Search

Mechanisms underlying the propensity of latent lung adenocarcinoma (LUAD) to relapse are poorly understood. In this study, we show how differential expression of a network of extracellular matrix (ECM) molecules and their interacting proteins contributes to risk of relapse in distinct LUAD subtypes. Overexpression of the hyaluronan receptor HMMR in primary LUAD was associated with an inflammatory molecular signature and poor prognosis. Attenuating HMMR in LUAD cells diminished their ability to initiate lung tumors and distant metastases. HMMR upregulation was not required for dissemination in vivo, but enhanced ECM-mediated signaling, LUAD cell survival, and micrometastasis expansion in hyaluronan-rich microenvironments in the lung and brain metastatic niches. Our findings reveal an important mechanism by which disseminated cancer cells can coopt the inflammatory ECM to persist, leading to brain metastatic outgrowths. Cancer Res; 77(8); 1905–17. ©2017 AACR.

The majority of EGFR mutant lung adenocarcinomas respond well to EGFR tyrosine kinase inhibitors (TKIs). However, the majority of these responses are partial, with drug-tolerant residual disease remaining even at the time of maximal response. This residual disease serves as a reservoir for the emergence of acquired resistance and tumor relapse, which inevitably occurs in patients treated with TKIs. It is thus critical to understand the biology of residual tumor cells and find out the mechanisms that underlie drug tolerance. Knowledge of such mechanisms could lead to the identification of potential strategies to forestall the emergence of drug resistance. Studies of residual disease have been hampered by the difficulty of studying these persister cells in patient specimens, and most studies to date have relied on analysis of established cell lines in culture. To investigate the cellular and molecular properties of residual tumor cells in vivo, we leveraged patient-derived models of EGFR mutant lung cancer. Three EGFR mutant PDXs were treated with the 3rd-generation TKI osimertinib. Tumors regressed in all cases, but measurable residual tumor remained in 2 out of the 3 PDXs even after 6 weeks of osimertinib treatment. Whole-exome sequencing (WES) of the untreated PDXs compared to the residual tumors revealed an unchanged mutational landscape between the samples, indicating that genetic mechanisms did not account for drug tolerance. Bulk RNA-sequencing, however, revealed extensive transcriptional changes between the untreated PDX and residual disease. In one of the PDXs, we identified upregulation of neuroendocrine lineage transcription factor ASCL1 in residual disease compared to untreated tumors. Using single-cell RNA-sequencing, we found a pre-existing ASCL1hi tumor cell population in untreated tumors, suggesting that these cells, which possessed drug-tolerant properties, were selected for during drug treatment. Depending on the cell line examined, expression of ASCL1 in human mutant EGFR lung cancer cell lines increased the number of persister clones following osimertinib treatment, indicating that the cellular context contributed to ASCL1’s role in conferring drug tolerance. Our studies provide insights into the role of neuroendocrine factor ASCL1 as a potential driver of drug tolerance in mutant EGFR lung cancer, and ongoing work is focused on identifying the mechanistic underpinnings of these findings. Citation Format: Bomiao Hu, Fernando J. de Miguel, Zongzhi Liu, Lok-Hei Chan, Mary Ann Melnick, Qin Yan, Don Nguyen, Rong Fan, Katerina Politi. ASCL1 confers tolerance to tyrosine kinase inhibitors in EGFR mutant lung cancer [abstract]. In: Proceedings of the AACR Special Conference on the Evolving Landscape of Cancer Modeling; 2020 Mar 2-5; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2020;80(11 Suppl):Abstract nr A13.

Lung adenocarcinoma (LUAD) is a heterogeneous and deadly subtype of non-small cell lung cancer that metastasizes rapidly to distant organs. Recent transcriptional profiling of primary LUADs by TCGA identified three molecular subgroups with unique clinical and biological features. Amongst the most aggressive LUADs are tumors classified in the proximal inflammatory (PI) subtype. However, the molecular mechanisms that dictate metastatic competence of this tumor type remain undefined. Using a bioinformatic approach, we found that PI tumors are significantly enriched for the expression of extracellular matrix genes and their corresponding cell surface receptors compared to tumors of other subtypes. Among these receptors, hyaluronan mediated motility receptor (HMMR) was found to be significantly upregulated. Knockdown of HMMR in LUAD cells decreased their potential to invade, migrate, and form colonies in vitro. In an experimental mouse model of metastasis, suppression of HMMR decreased metastatic incidence and burden. Interestingly, using an orthotopic model of LUAD, suppression of HMMR attenuated tumor initiating capacity of LUAD cells within an inflammatory microenvironment without affecting tumor progression. In distant organs, HMMR is similarly essential for tumor re-initiation and expansion of micrometastases to macrometastases. Our findings suggest that the aggressive behavior of PI LUADs requires the interaction between HMMR and the tumor microenvironment. Citation Format: Laura E. Stevens, Minghui Zhao, Zongzhi Liu, Don Nguyen. A novel molecular subset of metastatic lung adenocarcinoma is defined by the function of the proteoglycan receptor HMMR. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2269. doi:10.1158/1538-7445.AM2015-2269

Background: The receptor tyrosine kinase HER2 is overexpressed in 18-20% of breast cancers and is the target of the highly effective therapy, trastuzumab. Coamplicons are frequent in HER2 amplified tumors, yet their role in response to T is not defined. To identify amplicons which might predict response to T in patients we performed gene expression and copy number analysis in tumor tissue from a preoperative trial with brief exposure to T, followed by T+C. Methods: Fresh tumor core biopsies were taken before at a 2 week timepoint after a single dose of T (8mg/m2) from 80 HER2-overpressing, early breast cancer patients enrolled on a clinical trial of T>T+C. Nucleic acids were extracted using Qiagen AllPrep and were analyzed with Illumina Ref8 and Illumina QUAD 610 SNP arrays. Eight commonly amplified regions (11q13, 14q32, 17q12, 20q13, 21q22, 8p22, 8q24) were identified by FISH probe coordinates and copy number calculated using the GPHMM algorithm. Amplification was defined as 4 or more copies of the amplicon. Gene expression was analyzed in Bioconductor using LIMMA analysis. Genomic biomarkers were compared pathologic complete response (pCR) vs objective response (CR+PR) and non-response (SD+PD) by RECIST criteria at the surgical timepoint. Results: There were 50 tumor pairs with adequate RNA for gene expression and 40 baseline tumors for copy number analysis with 28 paired samples. In the 40 baseline biopsies, the 11q13 amplicon was present in 14/40 (35%) of tumors but never seen in tumors with a pCR (t-test; p=0.004975). Of note, in the tumors with amplification of 11q13 there was no evidence of change in copy number after exposure to T, however numbers were small (7 pairs). Gene expression of the 11q13 region showed no significant change in common amplicon genes after one dose of T. The 17q12 amplicon, which harbors the HER2 locus, was amplified in 35/40 (87.5%) of cases - copy number was not associated with response, however, HER2 and GRB7 gene expression levels significantly declined in pCR tumors compared with Conclusions: Integrated genomic analysis after brief exposure to T may provide useful predictors for response to T+C in early stage, HER2 positive breast cancer. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD07-08.

Lung cancer is the leading cause of cancer-related deaths worldwide. This poor prognosis is due to the rapid metastatic progression of this disease, yet the mechanisms that govern lung cancer dissemination and colonization are unclear. Through an integrated approach, we identified an alveolar cell-selective gene signature that stratifies lung adenocarcinoma (ADC) into molecular subtypes of distinct prognosis and differentiation states. This transcriptional program is regulated in part by the cell fate transcription factors, GATA6 and HOPX, which are normally required for proper alveolar differentiation. In an experimental model, suppression of GATA6 and HOPX cooperatively enhances metastatic competence of lung ADC cells. Whole genome RNA sequencing reveals that this transcriptional network can modulate specific target genes and pathways involved in airway epithelial differentiation and invasion. Our findings identify a novel cell lineage molecular program whose perturbation enhances lung cancer metastasis. Citation Format: William K.C. Cheung, Minghui Zhao, Zongzhi Liu, Paul D. Cao, Laura E. Stevens, Thomas F. Westbrook, Don X. Nguyen. A lineage-selective transcriptional pathway linking lung differentiation and cancer metastasis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3872. doi:10.1158/1538-7445.AM2013-3872

Lung cancer is the leading cause of cancer-related deaths worldwide. This poor prognosis is due to the rapid metastatic progression of this disease, yet the mechanisms that govern lung cancer dissemination and colonization are unclear. Through an integrated approach, we identified an alveolar cell-selective gene signature that stratifies lung adenocarcinoma (ADC) into molecular subtypes of distinct prognosis and differentiation states. This transcriptional program is regulated in part by the cell fate transcription factors, GATA6 and HOPX, which are normally required for proper alveolar differentiation. In an experimental model, suppression of GATA6 and HOPX cooperatively enhances metastatic competence of lung ADC cells. Whole genome RNA sequencing reveals that this transcriptional network can modulate specific target genes and pathways involved in airway epithelial differentiation and invasion. Our findings identify a novel cell lineage molecular program whose perturbation enhances lung cancer metastasis. Citation Format: William K.C. Cheung, Minghui Zhao, Zongzhi Liu, Paul D. Cao, Laura E. Stevens, Thomas F. Westbrook, Don X. Nguyen. A lineage-selective transcriptional pathway linking lung differentiation and cancer metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr B56.

Metastasis and drug resistance are two major challenges in cancer therapies. The occurrence of these two events requires cancer cells to gain new mutations or change their expression profiling, or both, adapt to new environment (i.e. distal organs or drug treatments). These changes likely follow Darwin's evolutionary theory: heterogeneous of cancer cells are generated randomly and more aggressive cells are selected by the tissue environment. Stable inheritance of genome and epigenetic states could delay metastasis and drug resistance. Trimethylated lysine 4 in histone H3 (H3K4me3) is the epigenetic marker for transcriptionally active promoters and the binding site for transcriptional activators. Removing the methyl groups from trimethylated H3K4 on gene promoter regions is a common epigenetic strategy for gene silencing. The JARID1 family members are to date the only known proteins responsible for catalyzing demethylation of trimethylated H3K4. Therefore they are essential in cell differentiation and development. Even though JARID1A (RBP2) was implicated in tumorigenesis of certain cancer types, its exact roles are still poorly understood. I hypothesized that RBP2 contributes to changes of epigenetic states during the occurrence of metastasis and drug resistance. Consistent with my hypothesis, I found that RBP2 is highly expressed in metastatic breast cancer cells and Herceptin tolerant population. Loss of RBP2 decreased lung metastatic gene signature and increase drug sensitivity. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-389. doi:1538-7445.AM2012-LB-389