-deficient lung cancer

The tumor microenvironment (TME) contains a rich source of nutrients that sustains cell growth and facilitate tumor development. Glucose and glutamine in the TME are essential for the development and activation of effector T cells that exert antitumor function. Immunotherapy unleashes T cell antitumor function, and although many solid tumors respond well, a significant proportion of patients do not benefit. In patients with KRAS-mutant lung adenocarcinoma, KEAP1 and STK11/Lkb1 co-mutations are associated with impaired response to immunotherapy. To investigate the metabolic and immune microenvironment of KRAS-mutant lung adenocarcinoma, we generated murine models that reflect the KEAP1 and STK11/Lkb1 mutational landscape in these patients. Here, we show increased glutamate abundance in the Lkb1-deficient TME associated with CD8 T cell activation in response to anti-PD1. Combination treatment with the glutaminase inhibitor CB-839 inhibited clonal expansion and activation of CD8 T cells. Thus, glutaminase inhibition negatively impacts CD8 T cells activated by anti-PD1 immunotherapy.

Absence of pro-survival A1 has no impact on inflammatory cell survival in vivo during acute lung inflammation and peritonitis

Inflammation is a natural defence mechanism of the body to protect against pathogens. It is induced by immune cells, such as macrophages and neutrophils, which are rapidly recruited to the site of infection, mediating host defence. The processes for eliminating inflammatory cells after pathogen clearance are critical in preventing sustained inflammation, which can instigate diverse pathologies. During chronic inflammation, the excessive and uncontrollable activity of the immune system can cause extensive tissue damage. New therapies aimed at preventing this over-activity of the immune system could have major clinical benefits. Here, we investigated the role of the pro-survival Bcl-2 family member A1 in the survival of inflammatory cells under normal and inflammatory conditions using murine models of lung and peritoneal inflammation. Despite the robust upregulation of A1 protein levels in wild-type cells upon induction of inflammation, the survival of inflammatory cells was not impacted in A1-deficient mice compared to wild-type controls. These findings indicate that A1 does not play a major role in immune cell homoeostasis during inflammation and therefore does not constitute an attractive therapeutic target for such morbidities.

Consequences of Zmat3 loss in c-MYC- and mutant KRAS-driven tumorigenesis

TP53 is a critical tumor suppressor that is mutated in approximately 50% of human cancers. Unveiling the downstream target genes of TP53 that fulfill its tumor suppressor function is an area of intense investigation. Zmat3 (also known as Wig-1 or PAG608) is one such downstream target of p53, whose loss in hemopoietic stem cells lacking the apoptosis and cell cycle regulators, Puma and p21, respectively, promotes the development of leukemia. The function of Zmat3 in tumorigenesis however remains unclear. Here, to investigate which oncogenic drivers co-operate with Zmat3 loss to promote neoplastic transformation, we utilized Zmat3 knockout mice in models of c-MYC-driven lymphomagenesis and Kras^G12D-driven lung adenocarcinoma development. Interestingly, unlike loss of p53, Zmat3 germline loss had little impact on the rate of tumor development or severity of malignant disease upon either the c-MYC or Kras^G12D oncogenic activation. Furthermore, loss of Zmat3 failed to rescue Kras^G12D primary lung tumor cells from oncogene-induced senescence. Taken together, we conclude that in the context of c-MYC-driven lymphomagenesis or mutant Kras^G12D-driven lung adenocarcinoma development, additional co-occurring mutations are required to resolve Zmat3 tumor suppressive activity.

Distinct initiating events underpin the immune and metabolic heterogeneity of KRAS-mutant lung adenocarcinoma

The KRAS oncoprotein, a critical driver in 33% of lung adenocarcinoma (LUAD), has remained an elusive clinical target due to its perceived undruggable nature. The identification of dependencies borne through common co-occurring mutations are sought to more effectively target KRAS-mutant lung cancer. Approximately 20% of KRAS-mutant LUAD carry loss-of-function mutations in KEAP1, a negative regulator of the antioxidant response transcription factor NFE2L2/NRF2. We demonstrate that Keap1-deficient Kras^G12D lung tumors arise from a bronchiolar cell-of-origin, lacking pro-tumorigenic macrophages observed in tumors originating from alveolar cells. Keap1 loss activates the pentose phosphate pathway, inhibition of which, using 6-AN, abrogated tumor growth. These studies highlight alternative therapeutic approaches to specifically target this unique subset of KRAS-mutant LUAD cancers.

Lung adenocarcinomas frequently harbour KRAS mutations, of which a subset are characterized by co-mutation of KEAP1. Here the authors show, in mice, that Kras^G12D mutant tumours are metabolically distinct, with a bronchiolar cell-of-origin.

"Keaping" a lid on lung cancer: the Keap1-Nrf2 pathway

Lung cancer remains one of the world's deadliest cancers, with effective targeted treatment options available for only a small subset of patients. The rapid expansion of cancer genomics in recent years has provided insight into the genetic landscape of all major lung cancer subtypes and led to new discoveries on the heterogeneous biology underlying lung tumorigenesis. Interestingly, these studies have revealed a high frequency of alterations in the Kelch-like ECG-associated protein 1 (KEAP1)-Nuclear factor erythoid-2-related factor 2 (NRF2) stress response pathway, for which no targeted treatments are currently available. In this review, we describe the molecular mechanisms underlying NRF2 pathway activation in lung cancer cells, with a focus on in vivo functional studies in genetically engineered mouse models. Importantly, potential avenues and implications for therapeutic targeting of KEAP1-NRF2 pathway vulnerabilities for lung cancer patients will be highlighted.

FGFR3-TACC3 is an oncogenic fusion protein in respiratory epithelium

Structural rearrangements of the genome can drive lung tumorigenesis through the generation of fusion genes with oncogenic properties. Advanced genomic approaches have identified the presence of a genetic fusion between fibroblast growth factor receptor 3 (FGFR3) and transforming acidic coiled-coil 3 (TACC3) in non-small cell lung cancer (NSCLC), providing a novel target for FGFR inhibition. To interrogate the functional consequences of the FGFR3-TACC3 fusion in the transformation of lung epithelial cells, we generated a novel transgenic mouse model that expresses FGFR3-TACC3 concomitant with loss of the p53 tumor suppressor gene. Intra-nasal delivery of an Ad5-CMV-Cre virus promoted seromucinous glandular transformation of olfactory cells lining the nasal cavities of FGFR3-TACC3 (LSL-F3T3) mice, which was further accelerated upon loss of p53 (LSL-F3T3/p53). Surprisingly, lung tumors failed to develop in intra-nasally infected LSL-F3T3 and LSL-F3T3/p53 mice. In line with these observations, we demonstrated that intra-nasal delivery of Ad5-CMV-Cre induces widespread Cre-mediated recombination in the olfactory epithelium. Intra-tracheal delivery of Ad5-CMV-Cre into the lungs of LSL-F3T3 and LSL-F3T3/p53 mice however, resulted in the development of lung adenocarcinomas. Taken together, these findings provide in vivo evidence for an oncogenic function of FGFR3-TACC3 in respiratory epithelium.