PARKIN UBIQUITINATION OF KINDLIN-2 ENABLES MITOCHONDRIA-ASSOCIATED METASTASIS SUPPRESSION

Mitochondria are signaling organelles implicated in cancer, but the mechanisms are elusive. Here, we show that Parkin, an E3 ubiquitin ligase altered in Parkinson's Disease (PD), forms a complex with the regulator of cell motility, Kindlin-2 (K2) at mitochondria of tumor cells. In turn, Parkin ubiquitinates Lys581 and Lys582 using Lys48 linkages, resulting in proteasomal degradation of K2 and shortened half-life from ∼5 h to ∼1.5 h. Loss of K2 inhibits focal adhesion turnover and β1 integrin activation, impairs membrane lamellipodia size and frequency, and inhibits mitochondrial dynamics, altogether suppressing tumor cell-ECM interactions, migration, and invasion. Conversely, Parkin does not affect tumor cell proliferation, cell cycle transitions or apoptosis. Expression of a Parkin ubiquitination-resistant K2 Lys581Ala/Lys582Ala double mutant is sufficient to restore membrane lamellipodia dynamics, correct mitochondrial fusion/fission, and preserve single-cell migration and invasion. In a 3D model of mammary gland developmental morphogenesis, impaired K2 ubiquitination drives multiple oncogenic traits of EMT, increased cell proliferation, reduced apoptosis and disrupted basal-apical polarity. Therefore, deregulated K2 is a potent oncogene and its ubiquitination by Parkin enables mitochondria-associated metastasis suppression.

Intercellular HIF1a reprogams mammary progenitors and myeloid immune evasion to drive high-risk breast lesions

The origin of breast cancer, whether primary or recurrent, is unknown. Here, we show that invasive breast cancer cells exposed to hypoxia release small extracellular vesicles (sEV) that disrupt the differentiation of normal mammary epithelia, expand stem and luminal progenitor cells, and induce atypical ductal hyperplasia and intraepithelial neoplasia. This was accompanied by systemic immunosuppression with increased myeloid cell release of the "alarmin", S100A9, and oncogenic traits of EMT, angiogenesis, and local and disseminated luminal cell invasion, in vivo. In the presence of a mammary gland driver oncogene (MMTV-PyMT), hypoxic sEV accelerated bilateral breast cancer onset and progression. Mechanistically, genetic or pharmacologic targeting of hypoxia-inducible factor-1α (HIF1α) packaged in hypoxic sEV, or homozygous deletion of S100A9 normalized mammary gland differentiation, restored T cell function and prevented atypical hyperplasia. The transcriptome of sEV-induced mammary gland lesions resembled luminal breast cancer, and detection of HIF1α in plasma circulating sEV from luminal breast cancer patients correlated with disease recurrence. Therefore, sEV-HIF1α signaling drives both local and systemic mechanisms of mammary gland transformation at high risk for evolution to multifocal breast cancer. This pathway may provide a readily accessible biomarker of luminal breast cancer progression.

Syntaphilin Regulates Neutrophil Migration in Cancer

Pathologically activated neutrophils (PMN) with immunosuppressive activity, which are termed myeloid-derived suppressor cells (PMN-MDSC), play a critical role in regulating tumor progression. These cells have been implicated in promoting tumor metastases by contributing to premetastatic niche formation. This effect was facilitated by enhanced spontaneous migration of PMN from bone marrow to the premetastatic niches during the early-stage of cancer development. The molecular mechanisms underpinning this phenomenon remained unclear. In this study, we found that syntaphilin (SNPH), a cytoskeletal protein previously known for anchoring mitochondria to the microtubule in neurons and tumor cells, could regulate migration of PMN. Expression of SNPH was decreased in PMN from tumor-bearing mice and patients with cancer as compared with PMN from tumor-free mice and healthy donors, respectively. In Snph-knockout (SNPH-KO) mice, spontaneous migration of PMN was increased and the mice showed increased metastasis. Mechanistically, in SNPH-KO mice, the speed and distance travelled by mitochondria in PMN was increased, rates of oxidative phosphorylation and glycolysis were elevated, and generation of adenosine was increased. Thus, our study reveals a molecular mechanism regulating increased migratory activity of PMN during cancer progression and suggests a novel therapeutic targeting opportunity.

NFκB activation by hypoxic small extracellular vesicles drives oncogenic reprogramming in a breast cancer microenvironment

Small extracellular vesicles (sEV) contribute to the crosstalk between tumor cells and stroma, but the underlying signals are elusive. Here, we show that sEV generated by breast cancer cells in hypoxic (sEV^HYP), but not normoxic (sEV^NORM) conditions activate NFκB in recipient normal mammary epithelial cells. This increases the production and release of inflammatory cytokines, promotes mitochondrial dynamics leading to heightened cell motility and disrupts 3D mammary acini architecture with aberrant cell proliferation, reduced apoptosis and EMT. Mechanistically, Integrin-Linked Kinase packaged in sEV^HYP via HIF1α is sufficient to activate NFκB in the normal mammary epithelium, in vivo. Therefore, sEV^HYP activation of NFκB drives multiple oncogenic steps of inflammation, mitochondrial dynamics, and mammary gland morphogenesis in a breast cancer microenvironment.

Ghost mitochondria drive metastasis through adaptive GCN2/Akt therapeutic vulnerability

Cancer metabolism, including in mitochondria, is a disease hallmark and therapeutic target, but its regulation is poorly understood. Here, we show that many human tumors have heterogeneous and often reduced levels of Mic60, or Mitofilin, an essential scaffold of mitochondrial structure. Despite a catastrophic collapse of mitochondrial integrity, loss of bioenergetics, and oxidative damage, tumors with Mic60 depletion slow down cell proliferation, evade cell death, and activate a nuclear gene expression program of innate immunity and cytokine/chemokine signaling. In turn, this induces epithelial-mesenchymal transition (EMT), activates tumor cell movements through exaggerated mitochondrial dynamics, and promotes metastatic dissemination in vivo. In a small-molecule drug screen, compensatory activation of stress response (GCN2) and survival (Akt) signaling maintains the viability of Mic60-low tumors and provides a selective therapeutic vulnerability. These data demonstrate that acutely damaged, "ghost" mitochondria drive tumor progression and expose an actionable therapeutic target in metastasis-prone cancers.

Protocol for assessing real-time changes in mitochondrial morphology, fission and fusion events in live cells using confocal microscopy

Changes in mitochondrial size, shape, and subcellular position, a process collectively known as mitochondrial dynamics, are exploited for various cancer traits. Modulation of subcellular mitochondrial trafficking and accumulation at the cortical cytoskeleton has been linked to the machinery of cell movements, fueling cell invasion and metastatic spreading. Here, we detail a technique to track changes in mitochondrial volume using a commercial CellLight™ Mitochondria-RFP/GFP reporter and live confocal microscopy. This allows a real-time study of mitochondrial dynamics in live cells.

For complete details on the use and execution of this protocol, please refer to Bertolini et al. (2020).

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Protocol to measure mitochondrial dynamics in live cells

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Use of time-lapse confocal imaging to capture the dynamics of mitochondria

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Deconvolution of 4D images

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Steps for analysis of changes in mitochondrial volume

V-ATPase controls tumor growth and autophagy in a Drosophila model of gliomagenesis

Glioblastoma (GBM), a very aggressive and incurable tumor, often results from constitutive activation of EGFR (epidermal growth factor receptor) and of phosphoinositide 3-kinase (PI3K). To understand the role of autophagy in the pathogenesis of glial tumors in vivo, we used an established Drosophila melanogaster model of glioma based on overexpression in larval glial cells of an active human EGFR and of the PI3K homolog Pi3K92E/Dp110. Interestingly, the resulting hyperplastic glia express high levels of key components of the lysosomal-autophagic compartment, including vacuolar-type H⁺-ATPase (V-ATPase) subunits and ref(2)P (refractory to Sigma P), the Drosophila homolog of SQSTM1/p62. However, cellular clearance of autophagic cargoes appears inhibited upstream of autophagosome formation. Remarkably, downregulation of subunits of V-ATPase, of Pdk1, or of the Tor (Target of rapamycin) complex 1 (TORC1) component raptor prevents overgrowth and normalize ref(2)P levels. In addition, downregulation of the V-ATPase subunit VhaPPA1-1 reduces Akt and Tor-dependent signaling and restores clearance. Consistent with evidence in flies, neurospheres from patients with high V-ATPase subunit expression show inhibition of autophagy. Altogether, our data suggest that autophagy is repressed during glial tumorigenesis and that V-ATPase and MTORC1 components acting at lysosomes could represent therapeutic targets against GBM.

Small Extracellular Vesicle Regulation of Mitochondrial Dynamics Reprograms a Hypoxic Tumor Microenvironment

The crosstalk between tumor cells and the adjacent normal epithelium contributes to cancer progression, but its regulators have remained elusive. Here, we show that breast cancer cells maintained in hypoxia release small extracellular vesicles (sEVs) that activate mitochondrial dynamics, stimulate mitochondrial movements, and promote organelle accumulation at the cortical cytoskeleton in normal mammary epithelial cells. This results in AKT serine/threonine kinase (Akt) activation, membrane focal adhesion turnover, and increased epithelial cell migration. RNA sequencing profiling identified integrin-linked kinase (ILK) as the most upregulated pathway in sEV-treated epithelial cells, and genetic or pharmacologic targeting of ILK reversed mitochondrial reprogramming and suppressed sEV-induced cell movements. In a three-dimensional (3D) model of mammary gland morphogenesis, sEV treatment induced hallmarks of malignant transformation, with deregulated cell death and/or cell proliferation, loss of apical-basal polarity, and appearance of epithelial-to-mesenchymal transition (EMT) markers. Therefore, sEVs released by hypoxic breast cancer cells reprogram mitochondrial dynamics and induce oncogenic changes in a normal mammary epithelium.

Interplay Between V-ATPase G1 and Small EV-miRNAs Modulates ERK1/2 Activation in GBM Stem Cells and Nonneoplastic Milieu

The ATP6V1G1 subunit (V1G1) of the vacuolar proton ATPase (V-ATPase) pump is crucial for glioma stem cells (GSC) maintenance and in vivo tumorigenicity. Moreover, V-ATPase reprograms the tumor microenvironment through acidification and release of extracellular vesicles (EV). Therefore, we investigated the role of V1G1 in GSC small EVs and their effects on primary brain cultures. To this end, small EVs were isolated from patients-derived GSCs grown as neurospheres (NS) with high (V1G1^HIGH-NS) or low (V1G1^LOW-NS) V1G1 expression and analyzed for V-ATPase subunits presence, miRNA contents, and cellular responses in recipient cultures. Our results show that NS-derived small EVs stimulate proliferation and motility of recipient cells, with small EV derived from V1G1^HIGH-NS showing the most pronounced activity. This involved activation of ERK1/2 signaling, in a response reversed by V-ATPase inhibition in NS-producing small EV. The miRNA profile of V1G1^HIGH-NS-derived small EVs differed significantly from that of V1G1^LOW-NS, which included miRNAs predicted to target MAPK/ERK signaling. Mechanistically, forced expression of a MAPK-targeting pool of miRNAs in recipient cells suppressed MAPK/ERK pathway activation and blunted the prooncogenic effects of V1G1^HIGH small EV. These findings propose that the GSC influences the brain milieu through a V1G1-coordinated EVs release of MAPK/ERK-targeting miRNAs. Interfering with V-ATPase activity could prevent ERK-dependent oncogenic reprogramming of the microenvironment, potentially hampering local GBM infiltration. IMPLICATIONS: Our data identify a novel molecular mechanism of gliomagenesis specific of the GBM stem cell niche, which coordinates a V-ATPase-dependent reprogramming of the brain microenvironment through the release of specialized EVs.

The mitophagy effector FUNDC1 controls mitochondrial reprogramming and cellular plasticity in cancer cells

Mitochondria are signaling hubs in eukaryotic cells. Here, we showed that the mitochondrial FUN14 domain-containing protein-1 (FUNDC1), an effector of Parkin-independent mitophagy, also participates in cellular plasticity by sustaining oxidative bioenergetics, buffering ROS production, and supporting cell proliferation. Targeting this pathway in cancer cells suppressed tumor growth but rendered transformed cells more motile and invasive in a manner dependent on ROS-mediated mitochondrial dynamics and mitochondrial repositioning to the cortical cytoskeleton. Global metabolomics and proteomics profiling identified a FUNDC1 interactome at the mitochondrial inner membrane, comprising the AAA+ protease, LonP1, and subunits of oxidative phosphorylation, complex V (ATP synthase). Independently of its previously identified role in mitophagy, FUNDC1 enabled LonP1 proteostasis, which in turn preserved complex V function and decreased ROS generation. Therefore, mitochondrial reprogramming by a FUNDC1-LonP1 axis controls tumor cell plasticity by switching between proliferative and invasive states in cancer.

IDH2 reprograms mitochondrial dynamics in cancer through a HIF-1α-regulated pseudohypoxic state

The role of mitochondria in cancer continues to be debated and paradoxically implicated in opposing functions in tumor growth and tumor suppression. To understand this dichotomy, we explored the function of mitochondrial isocitrate dehydrogenase (IDH)2, a tricarboxylic acid cycle enzyme mutated in subsets of acute leukemias and gliomas, in cancer. Silencing of IDH2 in prostate cancer cells impaired oxidative bioenergetics, elevated reactive oxygen species (ROS) production, and promoted exaggerated mitochondrial dynamics. This was associated with increased subcellular mitochondrial trafficking, turnover of membrane focal adhesion complexes, and enhanced tumor cell migration and invasion, without changes in cell cycle progression. Mechanistically, loss of IDH2 caused ROS-dependent stabilization of hypoxia-inducible factor-1α in normoxia, which was required for increased mitochondrial trafficking and tumor cell movements. Therefore, IDH2 is a dual regulator of cancer bioenergetics and tumor cell motility. This pathway may reprogram mitochondrial dynamics to differentially adjust energy production or promote tumor cell invasion in response to microenvironment conditions.-Wang, Y., Agarwal, E., Bertolini, I., Ghosh, J. C., Seo, J. H., Altieri, D. C. IDH2 reprograms mitochondrial dynamics in cancer through a HIF-1α-regulated pseudohypoxic state.

Abstract 791: V-ATPase in glioma stem cells: V1G1 subunit expression correlates with metabolic behavior and mitochondria activity

Background The vacuolar H+-ATPase (V-ATPase) is a multisubunit proton pump with a role in the acidification of the extra- and intra-cellular environments. Recent evidence connected V-ATPase deregulation and human diseases, including cancer. We previously demonstrated that the overexpression of the catalytic subunit V1G1 is correlated with glioma stem cells (GSC) maintenance. According to V1G1 expression, we sorted glioblastoma patients-derived neurospheres cultures (NS) into two categories: V1G1HIGH and V1G1LOW NS. These NS differ in terms of stem cell genes expression, sphere formation, invasion ability, lysosomal acidity and bioenergetics.

Methods V1G1HIGH, V1G1LOW NS treated with 10nM of BafilomycinA1 (BafA1) or vehicle for 24h (n=3 per group) were used for the functional experiments. Lactate, glucose, ATP levels were measured by commercial kits. Metabolic proteins expression was assessed by western blot. ROS production and mitochondria function were measured by flow cytometry using MitoSox and TMRE assays, respectively.

Results At basal conditions, V1G1LOW NS produce higher levels of lactate (p=0.0379) whereas V1G1HIGH NS show higher levels of extracellular glucose and intracellular ATP. Accordingly, the two NS cultures show an opposite trend in LDH subunits expression with LDHA, which pushes lactate production, being more expressed in V1G1LOW (p=0.0027). Conversely, LDHB that facilities the production of pyruvate from lactate, and the transporter MCT1 are more expressed in V1G1HIGH NS. Interestingly, using the V-ATPase specific inhibitor BafA1, metabolic characteristics of V1G1HIGH are redirected to the V1G1LOW phenotype. Moreover, in V1G1HIGH NS BafA1 induces ROS production and affects mitochondria activity, increasing their depolarization.

Conclusions Taken together these data suggest two distinct metabolic behaviors of NS according to V-ATPase expression. Indeed for energy production V1G1LOW NS could rely on a glycolytic metabolism whereas V1G1HIGH NS on oxidative phosphorylation. Moreover, when overexpressed the proton pump could also have a role in preserving mitochondria polarity. Although preliminary, this is the first evidence reporting a role for V-ATPase in the regulation of cancer stem cell metabolism.

Citation Format: Alessandra M. Storaci, Irene Bertolini, Manuela Caroli, Stefano Ferrero, Valentina Vaira. V-ATPase in glioma stem cells: V1G1 subunit expression correlates with metabolic behavior and mitochondria activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 791.

A GBM-like V-ATPase signature directs cell-cell tumor signaling and reprogramming via large oncosomes

Background

The V-ATPase proton pump controls acidification of intra and extra-cellular milieu in both physiological and pathological conditions. We previously showed that some V-ATPase subunits are enriched in glioma stem cells and in patients with poor survival. In this study, we investigated how expression of a GBM-like V-ATPase pump influences the non-neoplastic brain microenvironment.

Methods

Large oncosome (LO) vesicles were isolated from primary glioblastoma (GBM) neurospheres, or from patient sera, and co-cultured with primary neoplastic or non-neoplastic brain cells. LO transcript and protein contents were analyzed by qPCR, immunoblotting and immunogold staining. Activation of pathways in recipient cells was determined at gene and protein expression levels. V-ATPase activity was impaired by Bafilomycin A1 or gene silencing.

Findings

GBM neurospheres influence their non-neoplastic microenvironment by delivering the V-ATPase subunit V1G1 and the homeobox genes HOXA7, HOXA10, and POU3F2 to recipient cells via LO. LOs reprogram recipient cells to proliferate, grow as spheres and to migrate. Moreover, LOs are particularly abundant in the circulation of GBM patients with short survival time. Finally, impairment of V-ATPase reduces LOs activity.

Interpretation

We identified a novel mechanism adopted by glioma stem cells to promote disease progression via LO-mediated reprogramming of their microenvironment. Our data provide preliminary evidence for future development of LO-based liquid biopsies and suggest a novel potential strategy to contrast glioma progression.

Fund

This work was supported by Fondazione Cariplo (2014-1148 to VV) and by the Italian Minister of Health-Ricerca Corrente program 2017 (to SF).

Abstract 2889: V-ATPase control of EV signaling in glioma stem cells

Background: Recent evidences highlighted that GBM secreted microvesicles (EVs), particularly exosomes (Exo) and large oncosomes (LO), play a major role in the cross-talk between tumor cell and non-neoplastic parenchyma. How GBMs manage to thrive in a highly unfavorable, acidic microenvironment is still unclear, but recent work from our group has identified the vacuolar pump H+-ATPase (V-ATPase) as an important effector of GBM growth and glioma stem cells (GSC) maintenance. Additionally, in ExoCarta database V-ATPase subunits have been described in Exo from different cancer cell types.

Taken together, these data identify V-ATPase as an important driver of gliomagenesis, and a novel, actionable therapeutic target for disease intervention. However, the role of V-ATPase in reprogramming the GBM microenvironment has not been previously investigated.

Methods: Exo and LO were isolated by an Invitrogen kit and serial centrifugation, respectively, from media of patients’ derived GBM neurospheres, enriched in GSC (NS, n=12) or differentiated cultures (n=8). For EVs internalization studies, Exo or LO were stained using FM 1-43 FX dye and the process was followed live for 30’ and at selected time points (30’-4h-24h), using a confocal microscopy or flow cytometry (FACS). Electron microscopy, FACS (of Exo stained with CellTrace and SytoRNA in combination with CD63 coated beads), Nanosight and immunoblotting (for CD63, CD9 and Clathrin) analyses were used to confirm EVs subtypes. Cultures from patients’ derived brain tumor margins or primary GBM (differentiated and not) were used as EVs-recipient cells. miRNA profiling was performed using Taqman Low density arrays and analyzed by R packages. Gene Ontology analysis was performed by DAVID. The study was approved by the Institutional Ethical Committee.

Results: NS are able to produce different EVs, which are internalized by recipient cells after 4 and up to 24 hours of co-culture. Both Exo than LO from NS are able to significantly increase cell growth in recipient cells (brain tumor margins and primary GMB differentiated monolayers), and this effect is stronger with EVs produced by NS with higher V-ATPase expression (V-ATPaseHIGH NS). Primary GBM cells after co-culture with EVs are able to produce a higher number of NS and V-ATPase activity block by BafilomycinA1 in NS-producing EVs completely revert this effect. Finally, the co-culture of V-ATPaseLOW NS with EVs from V-ATPaseHIGH NS increases their motility in collagen matrixes.

At molecular level, profiling of Exo-derived miRNAs distinguishes differentiated cultures from NS and, among NS, V-ATPaseHIGH cultures. In silico analysis and annotation of miRNA target genes from V-ATPaseHIGH–derived Exo showed an enrichment of cancer, cell cycle and PI3K/Akt pathways.

Conclusions: Altogether, these data point toward the central role of different EV types in GBM communication and suggest a role of the V-ATPase proton pump in regulating EV’s contents.

Citation Format: Irene Bertolini, Andrea Terrasi, Andrea Di Cristofori, Silvano Bosari, Valentina Vaira. V-ATPase control of EV signaling in glioma stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2889. doi:10.1158/1538-7445.AM2017-2889

Mitochondrial Akt Regulation of Hypoxic Tumor Reprogramming

Hypoxia is a universal driver of aggressive tumor behavior, but the underlying mechanisms are not completely understood. Using a phosphoproteomics screen, we now show that active Akt accumulates in the mitochondria during hypoxia and phosphorylates pyruvate dehydrogenase kinase 1 (PDK1) on Thr346 to inactivate the pyruvate dehydrogenase complex. In turn, this pathway switches tumor metabolism toward glycolysis, antagonizes apoptosis and autophagy, dampens oxidative stress, and maintains tumor cell proliferation in the face of severe hypoxia. Mitochondrial Akt-PDK1 signaling correlates with unfavorable prognostic markers and shorter survival in glioma patients and may provide an "actionable" therapeutic target in cancer.

The vacuolar H+ ATPase is a novel therapeutic target for glioblastoma

The vacuolar H⁺ ATPase (V-ATPase) is a proton pump responsible for acidification of cellular microenvironments, an activity exploited by tumors to survive, proliferate and resist to therapy. Despite few observations, the role of V-ATPase in human tumorigenesis remains unclear.

We investigated the expression of ATP6V0C, ATP6V0A2, encoding two subunits belonging to the V-ATPase V0 sector and ATP6V1C, ATP6V1G1, ATPT6V1G2, ATP6V1G3, which are part of the V1 sector, in series of adult gliomas and in cancer stem cell-enriched neurospheres isolated from glioblastoma (GBM) patients. ATP6V1G1 expression resulted significantly upregulated in tissues of patients with GBM and correlated with shorter patients' overall survival independent of clinical variables.

ATP6V1G1 knockdown in GBM neurospheres hampered sphere-forming ability, induced cell death, and decreased matrix invasion, a phenotype not observed in GBM monolayer cultures. Treating GBM organotypic cultures or neurospheres with the selective V-ATPase inhibitor bafilomycin A1 reproduced the effects of ATP6V1G1 siRNA and strongly suppressed expression of the stem cell markers Nestin, CD133 and transcription factors SALL2 and POU3F2 in neurospheres.

These data point to ATP6V1G1 as a novel marker of poor prognosis in GBM patients and identify V-ATPase inhibition as an innovative therapeutic strategy for GBM.

Abstract P1-08-31: Putative role of genetic variants of eNOS in survival and toxicity of patients given antiangiogenic therapy

Background: The development of tumor angiogensis is mainly driven by vascular endothelial growth factor (VEGF), which is strongly overexpressed in many cancers. VEGF induces the expression of the endothelial nitric oxide (NO) synthase (eNOS) and the resultant overproduction of NO may be associated with recruitment of inflammatory cells, disruption of endothelial barrier, edema and impaired drug delivery within tumors (1). Functional polymorphisms in the eNOS gene, including -786C>T and 894G>T, have been associated with impaired production of NO and higher incidence of hypertension (HT) (2), diabetic nephropathy (3) and glaucoma (4). Since suppression of VEGF-eNOS signal transduction by antiangiogenic drugs may normalize tumor vasculature by restoring interstitial fluid pressure and drug distribution in tumors, but may induce HT in patients, the purpose of this study was to examine the association between the major eNOS variants -786C>T and 894G>T with treatment outcome and risk of HT in metastatic breast cancer (MBC) patients given bevacizumab. Methods: Sixty-five MBC patients given bevacizumab as per approved indication were enrolled. Main characteristics were: mean age 49.5 years (range 29-73) at first diagnosis, 53 years (range 34-74) at metastatic progression and PS 0-1. Four subjects with HT and 1 patient with compensated cardiovascular disease were also included. First-line chemotherapy for metastatic disease was taxol plus bevacizumab. Germline DNA was extracted from peripheral blood with the Qiamp Mini Kit (Qiagen, Milano, Italy) and examined for eNOS -786C>T and 894G>T variants by Real Time PCR (Life Sciences 7900HT platform) and automatic sequencing (Life Sciences 3100 Avant). The study was approved by the local Ethics Committee. Results: Genotype frequencies are reported below (Table 1). The presence of -786TT genotype was associated with longer PFS compared with the other genotypes (median PFS 95%CI, CC/CT = 9 vs TT = 12 months, Log-rank [Mantel Cox] test p = 0.0066), but not with any grade of HT. Also the 894GT/TT was associated with longer PFS compaed with the GG homozygous wild-type genotype (median PFS 95%CI, GG = 7,5 vs GT/TT = 10 months, Log-rank [Mantel-Cox] test p = 0,0497). The incidence and severity of HT did not vary among genotypes. Conclusion: Patients bearing deficient eNOS variant did not experience higher risk or severity of HT with respect to the wild-type allele but enjoied a longer PFS.

Table 1. Genotype frequenciesSNPFrequencies%Frequencies%Frequencies%-786C>TCCCTTT 37%33.8%26.2%894G>TGGGTTT 41.5%53.8%4.6%

References

1. Goel S et al. Physiol Rev 2011;91:1071

2. Niu W, Qi Y. PLoS One 2011;6:e24266

3. Rahimi Z et al. Dis Markers 2013;34:437

4. Awadalla MS et al. Invest Ophtalmol Vis Sci 2013;54:2108.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-08-31.

Abstract P5-17-06: The deficient eNOS c.894G>T genotype is not associated with increased severity of hypertension and proteinuria in breast cancer patients receiving bevacizumab

Background. Tumor angiogenesis is a complex process involving a wide array of effector molecules and stromal cells. In tumor tissue, vasculature is structurally and functionally abnormal, causing elevated interstitial pressure and irregular perfusion. The expression of vascular endothelial growth factor (VEGF), the most important angiogenic factor, is enhanced in many tumors. VEGF may induce nitric oxide (NO) production via up-regulation of the endothelial NO synthase (eNOS, NOS3) and the resultant overproduction of NO is associated with vasodilation and edema within tumors (Goel S et al. Physiol Rev 2011;91:1071). eNOS plays an important physiologic role in maintaining blood pressure homeostasis and vascular integrity by providing constitutive release of NO in endothelial cells. Functional variants of the eNOS gene, including the single-nucleotide polymorphism rs1799983 (c.894G>T, p. Asp298Glu) at codon 298, have been associated with reduced function of eNOS and higher incidence of hypertension (HT) (Niu W, Qi Y. PLoS One 2011;6:e24266).

Purpose. Since suppression of VEGF-eNOS axis by anti-angiogenic therapies is considered a causative factor of HT in patients, the purpose of this study was to examine whether the major eNOS non-synonymous variant c.894G>T may be associated with increased risk of developing hypertension (HT) and proteinuria (PU) in breast cancer patients treated with bevacizumab.

Patients and methods. Forty-one metastatic breast cancer patients given bevacizumab as per standard of care were enrolled. Main characteristics were: median age 49.5 years (range 29–73) at first diagnosis, 53 years (range 34–74) at metastatic disease; PS 0–1 in all patients; 4 subjects with hypertension and 1 patient with compensated cardiovascular disease at diagnosis. Twenty-six subjects had received neoadjuvant or adjuvant chemotherapy based on anthracycline and taxane; first-line chemotherapy for metastatic disease was paclitaxel plus bevacizumab for all patients; 14 subjects received hormone-therapy for metastatic disease (range 1–5 lines). Germline DNA was extracted from peripheral blood and used to screen patients for eNOS c.894G>T variant by automatic sequencing. The study was approved by the local Ethics Committee.

Results. Three patients (7.3%) were homozygous variant c.894TT, 12 (29.3%) homozygous wild-type c.894GG and the remaining 26 (63.4%) were heterozygous c.894GT. The c.894TT patients had no HT or PU at baseline and developed grade (G) 1, 2, 2 HT, respectively, and in one case PU during treatment. G1, 2 and 3 HT developed in 4, 5 and 2 c.894GG subjects, respectively, while PU was observed in 7/12 (58%) patients. The full range of HT grades and PU were observed in heterozygous subjects. Thirty-seven patients achieved one of the following: partial remission, minimal response or stable disease upon treatment with bevacizumab in combination with chemotherapy; 3 subjects had progressive disease and 1 was not evaluable.

Conclusions. The presence of the mutant T allele of c.894G>T is not associated with increased severity of HT and PU; therefore, bevacizumab can be administered at no increased risk in TT patients with respect to the wild-type GG population.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-17-06.