Integrated molecular profiling of patient-derived ovarian cancer models identifies clinically relevant signatures and tumor vulnerabilities.

High-grade serous ovarian carcinoma (HGSOC) is a highly aggressive and intractable neoplasm, mainly because of its rapid dissemination into the abdominal cavity, a process that is favored by tumor-associated peritoneal ascites. The precise molecular alterations involved in HGSOC onset and progression remain largely unknown due to the high biological and genetic heterogeneity of this tumor. We established a set of different tumor samples (termed the As11-set) derived from a single HGSOC patient, consisting of peritoneal ascites, primary tumor cells, ovarian cancer stem cells (OCSC) and serially propagated tumor xenografts. The As11-set was subjected to an integrated RNA-seq and DNA-seq analysis which unveiled molecular alterations that marked the different types of samples. Our profiling strategy yielded a panel of signatures relevant in HGSOC and in OCSC biology. When such signatures were used to interrogate the TCGA dataset from HGSOC patients, they exhibited prognostic and predictive power. The molecular alterations also identified potential vulnerabilities associated with OCSC, which were then tested functionally in stemness-related assays. As a proof of concept, we defined PI3K signaling as a novel druggable target in OCSC.

Antimetastatic and antiangiogenic activity of trabectedin in cutaneous melanoma.

Trabectedin is a marine-derived antineoplastic drug. Besides targeting the cancer cells, trabectedin has a peculiar activity on the tumor microenvironment with marked effects on the vasculature and the immune response. Because a favorable microenvironment is a key factor in the progression of cutaneous melanoma, we hypothesized that trabectedin might affect the growth and metastasis of this highly aggressive cancer. This study shows that trabectedin inhibited the subcutaneous growth of the murine melanoma B16-BL6 and K1735-M2. In line with its known activities on the environment of other tumor types, it caused a significant reduction of tumor blood vessel density and tumor-associated macrophages. Trabectedin had a significant antimetastatic activity, inhibiting the formation of lung colonies following intravenous injection of B16-BL6 or K1735-M2 cells. The drug was also active in a clinically relevant spontaneous metastasis assay, where it inhibited lung metastasis when administered before (neoadjuvant) or after (adjuvant) surgical removal of the primary tumor. Relevant to its antimetastatic activity, trabectedin inhibited melanoma cell invasiveness in vitro, associated with increased tissue inhibitor of metalloproteinase-1 production and alteration in cell shape and cytoskeleton organization. This study shows that trabectedin affects melanoma growth and metastasis, acting with tumor-dependent mechanisms on both the tumor cells and the vascular and the inflammatory tumor microenvironment.

Tumor progression and metastatic dissemination in ovarian cancer after dose-dense or conventional paclitaxel and cisplatin plus bevacizumab.

The efficacy of therapeutic regimens incorporating weekly or every-3-weeks paclitaxel (PTX) for ovarian cancer is debated. We investigated the addition of bevacizumab in regimens of chemotherapy with different PTX doses and schedules in preclinical models. Treatments were cisplatin (DDP) with weekly PTX (conventional), or dose-dense-equi (every other day to the conventional cumulative dose), or dose-dense-high (total dose 1.5 times higher), with or without bevacizumab. Treatment efficacy was evaluated analyzing tumor growth in different time-windows in two patient-derived ovarian cancer xenografts with different sensitivity to cisplatin. Tumor progression, metastasis and survival were studied in ovarian cancer models growing orthotopically and disseminating in the mouse peritoneal cavity. Short-term effects on cell cycle, tumor cell proliferation/apoptosis and vasculature were evaluated by flow cytometry and immunohistochemistry. PTX dose-dense (with/without DDP) was superior to the conventional scheme in a dose-dependent manner; the high efficacy was confirmed by the lower ratio of tumor to normal cells. All schemes benefited from bevacizumab, which reduced tumor vessels. However, DDP/PTX dose-dense-high (only chemotherapy) was at least as active as DDP/PTX conventional plus bevacizumab. DDP/PTX dose-dense-high plus bevacizumab was the most effective in delaying tumor progression, though it did not prolong mouse survival and the continuous treatment with bevacizumab was associated with a malignant disease. These findings indicate that the effect of bevacizumab in combination with chemotherapy may depend on the schedule-dose of the treatment and help to explain the unclear benefits after bevacizumab.

Drug-Homogeneity Index in Mass-Spectrometry Imaging.

Enhancing drug penetration in solid tumors is an interesting clinical issue of considerable importance. In preclinical research, mass-spectrometry imaging is a promising technique for visualizing drug distribution in tumors under different treatment conditions and its application in this field is rapidly increasing. However, in view of the huge variability among MSI data sets, drug homogeneity is usually manually assessed by an expert, and this approach is biased by interobserver variability and lacks reproducibility. We propose a new texture-based feature, the drug-homogeneity index (DHI), which provides an objective, automated measure of drug homogeneity in MSI data. A simulation study on synthetic data sets showed that previously known texture features do not give an accurate picture of intratumor drug-distribution patterns and are easily influenced by the tumor-tissue morphology. The DHI has been used to study the distribution profile of the anticancer drug paclitaxel in various xenograft models, which were either pretreated or not pretreated with antiangiogenesis compounds. The conclusion is that drug homogeneity is better in the pretreated condition, which is in agreement with previous experimental findings published by our group. This study shows that DHI could be useful in preclinical studies as a new parameter for the evaluation of protocols for better drug penetration.

Contribution of tumor endothelial cells to drug resistance: anti-angiogenic tyrosine kinase inhibitors act as p-glycoprotein antagonists.

Tumor endothelial cells (TEC) differ from the normal counterpart, in both gene expression and functionality. TEC may acquire drug resistance, a characteristic that is maintained in vitro. There is evidence that TEC are more resistant to chemotherapeutic drugs, substrates of ATP-binding cassette (ABC) transporters. TEC express p-glycoprotein (encoded by ABCB1), while no difference in other ABC transporters was revealed compared to normal endothelia. A class of tyrosine kinase inhibitors (TKI), used as angiostatic compounds, interferes with the ATPase activity of p-glycoprotein, thus impairing its functionality. The exposure of ovarian adenocarcinoma TEC to the TKIs sunitinib or sorafenib was found to abrogate resistance (proliferation and motility) to doxorubicin and paclitaxel in vitro, increasing intracellular drug accumulation. A similar effect has been reported by the p-glycoprotein inhibitor verapamil. No beneficial effect was observed in combination with cytotoxic drugs that are not p-glycoprotein substrates. The current paper reviews the mechanisms of TEC chemoresistance and shows the role of p-glycoprotein in mediating such resistance. Inhibition of p-glycoprotein by anti-angiogenic TKI might contribute to the beneficial effect of these small molecules, when combined with chemotherapy, in counteracting acquired drug resistance.

Antiangiogenic activity of trabectedin in myxoid liposarcoma: involvement of host TIMP-1 and TIMP-2 and tumor thrombospondin-1.

Trabectedin is a marine natural product, approved in Europe for the treatment of soft tissue sarcoma and relapsed ovarian cancer. Clinical and experimental evidence indicates that trabectedin is particularly effective against myxoid liposarcomas where response is associated to regression of capillary networks. Here, we investigated the mechanism of the antiangiogenic activity of trabectedin in myxoid liposarcomas. Trabectedin directly targeted endothelial cells, impairing functions relying on extracellular matrix remodeling (invasion and branching morphogenesis) through the upregulation of the inhibitors of matrix metalloproteinases TIMP-1 and TIMP-2. Increased TIMPs synthesis by the tumor microenvironment following trabectedin treatment was confirmed in xenograft models of myxoid liposarcoma. In addition, trabectedin upregulated tumor cell expression of the endogenous inhibitor thrombospondin-1 (TSP-1, a key regulator of angiogenesis-dependent dormancy in sarcoma), in in vivo models of myxoid liposarcomas, in vitro cell lines and primary cell cultures from patients' myxoid liposarcomas. Chromatin Immunoprecipitation analysis showed that trabectedin displaced the master regulator of adipogenesis C/EBPß from the TSP-1 promoter, indicating an association between the up-regulation of TSP-1 and induction of adipocytic differentiation program by trabectedin. We conclude that trabectedin inhibits angiogenesis through multiple mechanisms, including directly affecting endothelial cells in the tumor microenvironment--with a potentially widespread activity--and targeting tumor cells' angiogenic activity, linked to a tumor-specific molecular alteration.

Vascular endothelial growth factor c promotes ovarian carcinoma progression through paracrine and autocrine mechanisms.

Vascular endothelial growth factor C (VEGFC) has been reported to promote tumor progression in several tumor types, mainly through the stimulation of lymphangiogenesis and lymphatic metastasis. However, the expression and biological significance of the VEGFC/VEGF receptor (VEGFR)-3 pathway in ovarian cancer growth and dissemination are unclear, and have been investigated in this study. Soluble VEGFC was detected in the plasma and ascites of patients with ovarian carcinoma, and VEGFR3 expression was found in their tumor tissues. In human ovarian carcinoma xenograft models, high levels of soluble VEGFC in ascites and serum were detected, in association with disease progression, tumor burden, and volume of ascites. Peak VEGFC expression preceded para-aortic lymph node infiltration by HOC8 neoplastic cells. Histological detection of tumor cells in blood and lymphatic vessels indicated both hematogenous and lymphatic dissemination. Overexpression of VEGFC in the VEGFR3-positive and luciferase-expressing IGROV1 cells promoted carcinoma dissemination after orthotopic transplantation in the ovary of immunodeficient mice. In vitro, VEGFC released by the tumor cells stimulated tumor cell migration in an autocrine manner. Cediranib, an inhibitor of VEGFR1-3 and c-kit, inhibited in vivo metastasis of VEGFC-overexpressing IGROV1 and in vitro autocrine effects. These findings suggest that the VEGFC/VEGFR3 pathway acts as an enhancer of ovarian cancer progression through autocrine and paracrine mechanisms, hence offering a potential target for therapy.

BRCA1 foci test as a predictive biomarker of olaparib response in ovarian cancer patient-derived xenograft models.

Standard therapy for high-grade ovarian carcinoma includes surgery followed by platinum-based chemotherapy and poly-ADP ribose polymerase inhibitors (PARPis). Deficiency in homologous recombination repair (HRD) characterizes almost half of high-grade ovarian carcinomas and is due to genetic and epigenetic alterations in genes involved in HR repair, mainly BRCA1/BRCA2, and predicts response to PARPi. The academic and commercial tests set up to define the HRD status of the tumor rely on DNA sequencing analysis, while functional tests such as the RAD51 foci assay are currently under study, but have not been validated yet and are available for patients. In a well-characterized ovarian carcinoma patient-derived xenograft platform whose response to cisplatin and olaparib, a PARPi, is known, we assessed the association between the BRCA1 foci score, determined in formalin-fixed paraffin-embedded tumor slices with an immunofluorescence technique, and other HRD biomarkers and explored the potential of the BRCA1 foci test to predict tumors' response to cisplatin and olaparib. The BRCA1 foci score was associated with both tumors' HRD status and RAD51 foci score. A low BRCA1 foci score predicted response to olaparib and cisplatin, while a high score was associated with resistance to therapy. As we recently published that a low RAD51 foci score predicted olaparib sensitivity in our xenobank, we combined the two scores and showed that the predictive value was better than with the single tests. This study reports for the first time the capacity of the BRCA1 foci test to identify HRD ovarian carcinomas and possibly predict response to olaparib.

Tumor microenvironment-induced FOXM1 regulates ovarian cancer stemness.

In ovarian tumors, the omental microenvironment profoundly influences the behavior of cancer cells and sustains the acquisition of stem-like traits, with major impacts on tumor aggressiveness and relapse. Here, we leverage a patient-derived platform of organotypic cultures to study the crosstalk between the tumor microenvironment and ovarian cancer stem cells. We discovered that the pro-tumorigenic transcription factor FOXM1 is specifically induced by the microenvironment in ovarian cancer stem cells, through activation of FAK/YAP signaling. The microenvironment-induced FOXM1 sustains stemness, and its inactivation reduces cancer stem cells survival in the omental niche and enhances their response to the PARP inhibitor Olaparib. By unveiling the novel role of FOXM1 in ovarian cancer stemness, our findings highlight patient-derived organotypic co-cultures as a powerful tool to capture clinically relevant mechanisms of the microenvironment/cancer stem cells crosstalk, contributing to the identification of tumor vulnerabilities.

Regulator of G-protein signaling 5 (RGS5) protein: a novel marker of cancer vasculature elicited and sustained by the tumor's proangiogenic microenvironment.

We previously identified regulator of G-protein signaling 5 (RGS5) among several genes expressed by tumor-derived endothelial cells (EC). In this study, we provide the first in vivo/ex vivo evidence of RGS5 protein in the vasculature of ovarian carcinoma clinical specimens and its absence in human ovaries. Consistent with this, we show higher amounts of Rgs5 transcript in EC isolated from human cancers (as opposed to normal tissues) and demonstrate that expression is sustained by a milieu of factors typical of the proangiogenic tumor environment, including vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF-2). Supporting these findings, we show elevated levels of Rgs5 mRNA in the stroma from strongly (as opposed to weakly) angiogenic ovarian carcinoma xenografts and accordingly, we also show more of the protein associated to the abnormal vasculature. RGS5 protein predominantly colocalizes with the endothelium expressing platelet/endothelial cell adhesion molecule-1 (PECAM-1/CD31) and to a much lesser extent with perivascular/mural cells expressing platelet-derived growth factor receptor-beta (PDGFR-ß) or alpha smooth muscle actin (αSMA). To toughen the relevance of the findings, we demonstrate RGS5 in the blood vessels of other cancer models endowed with a proangiogenic environment, such as human melanoma and renal carcinoma xenografts; to the contrary, it was undetectable in the vasculature of normal mouse tissues. RGS5 expression by the cancer vasculature triggered and retained by the proangiogenic microenvironment supports its exploitation as a novel biomarker and opens the path to explore new possibilities of therapeutic intervention aimed at targeting tumor blood vessels.

The PARP1 Inhibitor AZD5305 Impairs Ovarian Adenocarcinoma Progression and Visceral Metastases in Patient-derived Xenografts Alone and in Combination with Carboplatin.

PARP inhibitors (PARPi) have changed the management of patients with ovarian cancer and their effectiveness has been demonstrated especially in homologous recombination repair-deficient tumors. These first-generation drugs target PARP1, but also PARP2 and other family members potentially responsible for adverse effects that limit their therapeutic potential and restrict their use in combination with chemotherapeutic agents. We investigated ovarian cancer patient-derived xenografts (OC-PDXs) to assess whether malignant progression could be impaired by a novel inhibitor selective for PARP1 (AZD5305) and to assess the potential of its combination with carboplatin (CPT), the standard-of-care for patients with ovarian cancer. In BRCA-mutated OC-PDXs, AZD5305 achieved greater tumor regressions and longer duration of response as well as a superior impairment of visceral metastasis and improved survival benefit compared with the first-generation dual PARP1/2 inhibitors. The combination of AZD5305 plus CPT was more efficacious than single agents. Subcutaneously growing tumors experienced regression that persisted after therapy stopped. Combination efficacy was greater against tumors that did not respond well to platinum, even at a dose at which AZD5305 monotherapy was ineffective. The combination therapy impaired metastatic dissemination and significantly prolonged the lifespan of mice bearing OC-PDXs in their abdomen. This combination benefit was evident even when CPT was used at suboptimal doses, and was superior to full-dose platinum treatment. These preclinical studies demonstrate that the PARP1-selective inhibitor AZD5305 retains and improves the therapeutic benefit of the first-generation PARPi, providing an opportunity to maximize benefits for this class of anticancer agents. Significance: Selective PARP1i AZD5305 can exceed the efficacy of first-generation PARPi, which target both PARP1 and PARP2, and potentiates the efficacy of CPT when given in combination. AZD5305 alone or in combination with platinum delayed visceral metastasis, ultimately extending the lifespan of OC-PDX-bearing mice. These preclinical models mimic the progression of the disease occurring in patients after debulking surgery, and are translationally relevant.

Fibronectin fragments generated by pancreatic trypsin act as endogenous inhibitors of pancreatic tumor growth.

BACKGROUND: The pancreatic microenvironment has a defensive role against cancer but it can acquire tumor-promoting properties triggered by multiple mechanisms including alterations in the equilibrium between proteases and their inhibitors. The identification of proteolytic events, targets and pathways would set the basis for the design of new therapeutic approaches. METHODS AND RESULTS: Here we demonstrate that spheroids isolated from human and murine healthy pancreas and co-transplanted orthotopically with pancreatic ductal adenocarcinoma (PDAC) in mouse pancreas inhibited tumor growth. The effect was mediated by trypsin-generated fibronectin (FN) fragments released by pancreatic spheroids. Tumor inhibition was observed also in a model of acute pancreatitis associated with trypsin activation. Mass spectrometry proteomic analysis of fragments and mAb against different FN epitopes identified the FN type III domain as responsible for the activity. By inhibiting integrin α5ß1, FAK and FGFR1 signaling, the fragments induced tumor cell detachment and reduced cell proliferation. Consistent with the mutual relationship between the two pathways, FGF2 restored both FGFR1 and FAK signaling and promoted PDAC cell adhesion and proliferation. FAK and FGFR inhibitors additively inhibited PDAC growth in vitro and in orthotopic in vivo models. CONCLUSIONS: This study identifies a novel role for pancreatic trypsin and fibronectin cleavage as a mechanism of protection against cancer by the pancreatic microenvironment. The finding of a FAK-FGFR cross-talk in PDAC support the combination of FAK and FGFR inhibitors for PDAC treatment to emulate the protective effect of the normal pancreas against cancer.

Chemotherapy-induced neutropenia elicits metastasis formation in mice by promoting proliferation of disseminated tumor cells.

Chemotherapy is the standard of care for most malignancies. Its tumor debulking effect in adjuvant or neoadjuvant settings is unquestionable, although secondary effects have been reported that paradoxically promote metastasis. Chemotherapy affects the hematopoietic precursors leading to myelosuppression, with neutropenia being the main hematological toxicity induced by cytotoxic therapy. We used renal and lung murine tumor models metastatic to the lung to study chemotherapy-induced neutropenia (CIN) in the metastatic process. Cyclophosphamide and doxorubicin, two myelosuppressive drugs, but not cisplatin, increased the burden of artificial metastases to the lung, by reducing neutrophils. This effect was recapitulated by treatment with anti-Ly6G, the selective antibody-mediated neutrophil depletion that unleashed the formation of lung metastases in both artificial and spontaneous metastasis settings. The increased cancer dissemination was reversed by granulocyte-colony stimulating factor-mediated boosting of neutrophils in combination with chemotherapy. CIN affected the early metastatic colonization of the lung, quite likely promoting the proliferation of tumor cells extravasated into the lung at 24-72 hours. CIN did not affect the late events of the metastatic process, with established metastasis to the lung, nor was there any effect on the release of cancer cells from the primary, whose growth was, in fact, somewhat inhibited. This work suggests a role of neutrophils associated to a common cancer treatment side effect and claims a deep dive into the relationship between chemotherapy-induced neutropenia and metastasis.

Differential vascular expression and regulation of oncofetal tenascin-C and fibronectin variants in renal cell carcinoma (RCC): implications for an individualized angiogenesis-related targeted drug delivery.

The study was aimed at determining the vascular expression of oncofetal fibronectin (oncfFn) and tenascin-C (oncfTn-C) isoforms in renal cell carcinoma (RCC) and its metastases which are well-known targets for antibody-based pharmacodelivery. Furthermore, the influence of tumour cells on endothelial mRNA expression of these molecules was investigated. Evaluation of vascular ED-A(+) and ED-B(+) Fn as well as A1(+) and C(+) Tn-C was performed after immunofluorescence double and triple staining using human recombinant antibodies on clear cell, papillary and chromophobe primary RCC and metastases. The influence of hypoxic RCC-conditioned medium on oncfFn and oncfTn-C mRNA expression was examined in human umbilical vein endothelial cells (HUVEC) by real time RT-PCR. There are RCC subtype specific expression profiles of vascular oncfFn and oncfTn-C and corresponding patterns when comparing primary tumours and metastases. Within one tumour, there are different vessel populations with regard to the incorporation of oncfTn-C and oncfFn into the vessel wall. In vitro tumour-derived soluble mediators induce an up regulation of oncfTn-C and oncfFn mRNA in HUVEC which can be blocked by Avastin(®). Vascular expression of oncFn and oncTn-C variants depends on RCC subtype and may reflect an individual tumour stroma interaction or different stages of vessel development. Therefore, oncFn or oncTn-C variants can be suggested as molecular targets for individualized antibody based therapy strategies in RCC. Tumour-derived VEGF could be shown to regulate target expression.

Endoplasmic reticulum oxidoreductin 1-alpha deficiency and activation of protein translation synergistically impair breast tumour resilience.

BACKGROUND AND PURPOSE: Endoplasmic reticulum (ER) stress triggers an adaptive response in tumours which fosters cell survival and resilience to stress. Activation of the ER stress response, through its PERK branch, promotes phosphorylation of the α-subunit of the translation initiation factor eIF2, thereby repressing general protein translation and augmenting the translation of ATF4 with the downstream CHOP transcription factor and the protein disulfide oxidase, ERO1-alpha EXPERIMENTAL APPROACH: Here, we show that ISRIB, a small molecule that inhibits the action of phosphorylated eIF2alpha, activating protein translation, synergistically interacts with the genetic deficiency of protein disulfide oxidase ERO1-alpha, enfeebling breast tumour growth and spread. KEY RESULTS: ISRIB represses the CHOP signal, but does not inhibit ERO1. Mechanistically, ISRIB increases the ER protein load with a marked perturbing effect on ERO1-deficient triple-negative breast cancer cells, which display impaired proteostasis and have adapted to a low client protein load in hypoxia, and ERO1 deficiency impairs VEGF-dependent angiogenesis. ERO1-deficient triple-negative breast cancer xenografts have an augmented ER stress response and its PERK branch. ISRIB acts synergistically with ERO1 deficiency, inhibiting the growth of triple-negative breast cancer xenografts by impairing proliferation and angiogenesis. CONCLUSION AND IMPLICATIONS: These results demonstrate that ISRIB together with ERO1 deficiency synergistically shatter the PERK-dependent adaptive ER stress response, by restarting protein synthesis in the setting of impaired proteostasis, finally promoting tumour cytotoxicity. Our findings suggest two surprising features in breast tumours: ERO1 is not regulated via CHOP under hypoxic conditions, and ISRIB offers a therapeutic option to efficiently inhibit tumour progression in conditions of impaired proteostasis.

The DNA-PK Inhibitor AZD7648 Sensitizes Patient-Derived Ovarian Cancer Xenografts to Pegylated Liposomal Doxorubicin and Olaparib Preventing Abdominal Metastases.

Ovarian cancer is the deadliest gynecologic cancer, with a 5-year survival rate of 30%, when the disease has spread throughout the peritoneal cavity. We investigated the efficacy to delay disease progression by the DNA-dependent protein kinase (DNA-PK) inhibitor AZD7648, administered in combination with two of the therapeutic options for patient management: either pegylated liposomal doxorubicin (PLD) or the PARP inhibitor olaparib. Patient-derived ovarian cancer xenografts (OC-PDX) were transplanted subcutaneously to evaluate the effect of treatment on tumor growth, or orthotopically in the peritoneal cavity to evaluate the effect on metastatic spread. AZD7648 was administered orally in combination with PLD (dosed intravenously) or with olaparib (orally). To prove the inhibition of DNA-PK in the tumors, we measured pDNA-PKcs, pRPA32, and γH2AX, biomarkers of DNA-PK activity. AZD7648 enhanced the therapeutic efficacy of PLD in all the OC-PDXs tested, regardless of their BRCA status or sensitivity to cisplatin or PLD. The treatment caused disease stabilization, which persisted despite therapy discontinuation for tumors growing subcutaneously, and significantly impaired the abdominal metastatic dissemination, prolonging the lifespan of mice implanted orthotopically. AZD7648 potentiated the efficacy of olaparib in BRCA-deficient OC-PDXs but did not sensitize BRCA-proficient OC-PDXs to olaparib, despite an equivalent inhibition of DNA-PK, suggesting the need of a preexisting olaparib activity to benefit from the addition of AZD7648. This work suggests that AZD7648, an inhibitor of DNA-PK, dosed in combination with PLD or olaparib is an exciting therapeutic option that could benefit patients with ovarian cancer and should be explored in clinical trials.

PGC1α/ß Expression Predicts Therapeutic Response to Oxidative Phosphorylation Inhibition in Ovarian Cancer.

Ovarian cancer is the deadliest gynecologic cancer, and novel therapeutic options are crucial to improve overall survival. Here we provide evidence that impairment of oxidative phosphorylation (OXPHOS) can help control ovarian cancer progression, and this benefit correlates with expression of the two mitochondrial master regulators PGC1α and PGC1ß. In orthotopic patient-derived ovarian cancer xenografts (OC-PDX), concomitant high expression of PGC1α and PGC1ß (PGC1α/ß) fostered a unique transcriptional signature, leading to increased mitochondrial abundance, enhanced tricarboxylic acid cycling, and elevated cellular respiration that ultimately conferred vulnerability to OXPHOS inhibition. Treatment with the respiratory chain complex I inhibitor IACS-010759 caused mitochondrial swelling and ATP depletion that consequently delayed malignant progression and prolonged the lifespan of high PGC1α/ß-expressing OC-PDX-bearing mice. Conversely, low PGC1α/ß OC-PDXs were not affected by IACS-010759, thus pinpointing a selective antitumor effect of OXPHOS inhibition. The clinical relevance of these findings was substantiated by analysis of ovarian cancer patient datasets, which showed that 25% of all cases displayed high PGC1α/ß expression along with an activated mitochondrial gene program. This study endorses the use of OXPHOS inhibitors to manage ovarian cancer and identifies the high expression of both PGC1α and ß as biomarkers to refine the selection of patients likely to benefit most from this therapy. SIGNIFICANCE: OXPHOS inhibition in ovarian cancer can exploit the metabolic vulnerabilities conferred by high PGC1α/ß expression and offers an effective approach to manage patients on the basis of PGC1α/ß expression.

Non-peptidic thrombospondin-1 mimics as fibroblast growth factor-2 inhibitors: an integrated strategy for the development of new antiangiogenic compounds.

Endogenous inhibitors of angiogenesis, such as thrombospondin-1 (TSP-1), are promising sources of therapeutic agents to treat angiogenesis-driven diseases, including cancer. TSP-1 regulates angiogenesis through different mechanisms, including binding and sequestration of the angiogenic factor fibroblast growth factor-2 (FGF-2), through a site located in the calcium binding type III repeats. We hypothesized that the FGF-2 binding sequence of TSP-1 might serve as a template for the development of inhibitors of angiogenesis. Using a peptide array approach followed by binding assays with synthetic peptides and recombinant proteins, we identified a FGF-2 binding sequence of TSP-1 in the 15-mer sequence DDDDDNDKIPDDRDN. Molecular dynamics simulations, taking the full flexibility of the ligand and receptor into account, and nuclear magnetic resonance identified the relevant residues and conformational determinants for the peptide-FGF interaction. This information was translated into a pharmacophore model used to screen the NCI2003 small molecule databases, leading to the identification of three small molecules that bound FGF-2 with affinity in the submicromolar range. The lead compounds inhibited FGF-2-induced endothelial cell proliferation in vitro and affected angiogenesis induced by FGF-2 in the chicken chorioallantoic membrane assay. These small molecules, therefore, represent promising leads for the development of antiangiogenic agents. Altogether, this study demonstrates that new biological insights obtained by integrated multidisciplinary approaches can be used to develop small molecule mimics of endogenous proteins as therapeutic agents.

Tumor vascular remodeling by thrombospondin-1 enhances drug delivery and antineoplastic activity.

The disorganized and inefficient tumor vasculature is a major obstacle to the delivery and efficacy of antineoplastic treatments. Antiangiogenic agents can normalize the tumor vessels, improving vessel function and boosting the distribution and activity of chemotherapy. The type III repeats (T3R) domain of thrombospondin-1 contains different potential antiangiogenic sequences. We therefore hypothesized that it might affect the tumor vasculature. Ectopic expression of the T3R domain by the tumor cells or by the host, or administration of recombinant T3R, delayed the in vivo growth of experimental tumors. Tumors presented marked reorganization of the vasculature, with abundant but smaller vessels, associated with substantially less necrosis. Mechanistically, the use of truncated forms of the domain, containing different active sequences, pointed to the FGF2/FGFR/ERK axis as a target for T3R activity. Along with reduced necrosis, the expression of T3R promoted tumor distribution of chemotherapy (paclitaxel), with a higher drug concentration and more homogeneous distribution, as assessed by HPLC and MALDI imaging mass spectrometry. T3R-expressing tumors were more responsive to paclitaxel and cisplatin. This study shows that together with its known role as a canonical inhibitor of angiogenesis, thrombospondin-1 can also remodel tumor blood vessels, affecting the morphological and functional properties of the tumor vasculature. The ability of T3R to reduce tumor growth and improve the response to chemotherapy opens new perspectives for therapeutic strategies based on T3R to be used in combination therapies.