Targeting Tyro3, Axl, and MerTK Receptor Tyrosine Kinases Significantly Sensitizes Triple-Negative Breast Cancer to CDK4/6 Inhibition.

Triple-negative breast cancer (TNBC) is the most aggressive subtype with high metastasis and mortality rates. Given the lack of actionable targets such as ER and HER2, TNBC still remains an unmet therapeutic challenge. Despite harboring high CDK4/6 expression levels, the efficacy of CDK4/6 inhibition in TNBC has been limited due to the emergence of resistance. The resistance to CDK4/6 inhibition is mainly mediated by RB1 inactivation. Since our aim is to overcome resistance to CDK4/6 inhibition, in this study, we primarily used the cell lines that do not express RB1. Following a screening for activated receptor tyrosine kinases (RTKs) upon CDK4/6 inhibition, we identified the TAM (Tyro3, Axl, and MerTK) RTKs as a crucial therapeutic vulnerability in TNBC. We show that targeting the TAM receptors with a novel inhibitor, sitravatinib, significantly sensitizes TNBC to CDK4/6 inhibitors. Upon prolonged HER2 inhibitor treatment, HER2+ breast cancers suppress HER2 expression, physiologically transforming into TNBC-like cells. We further show that the combined treatment is highly effective against drug-resistant HER2+ breast cancer as well. Following quantitative proteomics and RNA-seq data analysis, we extended our study into the immunophenotyping of TNBC. Given the roles of the TAM receptors in promoting the creation of an immunosuppressive tumor microenvironment (TME), we further demonstrate that the combination of CDK4/6 inhibitor abemaciclib and sitravatinib modifies the immune landscape of TNBC to favor immune checkpoint blockade. Overall, our study offers a novel and highly effective combination therapy against TNBC and potentially treatment-resistant HER2+ breast cancer that can be rapidly moved to the clinic.

Statins affect human glioblastoma and other cancers through TGF-ß inhibition.

The cholesterol-lowering statins have known anti-cancer effects, but the mechanisms and how to utilize statins in oncology have been unclear. We noted in the CellMiner database that statin activity against cancer lines correlated with higher expression of TGF-ß target genes such as SERPINE1 and ZYX. This prompted us to assess whether statins affected TGF-ß activity in glioblastoma (GBM), a cancer strongly influenced by TGF-ß and in dire need of new therapeutic approaches. We noted that statins reduced TGF-ß activity, cell viability and invasiveness, Rho/ROCK activity, phosphorylation and activity of the TGF-ß mediator Smad3, and expression of TGF-ß targets ZYX and SERPINE1 in GBM and GBM-initiating cell (GIC) lines. Statins were most potent against GBM, GIC, and other cancer cells with high TGF-ß activity, and exogenous TGF-ß further sensitized mesenchymal GICs to statins. Statin toxicity was rescued by addition of exogenous mevalonolactone or geranylgeranyl pyrophosphate, indicating that the observed effects reflected inhibition of HMG CoA-reductase by the statins. Simvastatin significantly inhibited the growth of subcutaneous GIC grafts and prolonged survival in GIC intracranially grafted mice. These results indicate where the statins might best be applied as adjunct therapies in oncology, against GBM and other cancers with high TGF-ß activity, and have implications for other statin roles outside of oncology.

Combined c-Met/Trk Inhibition Overcomes Resistance to CDK4/6 Inhibitors in Glioblastoma.

Glioblastoma (GBM) is the most common primary brain malignancy and carries an extremely poor prognosis. Recent molecular studies revealed the CDK4/6-Rb-E2F axis and receptor tyrosine kinase (RTK) signaling to be deregulated in most GBM, creating an opportunity to develop more effective therapies by targeting both pathways. Using a phospho-RTK protein array, we found that both c-Met and TrkA-B pathways were significantly activated upon CDK4/6 inhibition in GBM cells. We therefore investigated the efficacy of combined CDK4/6 and c-Met/TrkA-B inhibition against GBM. We show that both c-Met and TrkA-B pathways transactivate each other, and targeting both pathways simultaneously results in more efficient pathway suppression. Mechanistically, inhibition of CDK4/6 drove NF-κB-mediated upregulation of hepatocyte growth factor, brain-derived neurotrophic factor, and nerve growth factor that in turn activated both c-Met and TrkA-B pathways. Combining the CDK4/6 inhibitor abemaciclib with the c-Met/Trk inhibitor altiratinib or the corresponding siRNAs induced apoptosis, leading to significant synergy against GBM. Collectively, these findings demonstrate that the activation of c-Met/TrkA-B pathways is a novel mechanism involved in therapeutic resistance of GBM to CDK4/6 inhibition and that dual inhibition of c-Met/Trk with CDK4/6 should be considered in future clinical trials.Significance: CDK4/6 inhibition in glioblastoma activates the c-Met and TrkA-B pathways mediated by NF-κB and can be reversed by a dual c-Met/Trk inhibitor. Cancer Res; 78(15); 4360-9. ©2018 AACR.

Targeting the mesenchymal subtype in glioblastoma and other cancers via inhibition of diacylglycerol kinase alpha.

Background: The mesenchymal phenotype in glioblastoma (GBM) and other cancers drives aggressiveness and treatment resistance, leading to therapeutic failure and recurrence of disease. Currently, there is no successful treatment option available against the mesenchymal phenotype. Methods: We classified patient-derived GBM stem cell lines into 3 subtypes: proneural, mesenchymal, and other/classical. Each subtype's response to the inhibition of diacylglycerol kinase alpha (DGKα) was compared both in vitro and in vivo. RhoA activation, liposome binding, immunoblot, and kinase assays were utilized to elucidate the novel link between DGKα and geranylgeranyltransferase I (GGTase I). Results: Here we show that inhibition of DGKα with a small-molecule inhibitor, ritanserin, or RNA interference preferentially targets the mesenchymal subtype of GBM. We show that the mesenchymal phenotype creates the sensitivity to DGKα inhibition; shifting GBM cells from the proneural to the mesenchymal subtype increases ritanserin activity, with similar effects in epithelial-mesenchymal transition models of lung and pancreatic carcinoma. This enhanced sensitivity of mesenchymal cancer cells to ritanserin is through inhibition of GGTase I and downstream mediators previously associated with the mesenchymal cancer phenotype, including RhoA and nuclear factor-kappaB. DGKα inhibition is synergistic with both radiation and imatinib, a drug preferentially affecting proneural GBM. Conclusions: Our findings demonstrate that a DGKα-GGTase I pathway can be targeted to combat the treatment-resistant mesenchymal cancer phenotype. Combining therapies with greater activity against each GBM subtype may represent a viable therapeutic option against GBM.

A randomized trial of the effectiveness of the neutropenic diet versus food safety guidelines on infection rate in pediatric oncology patients.

BACKGROUND: The neutropenic diet (ND) is prescribed to avoid introduction of bacteria into a host's gastrointestinal tract and reduce infection. Due to a lack of evidence to support the ND, there continues to be debate among pediatric oncologists regarding its usefulness. This prospective randomized controlled trial evaluated the difference in neutropenic infection rates in pediatric oncology patients randomized to Food and Drug Administration approved food safety guidelines (FSGs) versus the ND plus FSGs during one cycle of chemotherapy. PROCEDURE: Pediatric patients receiving cancer treatment with myelosuppressive chemotherapy were eligible. Neutropenic infection was the primary outcome and defined as (i) fever with neutropenia or (ii) hospital admission and treatment for clinical infection and neutropenia. The rate of neutropenic infection was compared with Student's t-test for independent samples. Documented infections were identified by comprehensive chart review and compared between groups using a χ2 test. RESULTS: One hundred fifty patients were randomly assigned to FSGs (n = 73) or ND + FSGs (n = 77). The most common diagnoses were acute lymphoblastic leukemia (32%) and sarcoma (32%). There was no significant difference between the groups in the percentage of patients who developed neutropenic infection: FSGs 33% versus ND + FSGs 35% (P = 0.78). Patients randomized to ND + FSGs reported that following the diet required more effort than those on FSGs alone. CONCLUSION: The ND offers no benefit over FSGs in the prevention of infection in pediatric oncology patients undergoing myelosuppressive chemotherapy and adherence requires more effort for patients and families. Institutions caring for children with cancer should consider replacing ND guidelines with FSGs.

CDK4/6 inhibition is more active against the glioblastoma proneural subtype.

Glioblastoma (GBM) is the most common and lethal brain tumor. Gene expression profiling has classified GBM into distinct subtypes, including proneural, mesenchymal, and classical, and identifying therapeutic vulnerabilities of these subtypes is an extremely high priority. We leveraged The Cancer Genome Atlas (TCGA) data, in particular for microRNA expression, to seek druggable core pathways in GBM. The E2F1-regulated miR-17˜92 cluster and its analogs are shown to be highly expressed in proneural GBM and in GSC lines, suggesting the E2F cell cycle pathway might be a key driver in proneural GBM. Consistently, CDK4/6 inhibition with palbociclib preferentially inhibited cell proliferation in vitro in a majority of proneural GSCs versus those of other subtypes. Palbociclib treatment significantly prolonged survival of mice with established intracranial xenografts of a proneural GSC line. We show that most of these sensitive PN GSCs expressed higher levels of CDK6 and had intact Rb1, while two GSC lines with CDK4 overexpression and null Rb1 were highly resistant to palbociclib. Importantly, palbociclib treatment of proneural GSCs upregulated mesenchymal-associated markers and downregulated proneural-associated markers, suggesting that CDK4/6 inhibition induced proneural-mesenchymal transition and underscoring the enhanced role of the E2F cell cycle pathway in the proneural subtype. Lastly, the combination of palbociclib and N,N-diethylaminobenzaldehyde, an inhibitor of the mesenchymal driver ALDH1A3, showed strong synergistic inhibitory effects against proneural GSC proliferation. Taken together, our results reveal that proneural GBM has increased vulnerability to CDK4/6 inhibition, and the proneural subtype undergoes dynamic reprogramming upon palbociclib treatment-suggesting the need for a combination therapeutic strategy.

Combined CDK4/6 and mTOR Inhibition Is Synergistic against Glioblastoma via Multiple Mechanisms.

Purpose: Glioblastoma (GBM) is a deadly brain tumor marked by dysregulated signaling and aberrant cell-cycle control. Molecular analyses have identified that the CDK4/6-Rb-E2F axis is dysregulated in about 80% of GBMs. Single-agent CDK4/6 inhibitors have failed to provide durable responses in GBM, suggesting a need to combine them with other agents. We investigate the efficacy of the combination of CDK4/6 inhibition and mTOR inhibition against GBM.Experimental Design: Preclinical in vitro and in vivo assays using primary GBM cell lines were performed.Results: We show that the CDK4/6 inhibitor palbociclib suppresses the activity of downstream mediators of the mTOR pathway, leading to rebound mTOR activation that can be blocked by the mTOR inhibitor everolimus. We further show that mTOR inhibition with everolimus leads to activation of the Ras mediator Erk that is reversible with palbociclib. The combined treatment strongly disrupts GBM metabolism, resulting in significant apoptosis. Further increasing the utility of the combination for brain cancers, everolimus significantly increases the brain concentration of palbociclib.Conclusions: Our findings demonstrate that the combination of CDK4/6 and mTOR inhibition has therapeutic potential against GBM and suggest it should be evaluated in a clinical trial. Clin Cancer Res; 23(22); 6958-68. ©2017 AACR.

Dedifferentiation of patient-derived glioblastoma multiforme cell lines results in a cancer stem cell-like state with mitogen-independent growth.

Emerging evidence shows that glioblastoma multiforme (GBM) originates from cancer stem cells (CSCs). Characterization of CSC-specific signalling pathways would help identify new therapeutic targets and perhaps lead to the development of more efficient therapies selectively targeting CSCs. Here; we successfully dedifferentiated two patient-derived GBM cell lines into CSC-like cells (induced glioma stem cells, iGSCs) through expression of Oct4, Sox2 and Nanog transcription factors. Transformed cells exhibited significant suppression of epidermal growth factor receptor and its downstream pathways. Compared with parental GBM cells, iGSCs formed large neurospheres even in the absence of exogenous mitogens; they exhibited significant sensitivity to salinomycin and chemoresistance to temozolomide. Further characterization of iGSCs revealed induction of NOTCH1 and Wnt/ß-catenin signalling and expression of CD133, CD44 and ALDH1A1. Our results indicate that iGSCs may help us understand CSC physiology and lead to development of potential therapeutic interventions aimed at differentiating tumour cells to render them more sensitive to chemotherapy or other standard agents.

Diagnostic and therapeutic aspects of Hashimoto's encephalopathy.

OBJECTIVE: To share our experience on clinical presentation and management of patients diagnosed with Hashimoto's Encephalopathy (HE) at Vanderbilt Medical Center between 1999 and 2012. BACKGROUND: HE is a rare disorder characterized by encephalopathy and central nervous system (CNS) dysfunction, elevated antithyroid antibodies, the absence of infection or structural abnormalities in the CNS, and a response to treatment with steroids. The relationship between thyroid antibodies and encephalopathy has remained unresolved. DESIGN/METHODS: Retrospective chart review. RESULTS: We identified 13 patients who met the criteria for the diagnosis of HE. The median age was 49 years (range, 2-66) and all except one were women. Encephalopathy in the form of altered mental status, stroke-like symptoms or seizures, with prompt resolution of symptoms upon receiving steroids, was the commonest presentation, seen in 7 patients. The second commonest presentation was subacute progressive decrease in cognitive function, which reversed within days to weeks after steroid therapy, seen in 4 patients. Electroencephalogram (EEG) was available in 12 patients and was abnormal in 8, showing nonspecific cerebral dysfunction in all 8 and epileptiform activity in 3. Treatment consisted of steroids in the acute phase for 12 of 13 patients with rapid improvement in symptoms. Maintenance therapy was rituximab in 7 patients, intravenous immunoglobulin (IVIg) in 7, azathioprine in 4, mycophenolate mofetil in 3, and methotrexate in 1 (some patients received sequential therapy with different agents). There was complete or near complete resolution of symptoms in 12 of the 13 patients. CONCLUSIONS: We present a cohort of patients in whom CNS dysfunction was associated with elevated antithyroid antibodies and reversal of disease followed immunomodulatory therapies.

Reactive oxygen species and ischemic cerebrovascular disease.

Stroke is an emerging major health problem often resulting in death or disability. Hyperlipidemia, high blood pressure and diabetes are well established risk factors. Endothelial dysfunction associated with these risk factors underlies pathological processes leading to atherogenesis and cerebral ischemic injury. While mechanisms of disease are complex, endothelial dysfunction involves decreased nitric oxide (NO) and elevated levels of reactive oxygen species (ROS). At physiological levels, ROS participate in regulation of cellular metabolism. However, when ROS increase to toxic levels through imbalance of production and neutralization by antioxidant enzymes, they cause cellular injury in the form of lipid peroxidation, protein oxidation and DNA damage. Central nervous system cells are more vulnerable to ROS toxicity due to their inherent higher oxidative metabolism and less antioxidant enzymes, as well as higher content of membranous fatty acids. During ischemic stroke, ROS concentration rises from normal low levels to a peak point during reperfusion possibly underlying apoptosis or cellular necrosis. Clinical trials and animal studies have shown that natural compounds can reduce oxidative stress due to excessive ROS through their antioxidant properties. With further study, we may be able to incorporate these compounds into clinical use with potential efficacy for both the treatment and prevention of stroke.

Analysis of significant decrease in platelet count and thrombocytopenia, graded according to NCI-CTC, as prognostic risk markers for mortality and morbidity.

BACKGROUND: In adult intensive care unit, both thrombocytopenia (TP) and ≥30% decrease in platelet count are associated with increased mortality, morbidity, and length of stay (LOS). The above mentioned observations have not been well reported in pediatric population. National Cancer Institute (NCI) common terminology criteria (CTC) is mainly used to report the adverse effects of cancer therapy, but not for grading TP. METHOD: Retrospective review of medical records was done for 204 patients. TP was graded according to the NCI-CTC. Each grade of TP and significant decrease (≥30%) in platelet count were studied for their association with LOS, mortality, and morbidity such as hospital-acquired pneumonia and positive blood culture. Four study groups were formed according to presence and/or absence of TP and significant decrease in platelet count. These groups were also studied for their association with mortality and LOS. RESULTS: Both ≥30% decrease in platelets and TP (58.3% and 25% of patients, respectively) were associated with higher mortality and longer LOS (P<0.0001). Both have association also with infection. There was a trend of increased mortality with higher TP grade. Grade 4 TP was significantly associated with increased LOS (P=0.0001). When compared with neither group, groups with positive significant decrease were associated with higher mortality and LOS, even in the absence of TP. CONCLUSIONS: We can use the NCI-CTC for classification of TP, which would enable the standardization of TP grading system. A ≥30% decrease in platelet count, even without TP, is a prognostic risk marker for mortality, morbidity, and LOS.

Drop in platelet counts in extremely preterm neonates and its association with clinical outcomes.

BACKGROUND: Thrombocytopenia is a common finding among preterm neonates and has been associated with mortality and morbidities. In recent studies in adults, the drop in platelet numbers has been shown to be a predictor of clinical outcomes. Although drop in the platelet counts with or without thrombocytopenia has also been observed in neonates, its association with mortality and morbidity has not been investigated in the preterm population. OBJECTIVE: To study the prevalence of a ≥ 30% drop in platelet counts in preterm neonates and its association with clinical outcomes. METHODS: Retrospective chart review was done on neonates born at gestational age ≤ 28 weeks and survived for ≥ 7 days. As with the adult studies, a ≥30% drop in platelet numbers were identified at 7 days and 28 days of age and their association with mortality, morbidities, and length of stay (LOS) was investigated. RESULTS: Two hundred eighty-six patients included in the study had a mean gestational age of 26.3 weeks (range, 23 to 28 wk) and birth weight of 899 ± 215 grams. A ≥ 30% drop in platelet counts occurred in 68.1% neonates. It was significantly associated with mortality (P < 0.001), morbidities at both 7 and 28 days [intraventricular bleed (P < 0.01)], retinopathy of prematurity (P<0.01), necrotizing enterocolitis (P < 0.05) and gram-positive infections (P < 0.05), and LOS (P < 0.01). Only those neonates who had a ≥ 30% drop in the platelet numbers developed gram negative and fungal infections. These associations of clinical morbidities and mortality with a ≥ 30% drop in platelet counts were independent of thrombocytopenia. CONCLUSIONS: A ≥ 30% drop in platelet counts is associated with increased mortality, morbidities, and LOS in preterm neonates, independent of thrombocytopenia. As the drop occurs before the onset of clinical morbidity, one potential application is its use to predict the onset of morbidities including necrotizing enterocolitis, intraventricular hemorrhage, and retinopathy of prematurity, and a prolonged LOS and mortality.

NCI classification of thrombocytopenia in extremely preterm neonates and its association with mortality and morbidity.

BACKGROUND: Thrombocytopenia (TP) is a common finding among preterm neonates and has been associated with mortality and morbidities. Yet, there is no consistent classification for neonatal TP. TP in adults has recently been graded by the National Cancer Institute (NCI) Common Toxicity Criteria and has been shown to predict clinical outcomes. OBJECTIVE: To use the NCI classification for TP in preterm neonates and elucidate its association with clinical outcomes. METHODS: Retrospective chart review was done on neonates born at gestational age (GA) ≤28 weeks and survived for ≥7 days. TP was classified as per NCI guidelines at 7 days and 28 days of age and their association with mortality, major morbidities and hospital length of stay (LOS) were investigated. RESULTS: A total of 286 patients were included in the study with a mean GA of 26.3±1.5 weeks and birth weight of 899±215 g. NCI TP grades at 7 days were significantly (P<0.001) associated with mortality, LOS, intraventricular hemorrhage and Gram negative infections. In addition to these outcomes, necrotizing enterocolitis, Gram positive and fungal infections were also significantly associated with NCI TP grades at 28 days. CONCLUSIONS: Classification of TP using the NCI criteria in extreme preterm neonates is clinically applicable. This grading system of platelet counts is significantly associated with mortality, morbidity and LOS in preterm neonates.

Clinical outcomes in extracranial tumor sites and unusual toxicities with concurrent whole brain radiation (WBRT) and Erlotinib treatment in patients with non-small cell lung cancer (NSCLC) with brain metastasis.

BACKGROUND: Thirty percent of newly diagnosed NSCLC patients present with synchronous brain metastases, most of whom are treated with whole brain radiation. Systemic chemotherapy is usually avoided during WBRT due to concerns regarding toxicity. However, concurrent administration of targeted agents, such as Erlotinib, during WBRT may address systemic disease without causing toxicity. We report our institutional data on outcomes and toxicities with this treatment approach. MATERIALS AND METHODS: Medical records of patients with newly diagnosed NSCLC and brain metastases receiving concurrent WBRT and Erlotinib treatment were reviewed. Radiographic response to therapy and toxicities were analyzed. RESULT: Eight patients were identified and 7 were evaluable for response. All patients had intracranial disease control. In the extracranial sites, 3 (37.5%, intent-to-treat) showed partial response (PR), 2 (25%) had stable disease (SD), 1 (12.5%) had progression (PD) and 1 (12.5%) had new air space disease obscuring tumor response assessment. Among the three responders, two were female never smokers, while one was a female current smoker. Unanticipated grade 3 hepatotoxitity, hyponatremia, mental status changes, grade 3 and 4 thrombocytopenia, and grade 4 neutropenia with sepsis were observed. Three deaths occurred without clear signs of disease progression: one from neutropenic sepsis, one from wide spread air space disease, and one from neurologic deterioration. CONCLUSION: Our data demonstrates a high percentage of extracranial tumor response rates with first line Erlotinib in selected NSCLC patients. We observed unexpected serious complications and postulate possible mechanisms. We recommend caution to be exercised when considering Erlotinib treatment during WBRT, particularly in regard to drug-drug interactions and infection control. Data from prospective trials are needed to determine the benefits and toxicities of Erlotinib during WBRT.