Project description:Inactivating mutations in LKB1/STK11 are present in ~20% of non-small cell lung cancers (NSCLC) and portend poor response to anti-PD-1 immunotherapy in patients and genetically engineered mouse model (GEMMs). Here, we sought to uncover the basis for immunotherapy resistance of these tumors and to define strategies that overcome this barrier. Whereas high tumor mutational burden (TMB) often correlates with response to anti-PD1 treatment, we found that LKB1-deficient NSCLCs from non-smokers and GEMMs exhibited striking elevations in nonsynonymous mutations compared to LKB1 wildtype tumors. Correspondingly, LKB1 mutant NSCLC cell lines showed defects in both replication dependent and independent double-strand DNA break (DSB) repair, which were reversed upon LKB1 re-expression.
Project description:Inactivating mutations in LKB1/STK11 are present in ~20% of non-small cell lung cancers (NSCLC) and portend poor response to anti-PD-1 immunotherapy in patients and genetically engineered mouse model (GEMMs). Here, we sought to uncover the basis for immunotherapy resistance of these tumors and to define strategies that overcome this barrier. Whereas high tumor mutational burden (TMB) often correlates with response to anti-PD1 treatment, we found that LKB1-deficient NSCLCs from non-smokers and GEMMs exhibited striking elevations in nonsynonymous mutations compared to LKB1 wildtype tumors. Correspondingly, LKB1 mutant NSCLC cell lines showed defects in both replication dependent and independent double-strand DNA break (DSB) repair, which were reversed upon LKB1 re-expression.
Project description:Autophagy degrades and recycles intracellular components to sustain metabolism and survival during starvation. Tumor cells upregulate and require autophagy to support their metabolism and enhance their proliferation and malignancy, and host autophagy also promotes tumor growth by providing essential tumor nutrients such as arginine in the circulation or alanine in the local tumor microenvironment. In addition to its metabolic role, autophagy regulates immune cell homeostasis and function, and suppresses inflammation, which may also play a role in cancer. Although host autophagy does not promote a T cell anti-tumor immune response in tumors with low tumor mutational burden (TMB), whether this was the case in tumors with high TMB was not known. Here we show that in contrast to low TMB tumors, host-specific deletion of the essential autophagy gene Atg7 induces a pro-inflammatory cytokine response and limits the growth of high TMB tumors, which is rescued by T-cell depletion. Expression of immune-related genes is increased in tumors from Atg7Δ/Δ hosts in a T-cell dependent manner. Tumors from Atg7Δ/Δ hosts also have decreased T regulatory cells (Tregs), and depletion of Tregs phenocopies the reduced tumor growth observed in Atg7Δ/Δ hosts. Moreover, loss of Stimulator of interferon genes (Sting) or IFNg restores growth of high TMB tumors on Atg7Δ/Δ hosts. Finally, similar to whole-body loss of autophagy, specific loss of autophagy in the liver is sufficient to limit tumor growth. Thus, autophagy, especially in the liver, promotes tumor immune tolerance by limiting STING, T cells, and IFNg, which enables tumor growth. We have designated this: Hepatic Autophagy Immune Tolerance (HAIT). Autophagy thereby promotes tumor growth through both metabolic and immune mechanisms depending on mutational load, and autophagy inhibition is an effective means to promote an anti-tumor T-cell response in high TMB tumors.
Project description:Autophagy degrades and recycles intracellular components to sustain metabolism and survival during starvation. Tumor cells upregulate and require autophagy to support their metabolism and enhance their proliferation and malignancy, and host autophagy also promotes tumor growth by providing essential tumor nutrients such as arginine in the circulation or alanine in the local tumor microenvironment. In addition to its metabolic role, autophagy regulates immune cell homeostasis and function, and suppresses inflammation, which may also play a role in cancer. Although host autophagy does not promote a T cell anti-tumor immune response in tumors with low tumor mutational burden (TMB), whether this was the case in tumors with high TMB was not known. Here we show that in contrast to low TMB tumors, host-specific deletion of the essential autophagy gene Atg7 induces a pro-inflammatory cytokine response and limits the growth of high TMB tumors, which is rescued by T-cell depletion. Expression of immune-related genes is increased in tumors from Atg7Δ/Δ hosts in a T-cell dependent manner. Tumors from Atg7Δ/Δ hosts also have decreased T regulatory cells (Tregs), and depletion of Tregs phenocopies the reduced tumor growth observed in Atg7Δ/Δ hosts. Moreover, loss of Stimulator of interferon genes (Sting) or IFNg restores growth of high TMB tumors on Atg7Δ/Δ hosts. Finally, similar to whole-body loss of autophagy, specific loss of autophagy in the liver is sufficient to limit tumor growth. Thus, autophagy, especially in the liver, promotes tumor immune tolerance by limiting STING, T cells, and IFNg, which enables tumor growth. We have designated this: Hepatic Autophagy Immune Tolerance (HAIT). Autophagy thereby promotes tumor growth through both metabolic and immune mechanisms depending on mutational load, and autophagy inhibition is an effective means to promote an anti-tumor T-cell response in high TMB tumors. Genomic DNA Profiling using Agilent SureSelect Mouse All Exon kit and sequencing using Illumina NextSeq550
Project description:Inherited mutation in LKB1 results in the Peutz-Jeghers syndrome (PJS), characterized by intestinal hamartomas and a modestly increased frequency of gastrointestinal and breast cancer1. Somatic inactivation of LKB1 occurs in human lung adenocarcinoma2-4, but its tumor suppressor role in this tissue is unknown. Here we show that somatic Lkb1 deficiency strongly cooperates with somatic K-rasG12D activating mutation to accelerate the development of mouse lung tumorigenesis. Lkb1 deficiency in the setting of K-rasG12D mutation (K-ras Lkb1L/L) was associated with decreased tumor latency and increased tumor aggressiveness including metastasis. Furthermore, tumors from K-ras Lkb1L/L mice demonstrated histologies--squamous, adenosquamous and large cell--not seen with K-rasG12D mutation, Ink4a/Arf inactivation, or p53 inactivation alone or in combination. Experiments in vitro suggest that LKB1 suppresses lung tumorigenesis and progression through both p16INK4a-ARF-p53 dependent and independent mechanisms. These data indicate that LKB1 regulates lung tumor progression and differentiation. Keywords: cancer research To analyze the role of LKB1 in lung cancer progression and differentiation, we have dissected the lung tumors from mice with/without lkb1 loss and performed the microarray analyses to compare their gene expression pattern. In addition, we have also performed microarray analysis in both A549 and H2126 cell lines after reconsistitution of either wt-lkb1 or the kinase dead form of lkb1 (lkb1-KD) to confirm what we observed from in vivo studies.
Project description:LKB1 is a tumor suppressor lost in approximately 30% of lung adenocarcinomas. It is a serine-threonine kinase involved in regulating metabolism, proliferation, and cell polarity. We have characterized its association with mRNA expression profiles in resected tumors and in cell lines, but little is known about the direct effects of LKB1 on the regulation of these genes. This study investigates the effects of LKB1 activity on mRNA expression in two LKB1-mutant lung adenocarcinoma cell lines, H2122 and A549. Wild-type LKB1 has been stably expressed in these cell lines using a pBABE retrovirus as well as an empty pBABE control and a kinase-dead mutant of LKB1 (K78I) control (Addgene). Samples submitted are two cell lines, three experimental conditions, and three replicates, for a total of 17 samples (one sample was excluded for poor RNA quality). Gene expression of these samples are analyzed to determine transcriptional regulatory effects of LKB1 expression. Results of this analysis are compared to our analysis of resected human tumors to determine gene patterns that are differentially expressed between LKB1-deficient and LKB1-wild-type tumors whose expression is also affected by restoration of LKB1 in vitro. RMA gene expression was taken from two cell lines stably expressing LKB1 or controls of K78I mutant LKB1 or empty pBABE vector. Log2 average expression differences are calculated and compared to results from analysis of gene expression associated with LKB1 loss in resected human tumors.