Project description:In order to identify the contribution of Lkb1 loss to Pten driven prostate cancer progression, we engineered a prostate conditional mutant mice in which was induced the loss of Lkb1 in combination with heterozygous loss of the prostate tumor suppressor Pten (Ptenpc+/- Lkb1pc-/-). This mouse model developed metastatic prostate squamous cell carcinoma. We compared this tumor type with the adenocarcinomas developed in Ptenpc-/- Lkb1pc+/+ mice. We carried out microdissection and RNA extraction of tumor tissues embedded in paraffin of Ptenpc+/- Lkb1pc-/- and Ptenpc-/- Lkb1pc+/+. To distinguish between early and late phenotype of prostate squamous cell carcinoma, we compared Ptenpc+/- Lkb1pc-/- tumor tissues collected at the age of six and ten months of age among them and with Ptenpc-/- Lkb1pc+/+ mouse prostate tissue.
Project description:Germline mutations in LKB1 (STK11) are associated with the Peutz–Jeghers syndrome (PJS), which includes aberrant mucocutaneous pigmentation, and somatic LKB1 mutations occur in 10% of cutaneous melanoma. By somatically inactivating Lkb1 with K-Ras activation (+/- p53 loss) in murine melanocytes, we observed variably pigmented and highly metastatic melanoma with 100% penetrance. LKB1 deficiency resulted in increased phosphorylation of the SRC-family kinase (SFK) YES and the subsequent expansion of a CD24+ cell population which showed increased metastatic behavior in vitro and in vivo relative to isogenic CD24- cells. These results suggest that LKB1 inactivation in the context of RAS activation facilitates metastasis by inducing a SFK-dependent expansion of a pro-metastatic, CD24+ tumor sub-population reference x sample
Project description:Germline mutations in LKB1 (STK11) are associated with the Peutz–Jeghers syndrome (PJS), which includes aberrant mucocutaneous pigmentation, and somatic LKB1 mutations occur in 10% of cutaneous melanoma. By somatically inactivating Lkb1 with K-Ras activation (+/- p53 loss) in murine melanocytes, we observed variably pigmented and highly metastatic melanoma with 100% penetrance. LKB1 deficiency resulted in increased phosphorylation of the SRC-family kinase (SFK) YES and the subsequent expansion of a CD24+ cell population which showed increased metastatic behavior in vitro and in vivo relative to isogenic CD24- cells. These results suggest that LKB1 inactivation in the context of RAS activation facilitates metastasis by inducing a SFK-dependent expansion of a pro-metastatic, CD24+ tumor sub-population
Project description:Metastasis is the leading cause of cancer-related deaths, enabling cancer cells to expand to secondary tumor sites and compromise systemic organ function1. Given that primary tumors and metastases often share the same constellation of functional driver mutations2–4, the mechanisms driving their distinct phenotypes are unclear. Here, we show that inactivation of a frequently mutated tumor suppressor gene, liver kinase B1 (LKB1), has evolving effects throughout lung cancer progression, differentially re-programming the epigenetic landscape of early-stage primary tumors compared to late-stage metastases. By integrating genome-scale CRISPR/Cas9 screening with bulk and single-cell multi-omic analyses, we unexpectedly identify LKB1 as a master regulator of chromatin state in lung adenocarcinoma primary tumors. Using an in vivo model of metastatic progression, we further reveal that loss of LKB1 activates the early endoderm transcription factor SOX17 in metastases and metastatic-like sub-populations of cancer cells within primary tumors. SOX17 expression is both necessary and sufficient to drive a second wave of epigenetic changes in LKB1-deficient cells that enhances metastatic ability. Overall, our study demonstrates how the downstream effects of an individual driver mutation can change throughout cancer development, with implications for stage-specific therapeutic resistance mechanisms and the gene regulatory underpinnings of metastatic evolution.
Project description:Metastatic uveal melanomas are highly resistant to all existing treatments. To address this critical issue, we performed a genome-wide CRISPR-Cas9 knockout screen, which revealed the LKB1-SIK2 module in restraining uveal melanoma tumorigenesis. Functionally, LKB1 loss enhances proliferation and survival through SIK2 inhibition and up-regulation of the sodium/calcium (Na+/Ca2+) exchanger SLC8A1. This signalling cascade promotes increased level of intracellular calcium and mitochondrial reactive oxygen species, two hallmarks of cancer. We further demonstrate that combination of an SLC8A1 inhibitor and a mitochondria-targeted antioxidant promotes enhanced cell death efficacy in LKB1- and SIK2-negative uveal melanoma cells compared to control cells. We also designed an LKB1-deficient prognostic gene signature of patient survival that may be predictive of response to this combination. Our data thus identify not only metabolic vulnerabilities, but also new prognostic markers, thereby providing a therapeutic strategy for particular subtypes of metastatic uveal melanoma.
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:We characterize the phenotype of mice in which the deletion of Lkb1 has been targeted in the liver. Lack of Lkb1 in the liver results in bile duct paucity leading to cholestasis. This phenotype is similar to that obtained upon inactivation of Notch signaling in the liver. We test the hypothesis of a functional overlap between the Lkb1 and Notch pathways by gene expression profiling of livers deficent in Lkb1 or in the Notch mediator RbpJκ. We used AlfpCre mice for liver-specific deletion of LKB1 that were crossed with a conditional knockout mouse model (LKB1 floxed mice). We used also AlfpCre mice for liver-specific inactivation of the Notch pathway. AlfpCre mice were crossed with the RbpJκ floxed mice. RNA was extracted from the liver of LKB1 KO mice (Lkb1Floxed, AlfpCre positive mice) and their wild-type counterpart (Lkb1Floxed, AlfpCre negative mice). RNA was also extracted from liver of RbpJK KO mice (RbpJK floxed, AlfpCre positive) and their wild type mice (RbpJK floxed, AlfpCe negative). 6 samples for the liver-specific deletion of LKB1 corresponding to 3 KO LKB1 (Cre positive) and 3 normal liver (Cre negative). 6 samples for the liver-specific inactivation of the Notch pathway corresponding to 3 KO RbpJk (Cre positive) and 3 normal liver (Cre negative).
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.
Project description:Gene dosage is a key defining factor to understand cancer pathogenesis and progression, which requires the development of experimental models that aid better deconstruction of the disease. Here, we model an aggressive form of prostate cancer and show the unconventional association of LKB1 dosage to prostate tumorigenesis. Whereas loss of Lkb1 alone in the murine prostate epithelium was inconsequential for tumorigenesis, its combination with an oncogenic insult, illustrated by Pten heterozygosity, elicited lethal metastatic prostate cancer. Despite the low frequency of LKB1 deletion in patients, this event was significantly enriched in lung metastasis. Modeling the role of LKB1 in cellular systems revealed that the residual activity retained in a reported kinase-dead form, LKB1K78I, was sufficient to hamper tumor aggressiveness and metastatic dissemination. Our data suggest that prostate cells can function normally with low activity of LKB1, whereas its complete absence influences prostate cancer pathogenesis and dissemination.