Giving AXL the axe: targeting AXL in human malignancy.

The receptor tyrosine kinase AXL, activated by a complex interaction between its ligand growth arrest-specific protein 6 and phosphatidylserine, regulates various vital cellular processes, including proliferation, survival, motility, and immunologic response. Although not implicated as an oncogenic driver itself, AXL, a member of the TYRO3, AXL, and MERTK family of receptor tyrosine kinases, is overexpressed in several haematologic and solid malignancies, including acute myeloid leukaemia, non-small cell lung cancer, gastric and colorectal adenocarcinomas, and breast and prostate cancers. In the context of malignancy, evidence suggests that AXL overexpression drives wide-ranging processes, including epithelial to mesenchymal transition, tumour angiogenesis, resistance to chemotherapeutic and targeted agents, and decreased antitumor immune response. As a result, AXL is an attractive candidate not only as a prognostic biomarker in malignancy but also as a target for anticancer therapies. Several AXL inhibitors are currently in preclinical and clinical development. This article reviews the structure, regulation, and function of AXL; the role of AXL in the tumour microenvironment; the development of AXL as a therapeutic target; and areas of ongoing and future investigation.

The RAB5-GEF function of RIN1 regulates multiple steps during Listeria monocytogenes infection.

Listeria monocytogenes is a food-borne pathogenic bacterium that invades intestinal epithelial cells through a phagocytic pathway that relies on the activation of host cell RAB5 GTPases. Listeria monocytogenes must subsequently inhibit RAB5, however, in order to escape lysosome-mediated destruction. Relatively little is known about upstream RAB5 regulators during L. monocytogenes entry and phagosome escape processes in epithelial cells. Here we identify RIN1, a RAS effector and RAB5-directed guanine nucleotide exchange factor (GEF), as a host cell factor in L. monocytogenes infection. RIN1 is rapidly engaged following L. monocytogenes infection and is required for efficient invasion of intestinal epithelial cells. RIN1-mediated RAB5 activation later facilitates the fusion of phagosomes with lysosomes, promoting clearance of bacteria from the host cell. These results suggest that RIN1 is a host cell regulator that performs counterbalancing functions during early and late stages of L. monocytogenes infection, ultimately favoring pathogen clearance.

Selective inhibitor of endosomal trafficking pathways exploited by multiple toxins and viruses.

Pathogenic microorganisms and toxins have evolved a variety of mechanisms to gain access to the host-cell cytosol and thereby exert virulent effects upon the host. One common mechanism of cellular entry requires trafficking to an acidified endosome, which promotes translocation across the host membrane. To identify small-molecule inhibitors that block this process, a library of 30,000 small molecules was screened for inhibitors of anthrax lethal toxin. Here we report that 4-bromobenzaldehyde N-(2,6-dimethylphenyl)semicarbazone, the most active compound identified in the screen, inhibits intoxication by lethal toxin and blocks the entry of multiple other acid-dependent bacterial toxins and viruses into mammalian cells. This compound, which we named EGA, also delays lysosomal targeting and degradation of the EGF receptor, indicating that it targets host-membrane trafficking. In contrast, EGA does not block endosomal recycling of transferrin, retrograde trafficking of ricin, phagolysosomal trafficking, or phagosome permeabilization by Franciscella tularensis. Furthermore, EGA does not neutralize acidic organelles, demonstrating that its mechanism of action is distinct from pH-raising agents such as ammonium chloride and bafilomycin A1. EGA is a powerful tool for the study of membrane trafficking and represents a class of host-targeted compounds for therapeutic development to treat infectious disease.

RIN1 orchestrates the activation of RAB5 GTPases and ABL tyrosine kinases to determine the fate of EGFR.

Stimulation of epidermal growth factor receptor (EGFR) initiates RAS signaling simultaneously with EGFR internalization. Endocytosed EGFR is then either recycled or degraded. EGFR fate is determined in part by the RAS effector RIN1, a guanine nucleotide exchange factor (GEF) for RAB5 GTPases. EGFR degradation was slowed by RIN1 silencing, enhanced by RIN1 overexpression and accelerated by RIN1 localization to the plasma membrane. RIN1 also directly activates ABL tyrosine kinases, which regulate actin remodeling, a function not previously connected to endocytosis. We report that RIN1-RAB5 signaling favors EGFR downregulation over EGFR recycling, whereas RIN1-ABL signaling stabilizes EGFR and inhibits macropinocytosis. RIN1(QM), a mutant that blocks ABL activation, caused EGF-stimulated membrane ruffling, actin remodeling, dextran uptake and EGFR degradation. An ABL kinase inhibitor phenocopied these effects in cells overexpressing RIN1. EGFR activation also promotes RIN1 interaction with BIN1, a membrane bending protein. These findings suggest that RIN1 orchestrates RAB5 activation, ABL kinase activation and BIN1 recruitment to determine EGFR fate.

Immunologic response among HIV-infected patients enrolled in a graduated cost-recovery programme of antiretroviral therapy delivery in Chennai, India.

BACKGROUND & OBJECTIVES: Sustainability of free antiretroviral therapy (ART) roll out programmes in resource-limited settings is challenging given the need for lifelong therapy and lack of effective vaccine. This study was undertaken to compare treatment outcomes among HIV-infected patients enrolled in a graduated cost-recovery programme of ART delivery in Chennai, India. METHODS: Financial status of patients accessing care at a tertiary care centre, YRGCARE, Chennai, was assessed using an economic survey; patients were distributed into tiers 1- 4 requiring them to pay 0, 50, 75 or 100 per cent of their medication costs, respectively. A total of 1754 participants (ART naοve = 244) were enrolled from February 2005-January 2008 with the following distribution: tier 1=371; tier 2=338; tier 3=693; tier 4=352. Linear regression models with generalized estimating equations were used to examine immunological response among patients across the four tiers. RESULTS: Median age was 34; 73 per cent were male, and the majority were on nevirapine-based regimens. Median follow up was 11.1 months. The mean increase in CD4 cell count within the 1 st three months of HAART was 50.3 cells/µl per month in tier 1. Compared to those in tier 1, persons in tiers 2, 3 and 4 had comparable increases (49.7, 57.0, and 50.9 cells/µl per month, respectively). Increases in subsequent periods (3-18 and >18 months) were also comparable across tiers. No differential CD4 gains across tiers were observed when the analysis was restricted to patients initiating ART under the GCR programme. INTERPRETATION & CONCLUSIONS: This ART delivery model was associated with significant CD4 gains with no observable difference by how much patients paid. Importantly, gains were comparable to those in other free rollout programmes. Additional cost-effectiveness analyses and mathematical modelling would be needed to determine whether such a delivery programme is a sustainable alternative to free ART programmes.

Adherence to antiretroviral therapy in patients participating in a graduated cost recovery program at an HIV care center in South India.

In resource-constrained settings, the most frequently cited barrier to optimal antiretroviral therapy (ART) adherence among HIV-infected patients has been the cost of medications. In recent years many subsidized medication programs have been developed to improve ART affordability. A Graduated Cost Recovery program at the largest care center in South India has enrolled 839 eligible patients into four tiers based on an evaluation of their financial information and willingness to pay, of these patients 635 consented to participate in this study. Patients in Tier 1 receive first-line ART at no cost, whereas patients in Tiers 2, 3, and 4 pay 50, 75, and 100%, respectively of the cost of first-line medications based on an assessment of their means. Adherence rates of 95% or greater on 3-day recall were achieved by 84.6% of Tier 1 (n = 156), 71.6% of Tier 2 (n = 141), 72.3% of Tier 3 (n = 242), and 79.2% of Tier 4 (n = 96). These findings suggest patients are highly motivated and that the provision of no-cost ART can promote higher rates of optimal adherence.

Work productivity burden and indirect costs associated with carcinoid syndrome diarrhea.

Objectives: We estimated the indirect costs of work productivity burden from carcinoid syndrome diarrhea (CSD) among employed, insured adults in the United States. Methods: Retrospective cohort study of patients ≥18 years old with CS who did and did not have CSD (2014-2016). Eligible patients had continuous health plan enrollment for ≥12 months prior to their first CS claim and for ≥30 days after. Univariate analyses of clinical and work productivity outcomes and indirect costs were conducted. Multivariate analyses examined associations of CSD with work productivity measures, controlling for baseline characteristics. Results: A total of 1,880 patients with CS were eligible, including 577 with CSD and 1,303 with CS only. Baseline characteristics were generally similar. Patients with CSD missed half of eligible workdays (median 56%, 146/260); those with CS-only missed one-third (38%, 100/260). Work productivity was lower and the associated costs were higher in the presence of CSD. Patients with CSD had more absenteeism, short-term disability, and lost workdays which translated into incremental mean costs of $16,679 greater than those with CS only. Conclusion: Indirect costs related to work productivity losses among adults with CSD are significant, which further add to the burden of CSD to society.

Direct costs of carcinoid syndrome diarrhea among adults in the United States.

BACKGROUND: The burden of carcinoid syndrome (CS) among patients with neuroendocrine tumors is substantial and has been shown to result in increased healthcare resource use and costs. The incremental burden of CS diarrhea (CSD) is less well understood, particularly among working age adults who make up a large proportion of the population of patients with CS. AIM: To estimate the direct medical costs of CSD to a self-insured employer in the United States. METHODS: CS patients with and without CSD were identified in the IBM® MarketScan® Database, including the Medicare Supplemental Coordination of Benefits database. Eligible patients had ≥ 1 medical claim for CS with continuous health plan enrollment for ≥ 12 mo prior to their first CS diagnosis and for ≥ 30 d after, no claims for acromegaly, and no clinical trial participation during the study period (2014-2016). Baseline demographic and clinical characteristics, including comorbidities and treatment, were analyzed using descriptive statistics. Measures of healthcare resource use and costs were compared between patients with and without CSD, including Emergency Department (ED) visits, hospital admissions and length of stay, physician office visits, outpatient services, and prescription claims, using univariate and multivariate analyses to evaluate associations of CSD with healthcare resource use and costs, controlling for baseline characteristics. RESULTS: Overall, 6855 patients with CS were identified of which 4,043 were eligible for the analysis (1352 with CSD, 2691 with CS only). Baseline demographic and clinical characteristics were similar between groups with the exception of age, underlying tumor type, and health insurance plan. Patients with CSD were older, had more comorbidities, and received more somatostatin analog therapy at baseline. Patients with CSD required greater use of healthcare resources and incurred higher costs than their peers without CSD, including hospitalizations (44% vs 25%) and ED visits (55% vs 31%). The total adjusted annual healthcare costs per patient were 50% higher (+ $23865) among those with CSD, driven by outpatient services (+ 56%), prescriptions (+ 48%), ED visits (+ 26%), physician office visits (+ 21%), and hospital admissions (+ 11%). CONCLUSION: The economic burden of CSD is greater than that of CS alone among insured working age adults in the United States, which may benefit from timely diagnosis and management.

Advances in HER2-Targeted Therapy: Novel Agents and Opportunities Beyond Breast and Gastric Cancer.

The introduction of HER2-targeted therapy for breast and gastric patients with ERBB2 (HER2) amplification/overexpression has led to dramatic improvements in oncologic outcomes. In the past 20 years, five HER2-targeted therapies have been FDA approved, with four approved in the past 8 years. HER2-targeted therapy similarly was found to improve outcomes in HER2-positive gastric cancer. Over the past decade, with the introduction of next-generation sequencing into clinical practice, our understanding of HER2 biology has dramatically improved. We have recognized that HER2 amplification is not limited to breast and gastric cancer but is also found in a variety of tumor types such as colon cancer, bladder cancer, and biliary cancer. Furthermore, HER2-targeted therapy has signal of activity in several tumor types. In addition to HER2 amplification and overexpression, there is also increased recognition of activating HER2 mutations and their potential therapeutic relevance. Furthermore, there is a rapidly growing number of new therapeutics targeting HER2 including small-molecule inhibitors, antibody-drug conjugates, and bispecific antibodies. Taken together, an increasing number of patients are likely to benefit from approved and emerging HER2-targeted therapies.

Identification of Actionable Genomic Alterations Using Circulating Cell-Free DNA.

PURPOSE: Cell-free DNA (cfDNA) next-generation sequencing is a noninvasive approach for genomic testing. We report the frequency of identifying alterations and their clinical actionability in patients with advanced/metastatic cancer. PATIENTS AND METHODS: Prospectively consented patients had cfDNA testing performed. Alterations were assessed for therapeutic implications. RESULTS: We enrolled 575 patients with 37 tumor types. Of these patients, 438 (76.2%) had at least one alteration detected, and 205 (35.7%) had one or more alterations of high potential for clinical action. In diseases with 10 or more patients enrolled, 50% or more had at least one alteration deemed of high potential for clinical action. Trials were identified in 80% of patients (286 of 357) with any alteration and in 92% of patients (188 of 205) with one or more alterations of high potential for clinical action of whom 57.6% (118 of 205) had 6 or more months of follow-up available. Of these patients, 10% (12 of 118) had received genomically matched therapy through enrollment in clinical trials (n = 8), off-label drug use (n = 3), or standard of care (n = 1). Although 88.6% of all patients had a performance status of 0 or 1 upon enrollment, the primary reason for not acting on alterations was poor performance status at next treatment change (28.1%; 27 of 96). CONCLUSION: cfDNA testing represents a readily accessible method for genomic testing and allows for detection of genomic alterations in most patients with advanced disease. Utility may be higher in patients interested in investigational therapeutics with adequate performance status. Additional study is needed to determine whether utility is enhanced by testing earlier in the treatment course.

Targeting ERBB2 (HER2) Amplification Identified by Next-Generation Sequencing in Patients With Advanced or Metastatic Solid Tumors Beyond Conventional Indications.

PURPOSE: Human epidermal growth factor receptor 2 (HER2) is an effective therapeutic target in breast and gastric and gastroesophageal junction cancers. However, less is known about the prevalence of ERBB2 (HER2) amplification and the efficacy of HER2-targeted treatment in other tumors. PATIENTS AND METHODS: We assessed HER2 amplification status among 5,002 patients with advanced disease (excluding breast cancer) who underwent next-generation sequencing. We evaluated the clinical benefit of HER2-targeted therapy by measuring the time-dependent overall survival (OS) from the genomic testing results, progression-free survival (PFS), and PFS during HER2-targeted therapy (PFS2) compared with PFS during prior therapy (PFS1). RESULTS: Overall, 122 patients (2.4%) had HER2 amplification, including patients with endometrial (5.3%), bladder (5.2%), biliary or gallbladder (4.9%), salivary (4.7%), and colorectal cancer (3.6%). Forty patients (38%) with nongastric, nongastroesophageal junction, or nonesophageal cancers received at least one line of HER2-targeted therapy. Patients receiving HER2-targeted therapy had a median OS of 18.6 months, compared with 10.9 months for patients who did not receive HER2-targeted therapy (P = .070). On multivariable analysis, HER2-targeted therapy was significantly associated with increased OS (hazard ratio, 0.5; 95% CI, 0.27 to 0.93; P = .029), regardless of sex, age, or number of prior lines of treatment. The PFS2-to-PFS1 ratio was 1.3 or greater in 21 (57%) of 37 patients who received HER2-targeted therapy not in the first line of systemic treatment, and the median PFS2 and PFS1 times were 24 and 13 weeks, respectively (P < .001). CONCLUSION: HER2 amplifications using next-generation sequencing can be identified in a variety of tumor types. HER2-targeted therapy may confer clinical benefit in tumor types other than those for which HER2 inhibitors are approved.

AXL Inhibition Suppresses the DNA Damage Response and Sensitizes Cells to PARP Inhibition in Multiple Cancers.

Epithelial to mesenchymal transition (EMT) is associated with a wide range of changes in cancer cells, including stemness, chemo- and radio-resistance, and metastasis. The mechanistic role of upstream mediators of EMT has not yet been well characterized. Recently, we showed that non-small cell lung cancers (NSCLC) that have undergone EMT overexpress AXL, a receptor tyrosine kinase. AXL is also overexpressed in a subset of triple-negative breast cancers (TNBC) and head and neck squamous cell carcinomas (HNSCC), and its overexpression has been associated with more aggressive tumor behavior and linked to resistance to chemotherapy, radiotherapy, and targeted therapy. Because the DNA repair pathway is also altered in patient tumor specimens overexpressing AXL, it is hypothesized that modulation of AXL in cells that have undergone EMT will sensitize them to agents targeting the DNA repair pathway. Downregulation or inhibition of AXL directly reversed the EMT phenotype, led to decreased expression of DNA repair genes, and diminished efficiency of homologous recombination (HR) and RAD51 foci formation. As a result, AXL inhibition caused a state of HR deficiency in the cells, making them sensitive to inhibition of the DNA repair protein, PARP1. AXL inhibition synergized with PARP inhibition, leading to apoptotic cell death. AXL expression also associated positively with markers of DNA repair across TNBC, HNSCC, and NSCLC patient cohorts. IMPLICATIONS: The novel role for AXL in DNA repair, linking it to EMT, suggests that AXL can be an effective therapeutic target in combination with targeted therapy such as PARP inhibitors in several different malignancies. Mol Cancer Res; 15(1); 45-58. ©2016 AACR.

'The phone reminder is important, but will others get to know about my illness?' Patient perceptions of an mHealth antiretroviral treatment support intervention in the HIVIND trial in South India.

OBJECTIVES: The recent explosion of mHealth applications in the area of HIV care has led to the development of mHealth interventions to support antiretroviral treatment adherence. Several of these interventions have been tested for effectiveness, but few studies have explored patient perspectives of such interventions. Exploring patient perspectives enhances the understanding of how an intervention works or why it does not. We therefore studied perceptions regarding an mHealth adherence intervention within the HIVIND trial in South India. METHODS: The study was conducted at three clinics in South India. The intervention comprised an automated interactive voice response (IVR) call and a pictorial short messaging service (SMS), each delivered weekly. Sixteen purposively selected participants from the intervention arm in the HIVIND trial were interviewed. All participants had completed at least 84 weeks since enrollment in the trial. Perceptions on the usefulness and perceived benefits and risks of receiving the intervention were sought. The interviews were transcribed and analysed using the framework approach to qualitative data analysis. RESULTS: Despite varying perceptions of the intervention, most participants found it useful. The intervention was perceived as a sign of 'care' from the clinic. The IVR call was preferred to the SMS reminder. Two-way communication was preferred to automated calls. Participants also perceived a risk of unintentional disclosure of their HIV status and stigma thereof via the intervention and took initiatives to mitigate this risk. Targeting reminders at those with poor adherence and those in need of social support was suggested. CONCLUSIONS: mHealth adherence interventions go beyond their intended role to provide a sense of care and support to the recipient. Although automated interventions are impersonal, they could be a solution for scale up. Interventions that engage both the recipient and the healthcare provider have greater potential for success. Personalising mHealth interventions could mitigate the risk of stigma and promote their uptake. TRIAL REGISTRATION NUMBER: ISRCTN79261738.

RIN1 regulates cell migration through RAB5 GTPases and ABL tyrosine kinases.

Stimulation of a receptor tyrosine kinase (RTK), such as EGFR, leads to RAS activation followed by RIN1 activation. RIN1, in turn, activates RAB5 family GTPases, as well as ABL tyrosine kinases. As expected, RIN1 expression directly correlates with RAB5-mediated EGFR endocytosis. We previously showed that normal receptor endocytosis and internalized EGFR fate also depend on the ability of RIN1 to concomitantly activate ABL tyrosine kinases, consistent with the established role of ABL kinases in cytoskeleton remodeling and the growing evidence that such remodeling plays a role in endocytic processes. Here we report that growth factor-directed cell migration, a physiological process that involves receptor endocytosis and actin remodeling, also requires the ability of RIN1 to coordinate RAB5 GTPase and ABL tyrosine kinase pathways.