Warfarin Blocks Gas6-Mediated Axl Activation Required for Pancreatic Cancer Epithelial Plasticity and Metastasis

Repurposing "old" drugs can facilitate rapid clinical translation but necessitates novel mechanistic insight. Warfarin, a vitamin K "antagonist" used clinically for the prevention of thrombosis for more than 50 years, has been shown to have anticancer effects. We hypothesized that the molecular mechanism underlying its antitumor activity is unrelated to its effect on coagulation, but is due to inhibition of the Axl receptor tyrosine kinase on tumor cells. Activation of Axl by its ligand Gas6, a vitamin K-dependent protein, is inhibited at doses of warfarin that do not affect coagulation. Here, we show that inhibiting Gas6-dependent Axl activation with low-dose warfarin, or with other tumor-specific Axl-targeting agents, blocks the progression and spread of pancreatic cancer. Warfarin also inhibited Axl-dependent tumor cell migration, invasiveness, and proliferation while increasing apoptosis and sensitivity to chemotherapy. We conclude that Gas6-induced Axl signaling is a critical driver of pancreatic cancer progression and its inhibition with low-dose warfarin or other Axl-targeting agents may improve outcome in patients with Axl-expressing tumors.

Abstract B78: Warfarin blocks Gas6-mediated Axl activation required for pancreatic tumor plasticity and metastasis

Warfarin, a vitamin K antagonist anti-coagulant in clinical use for over 50 years, is reported to exert anti-cancer effects. We hypothesized that the molecular mechanism underlying the observed anti-tumor effects of warfarin is unrelated to generalized anti-coagulation, but rather due to inhibition of the Axl receptor tyrosine kinase. Activation of Axl by its ligand Gas6, a vitamin K-dependent protein, is inhibited at doses of warfarin that do not affect coagulation. Here we document that inhibiting Gas6-mediated Axl activation with low dose warfarin blocks pancreatic cancer progression and spread. Warfarin and other Axl-targeting agents inhibit tumor progression and block spontaneous metastasis in multiple murine models of pancreatic cancer. Warfarin inhibited Axl-dependent tumor cell migration, invasiveness and proliferation while increasing apoptosis and sensitivity to chemotherapy. We demonstrate that Axl signaling is necessary for pancreatic tumor cell epithelial plasticity which is potently reversed by warfarin or selective Axl inhibition in vitro and in vivo. We anticipate Axl is a critical driver of pancreatic cancer progression and its inhibition with low dose warfarin or Axl-selective targeting agents may significantly improve outcome in patients.

Citation Format: Amanda Kirane, Kathleen W. Ludwig, Gry Haaland, Tone Sandal, Renata Ranaweera, Jason E. Toombs, Laura A. Sullivan, Miao Wang, Noah Sorrelle, Sean P. Dineen, Michael T. Dellinger, James B. Lorens, Rolf A. Brekken. Warfarin blocks Gas6-mediated Axl activation required for pancreatic tumor plasticity and metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr B78.

Severe asthma in childhood: assessed in 10 year olds in a birth cohort study

BACKGROUND

Limited information is available regarding the prevalence of severe asthma in children. The present study aimed at investigating the prevalence of severe asthma in an urban child population; secondarily evaluating the applicability of the chosen definition by clinical characteristics.

METHODS

Children enrolled in the prospective birth cohort; the Environment and Childhood Asthma Study in Oslo; were reinvestigated at the age of 10 years (n = 1019). A representative population based cohort of 616 children [mean age 10.9 (SD 0.9) years] with lung function measurements at birth was used for prevalence estimates, whereas all 1019 children (154 with current asthma) attending the 10-year follow-up were included for verification of the definition of severe asthma. Clinical investigations included spirometry, tests of bronchial hyperresponsiveness, skin prick tests and exhaled nitric oxide. Severe asthma was defined as poorly controlled asthma despite treatment with > or = 800 microg budesonide or equivalent; assessed by a detailed structured interview.

RESULTS

The population point prevalence at age 10 years of current severe asthma was 0.5% (three of 616) and among children with current asthma 4.5% (three of 67). The 10/154 children identified as suffering from severe asthma more often had severe bronchial hyperresponsiveness (PD(20) methacholine <1 micromol) (60%vs 22%, P = 0.015), lower median forced expiratory volume in 1 s/forced vital capacity ratio (93%vs 99%, P = 0.04) and higher body mass index (mean BMI 22.3 vs 18.3, P < 0.001) than nonsevere current asthmatics.

CONCLUSIONS

The prevalence of severe asthma was 0.5% in all 10-year olds, and 4.5% among current asthmatics. The severe asthma definition applied in this study is supported by results of clinical investigations.

Effect of inhaled steroids on lung function in young children: a cohort study

The objectives of the present study were to determine the use of inhaled corticosteroids (ICS) for treating recurrent bronchial obstruction (rBO) in young children up to 2 yrs of age and to assess possible modifying effects of ICS on lung function in young children with rBO. From an observational, noninterventional birth cohort of 3,754 newborn children (3,697 with complete questionnaire data by 2 yrs of age), 306 children with documented rBO by age 2 yrs (cases) were identified along with 306 matched controls. Two tidal flow/volume measurements were taken, one at presentation of disease (children were steroid naive) and one at 2 yrs of age (mean age 11.2 and 25.6 months, respectively), from: 21 cases who subsequently received ICS (ICS+); 33 who did not (ICS-); and in 15 controls. The mean +/- SD duration of ICS treatment was 10.3 +/- 6.5 months. The main outcomes were treatment with ICS and baseline ratio of time to peak expiratory flow/total expiratory time (tPTEF/tE). From the entire cohort, 77 children (2.1%) and 21% of children with rBO had received ICS by 2 yrs of age. Baseline tPTEF/tE was significantly lower at the first visit only in ICS+ as compared to ICS- subjects, as well as in ICS+ and ICS- as compared to controls. The mean difference in baseline tPTEF/tE from first to second visit was borderline statistically significant in the ICS+ group only and correlated significantly with duration of ICS treatment. The present observational cohort study demonstrated that one-fifth of young children with recurrent bronchial obstruction had received inhaled corticosteroids. Early inhaled corticosteroid treatment improved lung function by age 2 yrs, mostly in those with the longest duration of treatment.