The role of tumor microenvironment in resistance to anti-angiogenic therapy

The application of nanoparticles in delivering small RNAs for cancer therapy

Small molecular RNAs, including microRNA (miRNA) and small interfering RNA (siRNA), participate in the regulation of gene expression. As powerful regulators, miRNAs, take part in posttranscriptional regulation of gene expression and play important roles in the diagnosis and treatment of cancer. Meanwhile, siRNA can induce sequence-specific gene silencing, thus being able to inhibit tumorigenesis by suppressing the expression of their targeted proto-oncogenes. Small RNAs (including naked miRNAs and siRNAs) are easily degraded by circulating RNAase, which can be retarded through the package of nanoparticles. Therefore, nanoparticles help tumor therapy by regulating targeted genes of small RNAs. Here, we reviewed the effects of small RNAs on gene expression; the advantages, disadvantages, and targeted modification of nanoparticles as carriers transporting small RNAs; and the application of nanocarriers delivering small RNA for cancer-targeted therapy.

A Splice Form of VEGF, a Potential Anti-Angiogenetic Form of Head and Neck Squamous Cell Cancer Inhibition

Angiogenesis, primarily mediated by vascular endothelial growth factor (VEGF), is a fundamental step in the progression and metastasis of head and neck squamous cell carcinoma (HNSCC). Traditional anti-angiogenic therapies that target the VEGF pathway have shown promise but are often associated with significant side effects and variable efficacy due to the complexity of the angiogenic signaling pathway. This review highlights the potential of a specific VEGF splice form, VEGF165b, as an innovative therapeutic target for HNSCC. VEGF165b, unlike standard VEGF, is a natural inhibitor that binds to VEGF receptors without triggering pro-angiogenic signaling. Its distinct molecular structure and behavior suggest ways to modulate angiogenesis. This concept is particularly relevant when studying HNSCC, as introducing VEGF165b's anti-angiogenic properties offers a novel approach to understanding and potentially influencing the disease's dynamics. The review synthesizes experimental evidence suggesting the efficacy of VEGF165b in inhibiting tumor-induced angiogenesis and provides insight into a novel therapeutic strategy that could better manage HNSCC by selectively targeting aberrant vascular growth. This approach not only provides a potential pathway for more targeted and effective treatment options but also opens the door to a new paradigm in anti-angiogenic therapy with the possibility of reduced systemic toxicity. Our investigation is reshaping the future of HNSCC treatment by setting the stage for future research on VEGF splice variants as a tool for personalized medicine.

Remodeling of tumor microenvironment by extracellular matrix protein 1a differentially regulates ovarian cancer metastasis

We previously reported that extracellular matrix protein 1 isoform a (ECM1a) promotes epithelial ovarian cancer (EOC) through autocrine signaling by binding to cell surface receptors αXβ2. However, the role of ECM1a as a secretory molecule in the tumor microenvironment is rarely reported. In this study, we constructed murine Ecm1-knockout mice and human ECM1a-knockin mice and further generated orthotopic or peritoneal xenograft tumor models to mimic the different metastatic stages of EOC. We show that ECM1a induces oncogenic metastasis of orthotopic xenograft tumors, but inhibits early-metastasis of peritoneal xenograft tumors. ECM1a remodels extracellular matrices (ECM) and promotes remote metastases by recruiting and transforming bone marrow mesenchymal stem cells (BMSCs) into platelet-derived growth factor receptor beta (PDGFRβ+) cancer-associated fibroblasts (CAFs) and facilitating the secretion of angiopoietin-like protein 2 (ANGPTL2). Competing with ECM1a, ANGPTL2 also binds to integrin αX through the P1/P2 peptides, resulting in negative effects on BMSC differentiation. Collectively, this study reveals the dual functions of ECM1a in remodeling of TME during tumor progression, emphasizing the complexity of EOC phenotypic heterogeneity and metastasis.

Unraveling the tumor microenvironment: Insights into cancer metastasis and therapeutic strategies

This comprehensive review delves into the pivotal role of the tumor microenvironment (TME) in cancer metastasis and therapeutic response, offering fresh insights into the intricate interplay between cancer cells and their surrounding milieu. The TME, a dynamic ecosystem comprising diverse cellular and acellular elements, not only fosters tumor progression but also profoundly affects the efficacy of conventional and emerging cancer therapies. Through nuanced exploration, this review illuminates the multifaceted nature of the TME, elucidating its capacity to engender drug resistance via mechanisms such as hypoxia, immune evasion, and the establishment of physical barriers to drug delivery. Moreover, it investigates innovative therapeutic approaches aimed at targeting the TME, including stromal reprogramming, immune microenvironment modulation, extracellular matrix (ECM)-targeting agents, and personalized medicine strategies, highlighting their potential to augment treatment outcomes. Furthermore, this review critically evaluates the challenges posed by the complexity and heterogeneity of the TME, which contribute to variable therapeutic responses and potentially unintended consequences. This underscores the need to identify robust biomarkers and advance predictive models to anticipate treatment outcomes, as well as advocate for combination therapies that address multiple facets of the TME. Finally, the review emphasizes the necessity of an interdisciplinary approach and the integration of cutting-edge technologies to unravel the intricacies of the TME, thereby facilitating the development of more effective, adaptable, and personalized cancer treatments. By providing critical insights into the current state of TME research and its implications for the future of oncology, this review highlights the dynamic and evolving landscape of this field.

Angiogenesis and Pancreatic Cancer: Novel Approaches to Overcome Treatment Resistance

Pancreatic cancer (PCa) is acknowledged as a significant contributor to global cancer- related mortality and is widely recognized as one of the most challenging malignant diseases to treat. Pancreatic ductal adenocarcinoma (PDAC), which is the most common type of PCa, is highly aggressive and is mostly incurable. The poor prognosis of this neoplasm is exacerbated by the prevalence of angiogenic molecules, which contribute to stromal stiffness and immune escape. PDAC overexpresses various proangiogenic proteins, including vascular endothelial growth factor (VEGF)-A, and the levels of these molecules correlate with poor prognosis and treatment resistance. Moreover, VEGF-targeting anti-angiogenesis treatments are associated with the onset of resistance due to the development of hypoxia, which in turn induces the production of angiogenic molecules. Furthermore, excessive angiogenesis is one of the hallmarks of the second most common form of PCa, namely, pancreatic neuroendocrine tumor (PNET). In this review, the role of angiogenesis regulators in promoting disease progression in PCa, and the impact of these molecules on resistance to gemcitabine and various therapies against PCa are discussed. Finally, the use of anti-angiogenic agents in combination with chemotherapy and other targeted therapeutic molecules is discussed as a novel solution to overcome current treatment limitations in PCa.

Therapeutic targeting of angiopoietins in tumor angiogenesis and cancer development

The formation and progression of tumors in humans are linked to the abnormal development of new blood vessels known as neo-angiogenesis. Angiogenesis is a broad word that encompasses endothelial cell migration, proliferation, tube formation, and intussusception, as well as peri-EC recruitment and extracellular matrix formation. Tumor angiogenesis is regulated by angiogenic factors, out of which some of the most potent angiogenic factors such as vascular endothelial growth factor and Angiopoietins (ANGs) in the body are produced by macrophages and other immune cells within the tumor microenvironment. ANGs have a distinct function in tumor angiogenesis and behavior. ANG1, ANG 2, ANG 3, and ANG 4 are the family members of ANG out of which ANG2 has been extensively investigated owing to its unique role in modifying angiogenesis and its tight association with tumor progression, growth, and invasion/metastasis, which makes it an excellent candidate for therapeutic intervention in human malignancies. ANG modulators have demonstrated encouraging outcomes in the treatment of tumor development, either alone or in conjunction with VEGF inhibitors. Future development of more ANG modulators targeting other ANGs is needed. The implication of ANG1, ANG3, and ANG4 as probable therapeutic targets for anti-angiogenesis treatment in tumor development should be also evaluated. The article has described the role of ANG in tumor angiogenesis as well as tumor growth and the treatment strategies modulating ANGs in tumor angiogenesis as demonstrated in clinical studies. The pharmacological modulation of ANGs and ANG-regulated pathways that are responsible for tumor angiogenesis and cancer development should be evaluated for the development of future molecular therapies.

Extracellular vesicles targeting tumor microenvironment in ovarian cancer

Ovarian cancer (OC) is a prevalent neoplastic condition affecting women. Extracellular vesicles (EVs), nano-sized membrane vesicles, are secreted by various cells in both physiological and pathological states. The profound interplay between EVs and the tumor microenvironment (TME) in ovarian cancer is crucial. In this review, we explores the pivotal role of EVs in facilitating intercellular communication between cancer cells and the TME, emphasizing the potential of EVs as promising diagnostic markers and innovative therapeutic targets for ovarian cancer. The comprehensive analysis outlines the specific mechanisms by which EVs engage in communication with the constituents of the TME, including the modulation of tumor growth through EVs carrying matrix metalloproteinases (MMPs) and EV-mediated inhibition of angiogenesis, among other factors. Additionally, the we discuss the potential clinical applications of EVs that target the TME in ovarian cancer, encompassing the establishment of novel treatment strategies and the identification of novel biomarkers for early detection and prognosis. Finally, this review identifies novel strategies for therapeutic interventions, such as utilizing EVs as carriers for drug delivery and targeting specific EV-mediated signaling pathways. In summary, this manuscript offers valuable insights into the role of EVs in ovarian cancer and highlights the significance of comprehending intercellular communication in the realm of cancer biology.

Enhanced antitumor and anti-metastasis by VEGFR2-targeted doxorubicin immunoliposome synergy with NK cell activation

Liposomal doxorubicin exhibits stronger drug accumulation at the tumor site due to the Enhanced Permeability and Retention (EPR) effect. However, the prognosis for the patient is poor due to this drug's lack of targeting and tumor metastasis during treatment. Vascular epidermal growth factor receptor (VEGFR2) plays an important role in angiogenesis and cancer metastasis. To enhance antitumor efficacy of PEGylated liposomal doxorubicin, we constructed a VEGFR2-targeted and doxorubicin-loaded immunoliposome (Lipo-DOX-C00) by conjugating a VEGFR2-specific, single chain antibody fragment to DSPE-PEG2000-MAL, and then we inserted the antibody-conjugated polymer into liposomal doxorubicin (Lipo-DOX). The immunoliposome was formed uniformly with high affinity for VEGFR2. In vitro, Lipo-DOX-C00 enhanced doxorubicin internalization into LLC and 4T1 cells compared with non-conjugated, liposomal doxorubicin. In vivo, Lipo-DOX-C00 delivered DOX to tumor tissues effectively, which exhibited an improved antitumor and anti-metastasis efficacy in both LLC subcutaneous tumor models and 4T1 tumor models. In addition, the combined therapy of a VEGFR2-MICA bispecific antibody (JZC01) and Lipo-DOX-C00 achieved enhanced inhibition of cancer growth and metastasis due to activation of the immune system. Our study provides a promising approach to clinical application of liposomal doxorubicin.

The sialyl-Tn antigen synthase genes regulates migration-proliferation dichotomy in prostate cancer cells under hypoxia

A low-oxygen (hypoxia) tumor microenvironment can facilitate chemotherapy and radiation therapy resistance in tumors and is associated with a poor prognosis. Hypoxia also affects PCa (prostate cancer) phenotype transformation and causes therapeutic resistance. Although O-glycans are known to be involved in the malignancy of various cancers under hypoxia, the expression and function of O-glycans in PCa are not well understood. In this study, the saccharide primer method was employed to analyze O-glycan expression in PCa cells. Results showed that the expression of sTn antigens was increased in PCa cells under hypoxia. Furthermore, it was found that ST6GalNAc1, the sTn antigen synthase gene, was involved in the migration-proliferation dichotomy and drug resistance in PCa cells under hypoxia. The results of this study will contribute to the development of novel diagnostic markers and drug targets for PCa under hypoxia.

CAF signature predicts the prognosis of colorectal cancer patients: A retrospective study based on bulk RNA sequencing and single-cell RNA sequencing data

The incidence rate and mortality rate of colorectal cancer (CRC) ranks third and second globally. Cancer-associated fibroblasts (CAFs) are the major constituent of the stromal cells in the tumor microenvironment (TME) and are closely associated with patients' prognoses. Our study intended to establish a prognostic model for CRC using hallmark genes of CAFs. The expression values of genes and clinicopathological characteristics of patients were enrolled from the cancer genome atlas database as well as the gene expression omnibus database. The single-cell RNA sequencing data were collected and analyzed in the deeply integrated human single-cell omics database and cancer single-cell expression map databases. The ESTIMATE algorithm was applied to access the infiltration levels of immune and stromal cells. The prognostic genes were selected by the Cox regression analysis and the prognostic signature was constructed by the least absolute shrinkage and selection operator algorithm. gene set enrichment analysis was used to explore the enriched gene sets. In this study, based on bulk RNA sequencing and single-cell RNA sequencing data, and we found that more CAFs were infiltrated in the tumor microenvironment and consisted of 3 subtypes. Then we constructed a prognostic signature for CRC using hallmark genes of CAFs and proved that this signature exhibited high values to predict the overall survival of CRC patients in independent training and validating cohorts. Besides, function enrichment analysis revealed that our prognostic model was significantly associated with immune regulation. Further analysis showed that the infiltrated levels of tumor-suppressing immune cells and the expression of higher immune checkpoint genes in CRC tissues were higher in patients with high-risk scores. Furthermore, immunohistochemistry analysis exhibited that these genes in our prognostic signature were markedly upregulated in CRC tissues. We first constructed a signature based on CAFs hallmark genes to predict the survival of CRC patients and further revealed that the tumor-suppressing microenvironment and dysregulated immune checkpoint genes in CRC tissues were partly responsible for the poor prognosis of patients.

The roles of metabolic profiles and intracellular signaling pathways of tumor microenvironment cells in angiogenesis of solid tumors

Innate and adaptive immune cells patrol and survey throughout the human body and sometimes reside in the tumor microenvironment (TME) with a variety of cell types and nutrients that may differ from those in which they developed. The metabolic pathways and metabolites of immune cells are rooted in cell physiology, and not only provide nutrients and energy for cell growth and survival but also influencing cell differentiation and effector functions. Nowadays, there is a growing awareness that metabolic processes occurring in cancer cells can affect immune cell function and lead to tumor immune evasion and angiogenesis. In order to safely treat cancer patients and prevent immune checkpoint blockade-induced toxicities and autoimmunity, we suggest using anti-angiogenic drugs solely or combined with Immune checkpoint blockers (ICBs) to boost the safety and effectiveness of cancer therapy. As a consequence, there is significant and escalating attention to discovering techniques that target metabolism as a new method of cancer therapy. In this review, a summary of immune-metabolic processes and their potential role in the stimulation of intracellular signaling in TME cells that lead to tumor angiogenesis, and therapeutic applications is provided. Video abstract.

Apatinib plus vinorelbine versus vinorelbine for metastatic triple-negative breast cancer who failed first/second-line treatment: the NAN trial

While therapies such as chemotherapy combined with immunotherapy, sacituzumab govitecan, and PARP inhibitors are available for metastatic TNBC, on disease progression after these therapies, the mainstay of therapy is chemotherapy. Apatinib is a small-molecule tyrosine kinase inhibitor that has promising anti-angiogenesis and antitumor activity for TNBC. We aimed to evaluate the safety and efficacy of adding apatinib to chemotherapy in patients with advanced TNBC with failed first/second-line treatment. A total of 66 patients were randomly assigned, in a 1:1 ratio, to receive vinorelbine or vinorelbine with apatinib in 28-day cycles. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), overall response rate (ORR) and safety. 33 received apatinib plus vinorelbine and 32 received vinorelbine (1 was withdrawal). Median PFS was significantly longer in the apatinib plus vinorelbine group than in the vinorelbine group (3.9 months vs. 2.0 months; hazard ratio, 1.82; 95% confidence interval [CI], 1.06 to 3.11; P = 0.026). Median OS was 11.5 months with apatinib plus vinorelbine and 9.9 months with vinorelbine (HR,1.01; 95% CI, 0.51 to 1.97; P = 0.985). The ORR was 9.1% in the apatinib plus vinorelbine group and 6.3% in the vinorelbine group (P = 0.667). The most common treatment-related hematologic grade 3–4 adverse events in apatinib plus vinorelbine group, were leukopenia, granulocytopenia, anemia, and thrombocytopenia. no treatment-related nonhematologic grade 4 adverse events or treatment-related deaths were observed. Collectively, adding apatinib to vinorelbine shows a promising benefit in PFS compared to vinorelbine monotherapy, with an excellent toxicity profile, warranting further exploration.

Reassessing vascular endothelial growth factor (VEGF) in anti-angiogenic cancer therapy

Vascularization is fundamental to the growth and spread of tumor cells to distant sites. As a consequence, angiogenesis, the sprouting of new blood vessels from existing ones, is a characteristic trait of cancer. In 1971, Judah Folkman postulated that tumour growth is angiogenesis dependent and that by cutting off blood supply, a neoplastic lesion could be potentially starved into remission. Decades of research have been devoted to understanding the role that vascular endothelial growth factor (VEGF) plays in tumor angiogenesis, and it has been identified as a significant pro-angiogenic factor that is frequently overexpressed within a tumor mass. Today, anti-VEGF drugs such as Sunitinib, Sorafenib, Axitinib, Tanibirumab, and Ramucirumab have been approved for the treatment of advanced and metastatic cancers. However, anti-angiogenic therapy has turned out to be more complex than originally thought. The failure of this therapeutic option calls for a reevaluation of VEGF as the major target in anti-angiogenic cancer therapy. The call for reassessment is based on two rationales: first, tumour blood vessels are abnormal, disorganized, and leaky; this not only prevents optimal drug delivery but it also promotes hypoxia and metastasis; secondly, tumour growth or regrowth might be blood vessel dependent and not angiogenesis dependent as tumour cells can acquire blood vessels via non-angiogenic mechanisms. Therefore, a critical assessment of VEGF, VEGFRs, and their inhibitors could glean newer options such as repurposing anti-VEGF drugs as vascular normalizing agents to enhance drug delivery of immune checkpoint inhibitors.

VEGF‑mediated tumour growth and EMT in 2D and 3D cell culture models of hepatocellular carcinoma

The purpose of the present study was to evaluate the effects of vascular endothelial growth factor (VEGF) on tumorigenic properties in two-dimensional (2D) and three-dimensional (3D) cultures of hepatoma cells. The proliferation and invasion of hepatoma cells was assessed using wound healing, chemotaxis Transwell, invasion, tube-forming and hanging drop assays in both 2D and 3D cultures. The expression levels of epithelial-mesenchymal transition (EMT) and stemness markers were analysed using reverse transcription-quantitative PCR (RT-qPCR) for mRNA expression and immunofluorescence assay for protein expression. To validate the role of VEGF in tumour growth, a VEGF receptor (VEGFR) inhibitor (sorafenib) was used. The results demonstrated that the hepatoma cells formed 3D spheroids that differed in size and density in the absence and presence of the growth factor, VEGF. In all spheroids, invasion and angiogenesis were more aggressive in 3D cultures in comparison to 2D conditions following treatment with VEGF. Mechanistically, the VEGF-mediated increase in the levels of EMT markers, including Vimentin, N-cadherin 2 (Cadherin 2) and Thy-1 Cell Surface Antigen was observed in the 2D and 3D cultures. Sorafenib treatment for 24 h culminated in a marked reduction in cell migration, cell-cell adhesion, spheroid compaction and EMT gene expression in 3D models as compared to the 2D models. On the whole, the findings of the present study suggested that as compared to the 2D cell cultures, 3D cell cultures model may be used as a more realistic model for the study of tumour growth and invasion in the presence of angiogenic factors, as well as for tumour inhibitor screening.

Augmenting Experimental Gastric Cancer Activity of Irinotecan through Liposomal Formulation and Antiangiogenic Combination Therapy

Gastric adenocarcinoma (GAC) is the third most common cause of cancer-related deaths worldwide. Combination chemotherapy remains the standard treatment for advanced GAC. Liposomal irinotecan (nal-IRI) has improved pharmacokinetics (PK) and drug biodistribution compared with irinotecan (IRI, CPT-11). Angiogenesis plays a crucial role in the progression and metastasis of GAC. We evaluated the antitumor efficacy of nal-IRI in combination with novel antiangiogenic agents in GAC mouse models. Animal survival studies were performed in peritoneal dissemination xenografts. Tumor growth and PK studies were performed in subcutaneous xenografts. Compared with controls, extension in animal survival by nal-IRI and IRI was >156% and >94%, respectively. The addition of nintedanib or DC101 extended nal-IRI response by 13% and 15%, and IRI response by 37% and 31% (MKN-45 xenografts); nal-IRI response by 11% and 3%, and IRI response by 16% and 40% (KATO-III xenografts). Retardation of tumor growth was greater with nal-IRI (92%) than IRI (71%). Nintedanib and DC101 addition tend to augment nal-IRI or IRI response in this model. The addition of antiangiogenic agents enhanced tumor cell proliferation inhibition effects of nal-IRI or IRI. The tumor vasculature was decreased by nintedanib (65%) and DC101 (58%), while nal-IRI and IRI alone showed no effect. PK characterization in GAC xenografts demonstrated that compared with IRI, nal-IRI treatment groups had higher retention, circulation time, and tumor levels of CPT-11 and its active metabolite SN-38. These findings indicate that nal-IRI, alone and in combination with antiangiogenic agents, has the potential for improving clinical GAC therapy.

Microphysiological model of the renal cell carcinoma to inform anti-angiogenic therapy

Renal cell carcinomas are common genitourinary tumors characterized by high vascularization and strong reliance on glycolysis. Despite the many available therapies for renal cell carcinomas, first-line targeted therapies, such as cabozantinib, and durable reaponses are seen in only a small percentage of patients. Yet, little is known about the mechanisms that drive response (or lack thereof). This dearth of knowledge can be explained by the dynamic and complex microenvironment of renal carcinoma, which remains challenging to recapitulate in vitro. Here, we present a microphysiological model of renal cell carcinoma, including a tubular blood vessel model of induced pluripotent stem cell-derived endothelial cells and an adjacent 3D carcinoma model. Our model recapitulated hypoxia, glycolic metabolism, and sprouting angiogenesis. Using our model, we showed that cabozantinib altered cancer cell metabolism and decreased sprouting angiogenesis but did not restore barrier function. This microphysiological model could be helpful to elucidate, through multiple endpoints, the contributions of the relevant environmental components in eliciting a functional response or resistance to therapy in renal cell carcinoma.

Targeting CCR2+ macrophages with BET inhibitor overcomes adaptive resistance to anti-VEGF therapy in ovarian cancer

Purpose

Tumor-associated macrophages (TAMs) are known to contribute to adaptive resistance to anti-vascular endothelial growth factor (VEGF) antibody (AVA) therapy in ovarian cancer. BET (bromodomain and extra-terminal domain) inhibitors (BETi) may have unique roles in targeting TAMs. Our objective was to examine the effects of BETi on TAMs, especially in the context of enhancing the efficacy of AVA therapy.

Methods

We conducted a series of in vitro (MTT assay, apoptosis, flow cytometry, and RNA sequencing) and in vivo (xenograft ovarian cancer model) experiments to determine the biological effects of BETi combined with AVA in ovarian cancer. For statistical analysis, a two-tailed Student’s t test (equal variance) or ANOVA was used for multiple groups’ comparison, and p < 0.05 was considered significant.

Results

BETi resulted in a dose-dependent decrease in cell viability and induced apoptosis (p < 0.01) in ovarian cancer cells (SKOV3ip1, OVCAR5, and OVCAR8). Treatment with BETi significantly increased apoptosis in THP-1 monocytes and macrophages (PMA-differentiated THP-1; p < 0.01). Furthermore, BETi selectively induced greater apoptosis in M2-like macrophages (PMA and IL-4, IL-13-differentiated THP-1) (31.3%-36.1%) than in M1-like macrophages (PMA and LPS-differentiated THP-1) (12.4%-18.5%) (p < 0.01). Flow cytometry revealed that the percentage of M1-like macrophages (CD68⁺/CD80⁺) was significantly increased after treatment with low-dose BETi (ABBV-075 0.1 µM; p < 0.05), whereas the percentage of CD68⁺/CCR2⁺ macrophages was significantly decreased (p < 0.001); these findings suggest that BETi may selectively inhibit the survival of CCR2⁺ macrophages and re-polarize the macrophages into an M1-like phenotype. RNA-seq analysis revealed that BETi selectively targeted macrophage infiltration-related cytokines/chemokines in ovarian cancer (adjusted p < 0.05 and Log2 fold change ≥ 1.5). Finally, using in vivo ovarian cancer models, compared with control or monotherapy, the combination of BETi (ABBV-075) and bevacizumab resulted in greater inhibition of tumor growth and macrophage infiltration (p < 0.05) and longer survival of tumor-bearing mice (p < 0.001).

Conclusions

Our findings indicate a previously unrecognized role for BETi in selectively targeting CCR2⁺ TAMs and enhancing the efficacy of AVA therapy in ovarian cancer.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00432-021-03885-z.

Cancer Stem Cells Contribute to Drug Resistance in Multiple Different Ways

Many tumors are resistant to conventional cancer therapies because a tumor is composed of heterogeneous cell population. Especially, subpopulation of cancer stem cells, which have self-renewal and differentiation properties and responsible for the tumor initiation, is generally considered resistant to chemo-, radio-, and immune therapy. Understanding the mechanism of drug resistance in cancer stem cells should lead to establish more effective therapeutic strategies. Actually, different molecular mechanisms are conceivable for cancer stem cells acquiring drug resistance. These mechanisms include not only cytoplasmic signaling pathways but also the intercellular communications in the tumor microenvironment. Recently, a great deal of successful reports challenged to elucidate the mechanisms of drug resistance and to develop novel treatments targeting cancer stem cells.

FGD5 regulates endothelial cell PI3 kinase-β to promote neo-angiogenesis

Angiogenesis is required in embryonic development and tissue repair in the adult. Vascular endothelial growth factor (VEGF) initiates angiogenesis, and VEGF or its receptor is targeted therapeutically to block pathological angiogenesis. Additional pro-angiogenic cues, such as CXCL12 acting via the CXCR4 receptor, co-operate with VEGF/VEGFR2 to cue vascular patterning. We studied the role of FGD5, an endothelial Rho GTP/GDP exchange factor (RhoGEF), to regulate CXCR4-dependent signals in the endothelial cell (EC). Patient-derived renal cell carcinomas produce a complex milieu of growth factors that stimulated sprouting angiogenesis and endothelial tip cell differentiation ex vivo that was blocked by EC FGD5 loss. In a simplified model, CXCL12 augmented sprouting and tip gene expression under conditions where VEGF was limiting. CXCL12-stimulated tip cell differentiation was dependent on PI3 kinase (PI3K)-β activity. Knockdown of EC FGD5 abolished CXCR4 signaling to PI3K-β and Akt. Further, inhibition of Rac1, a Rho GTPase required for PI3K-β activity, recapitulated the signaling defects of FGD5 deficiency, suggesting that FGD5 may regulate PI3K-β activity through Rac1. Overexpression of a RhoGEF deficient, Dbl domain-deleted FGD5 mutant reduced CXCL12-stimulated Akt phosphorylation and failed to rescue PI3K signaling in native FGD5-deficient EC, indicating that FGD5 RhoGEF activity is required for FDG5 function. Endothelial expression of mutant PI3K-β with an inactivated Rho binding domain confirmed that CXCL12-stimulated PI3K activity in EC requires Rac1-GTP co-regulation. Together, this data identify the role of FGD5 to generate Rac1-GTP to regulate pro-angiogenic CXCR4-dependent PI3K-β signaling in EC. Inhibition of FGD5 activity may complement current angiogenesis inhibitor drugs.

CD63-mediated cloaking of VEGF in small extracellular vesicles contributes to anti-VEGF therapy resistance

Despite wide use of anti-vascular endothelial growth factor (VEGF) therapy for many solid cancers, most individuals become resistant to this therapy, leading to disease progression. Therefore, new biomarkers and strategies for blocking adaptive resistance of cancer to anti-VEGF therapy are needed. As described here, we demonstrate that cancer-derived small extracellular vesicles package increasing quantities of VEGF and other factors in response to anti-VEGF therapy. The packaging process of VEGF into small extracellular vesicles (EVs) is mediated by the tetraspanin CD63. Furthermore, small EV-VEGF (eVEGF) is not accessible to anti-VEGF antibodies and can trigger intracrine VEGF signaling in endothelial cells. eVEGF promotes angiogenesis and enhances tumor growth despite bevacizumab treatment. These data demonstrate a mechanism where VEGF is partitioned into small EVs and promotes tumor angiogenesis and progression. These findings have clinical implications for biomarkers and therapeutic strategies for ovarian cancer.

In vivo efficacy of bevacizumab-loaded albumin nanoparticles in the treatment of colorectal cancer

Bevacizumab (as other monoclonal antibodies) has now become a mainstay in the treatment of several cancers in spite of some limitations, including poor tumour penetration and the development of resistance mechanisms. Its nanoencapsulation may be an adequate strategy to minimize these problems. The aim of this work was to evaluate the efficacy of bevacizumab-loaded nanoparticles (B-NP-PEG) on a xenograft model of human colorectal cancer. For this purpose, human serum albumin nanoparticles were prepared by coacervation, then coated with poly(ethylene glycol) and freeze-dried. B-NP-PEG displayed a mean size of about 300 nm and a bevacizumab loading of approximately 145 μg/mg. An in vivo study was conducted in the HT-29 xenograft model of colorectal cancer. Both, free and nanoencapsulated bevacizumab, induced a similar reduction in the tumour growth rate of about 50%, when compared to controls. By microPET imaging analysis, B-NP-PEG was found to be a more effective treatment in decreasing the glycolysis and metabolic tumour volume than free bevacizumab, suggesting higher efficacy. These results correlated well with the capability of B-NP-PEG to increase about fourfold the levels of intratumour bevacizumab, compared with the conventional formulation. In parallel, B-NP-PEG displayed six-times lower amounts of bevacizumab in blood than the aqueous formulation of the antibody, suggesting a lower incidence of potential undesirable side effects. In summary, albumin-based nanoparticles may be adequate carriers to promote the delivery of monoclonal antibodies (i.e. bevacizumab) to tumour tissues. Graphical abstract.

Joint IARC/NCI International Cancer Seminar Series Report: expert consensus on future directions for ovarian carcinoma research

Recently, ovarian cancer research has evolved considerably because of the emerging recognition that rather than a single disease, ovarian carcinomas comprise several different histotypes that vary by etiologic origin, risk factors, molecular profiles, therapeutic approaches and clinical outcome. Despite significant progress in our understanding of the etiologic heterogeneity of ovarian cancer, as well as important clinical advances, it remains the eighth most frequently diagnosed cancer in women worldwide and the most fatal gynecologic cancer. The International Agency for Research on Cancer and the United States National Cancer Institute jointly convened an expert panel on ovarian carcinoma to develop consensus research priorities based on evolving scientific discoveries. Expertise ranged from etiology, prevention, early detection, pathology, model systems, molecular characterization and treatment/clinical management. This report summarizes the current state of knowledge and highlights expert consensus on future directions to continue advancing etiologic, epidemiologic and prognostic research on ovarian carcinoma.

Therapy Resistance in Cancers: Phenotypic, Metabolic, Epigenetic and Tumour Microenvironmental Perspectives

BACKGROUND

Chemoresistance is a vital problem in cancer therapy where cancer cells develop mechanisms to encounter the effect of chemotherapeutics, resulting in cancer recurrence. In addition, chemotherapy- resistant leads to the formation of a more aggressive form of cancer cells, which, in turn, contributes to the poor survival of patients with cancer.

OBJECTIVE

In this review, we aimed to provide an overview of how the therapy resistance property evolves in cancer cells, contributing factors and their role in cancer chemoresistance, and exemplified the problems of some available therapies.

METHODS

The published literature on various electronic databases including, Pubmed, Scopus, Google scholar containing keywords cancer therapy resistance, phenotypic, metabolic and epigenetic factors, were vigorously searched, retrieved and analyzed.

RESULTS

Cancer cells have developed a range of cellular processes, including uncontrolled activation of Epithelial- Mesenchymal Transition (EMT), metabolic reprogramming and epigenetic alterations. These cellular processes play significant roles in the generation of therapy resistance. Furthermore, the microenvironment where cancer cells evolve effectively contributes to the process of chemoresistance. In tumour microenvironment immune cells, Mesenchymal Stem Cells (MSCs), endothelial cells and cancer-associated fibroblasts (CAFs) contribute to the maintenance of therapy-resistant phenotype via the secretion of factors that promote resistance to chemotherapy.

CONCLUSION

To conclude, as these factors hinder successful cancer therapies, therapeutic resistance property of cancer cells is a subject of intense research, which in turn could open a new horizon to aim for developing efficient therapies.

Alternative Vascularization Mechanisms in Tumor Resistance to Therapy

Simple Summary

Tumors rely on blood vessels to grow and metastasize. Malignant tumors can employ different strategies to create a functional vascular network. Tumor cells can use normal processes of vessel formation but can also employ cancer-specific mechanisms, by co-opting normal vessels present in tissues or by turning themselves into vascular cells. These different types of tumor vessels have specific molecular and functional characteristics that profoundly affect tumor behavior and response to therapies, including drugs targeting the tumor vasculature (antiangiogenic therapies). In this review, we discuss how vessels formed by different mechanisms affect the intrinsic sensitivity of tumors to therapy and, on the other hand, how therapies can affect tumor vessel formation, leading to resistance to drugs, cancer recurrence, and treatment failure. Potential strategies to avoid vessel-mediated resistance to antineoplastic therapies will be discussed.

Abstract

Blood vessels in tumors are formed through a variety of different mechanisms, each generating vessels with peculiar structural, molecular, and functional properties. This heterogeneity has a major impact on tumor response or resistance to antineoplastic therapies and is now emerging as a promising target for strategies to prevent drug resistance and improve the distribution and efficacy of antineoplastic treatments. This review presents evidence of how different mechanisms of tumor vessel formation (vasculogenesis, glomeruloid proliferation, intussusceptive angiogenesis, vasculogenic mimicry, and vessel co-option) affect tumor responses to antiangiogenic and antineoplastic therapies, but also how therapies can promote alternative mechanisms of vessel formation, contributing to tumor recurrence, malignant progression, and acquired drug resistance. We discuss the possibility of tailoring treatment strategies to overcome vasculature-mediated drug resistance or to improve drug distribution and efficacy.

Monotherapy and Combination Therapy Using Anti-Angiogenic Nanoagents to Fight Cancer

Anti-angiogenic therapy, targeting vascular endothelial cells (ECs) to prevent tumor growth, has been attracting increasing attention in recent years, beginning with bevacizumab (Avastin) through its Phase II/III clinical trials on solid tumors. However, these trials showed only modest clinical efficiency; moreover, anti-angiogenic therapy may induce acquired resistance to the drugs employed. Combining advanced drug delivery techniques (e.g., nanotechnology) or other therapeutic strategies (e.g., chemotherapy, radiotherapy, phototherapy, and immunotherapy) with anti-angiogenic therapy results in significantly synergistic effects and has opened a new horizon in fighting cancer. Herein, clinical difficulties in using traditional anti-angiogenic therapy are discussed. Then, several promising applications of anti-angiogenic nanoagents in monotherapies and combination therapies are highlighted. Finally, the challenges and perspectives of anti-angiogenic cancer therapy are summarized. A useful introduction to anti-angiogenic strategies, which may significantly improve therapeutic outcomes, is thus provided.

The Heterogeneity of Breast Cancer Metabolism

Despite advances in screening, therapy, and surveillance that have improved patient survival rates, breast cancer is still the most commonly diagnosed cancer and the second leading cause of cancer mortality among women [1]. Breast cancer is a highly heterogeneous disease rooted in a genetic basis, influenced by extrinsic stimuli, and reflected in clinical behavior. The diversity of breast cancer hormone receptor status and the expression of surface molecules have guided therapy decisions for decades; however, subtype-specific treatment often yields diverse responses due to varying tumor evolution and malignant potential. Although the mechanisms behind breast cancer heterogeneity is not well understood, available evidence suggests that studying breast cancer metabolism has the potential to provide valuable insights into the causes of these variations as well as viable targets for intervention.

Optimized Combination of HDACI and TKI Efficiently Inhibits Metabolic Activity in Renal Cell Carcinoma and Overcomes Sunitinib Resistance

Clear cell renal cell carcinoma (ccRCC) is characterized by high histone deacetylase (HDAC) activity triggering both cell motility and the development of metastasis. Therefore, there is an unmet need to establish innovative strategies to advance the use of HDAC inhibitors (HDACIs). We selected a set of tyrosine kinase inhibitors (TKIs) and HDACIs to test them in combination, using the validated therapeutically guided multidrug optimization (TGMO) technique based on experimental testing and in silico data modeling. We determined a synergistic low-dose three-drug combination decreasing the cell metabolic activity in metastatic ccRCC cells, Caki-1, by over 80%. This drug combination induced apoptosis and showed anti-angiogenic activity, both in original Caki-1 and in sunitinib-resistant Caki-1 cells. Through phosphoproteomic analysis, we revealed additional targets to improve the translation of this combination in 3-D (co-)culture systems. Cell-cell and cell-environment interactions increased, reverting the invasive and metastatic phenotype of Caki-1 cells. Our data suggest that our optimized low-dose drug combination is highly effective in complex in vitro settings and promotes the activity of HDACIs.

Reactive Oxygen Species Induce Endothelial Differentiation of Liver Cancer Stem-Like Sphere Cells through the Activation of Akt/IKK Signaling Pathway

Cancer stem cells (CSCs) from various cancers are able to transdifferentiate into endothelial cells and further form functional blood vessels, indicating another possible resistance mechanism to antiangiogenic agents. However, it remains unclear whether CSCs from hepatocellular carcinoma have the ability to differentiate into endothelial cells, and thus resulting in resistance to antiangiogenic therapy targeting VEGF. Reactive oxygen species (ROS) are involved in the self-renewal and differentiation of CSCs, yet, their role in endothelial differentiation of CSCs has been poorly understood. In this study, we found that cancer stem-like sphere cells enriched from human hepatocellular carcinoma cell line Hep G2 could differentiate into endothelial cells morphologically and functionally, and this process could be blocked by Akt1/2 kinase inhibitor and IKK-β inhibitor BAY 11-7082 but not by Bevacizumab, a VEGFA-binding antibody, and DAPT, a γ-secretase inhibitor. Both hydrogen peroxide and BSO (an inhibitor of GSH biosynthesis) induce the differentiation of cancer stem-like sphere cells into endothelial cells, which can be canceled by the antioxidant N-Acetyl-L-cysteine (NAC). We also found that hydrogen peroxide or BSO induces the phosphorylation of Akt and IKK of endothelial differentiated sphere cells. Accordingly, both Akt1/2 kinase inhibitor and BAY 11-7082 inhibited hydrogen peroxide and BSO-mediated endothelial differentiation of cancer stem-like sphere cells. Collectively, the results of the present study demonstrate that cancer stem-like sphere cells from Hep G2 are able to differentiate into endothelial cells both morphologically and functionally, and this process is independent of VEGF and NOTCH signaling but dependent on the activation of Akt and IKK. ROS promote endothelial differentiation of cancer stem-like sphere cells through activation of Akt/IKK signaling pathway. Therefore, our study reveals a novel mechanism of resistance to conventional antiangiogenic therapy and may provide a potential therapeutic target for liver cancer treatment.

Inactivation of endothelial cell phosphoinositide 3-kinase β inhibits tumor angiogenesis and tumor growth

Angiogenesis inhibitors, such as the receptor tyrosine kinase (RTK) inhibitor sunitinib, target vascular endothelial growth factor (VEGF) signaling in cancers. However, only a fraction of patients respond, and most ultimately develop resistance to current angiogenesis inhibitor therapies. Activity of alternative pro-angiogenic growth factors, acting via RTK or G-protein coupled receptors (GPCR), may mediate VEGF inhibitor resistance. The phosphoinositide 3-kinase (PI3K)β isoform is uniquely coupled to both RTK and GPCRs. We investigated the role of endothelial cell (EC) PI3Kβ in tumor angiogenesis. Pro-angiogenic GPCR ligands were expressed by patient-derived renal cell carcinomas (PD-RCC), and selective inactivation of PI3Kβ reduced PD-RCC-stimulated EC spheroid sprouting. EC-specific PI3Kβ knockout (ΕC-βKO) in mice potentiated the sunitinib-induced reduction in subcutaneous growth of LLC1 and B16F10, and lung metastasis of B16F10 tumors. Compared to single-agent sunitinib treatment, tumors in sunitinib-treated ΕC-βKO mice showed a marked decrease in microvessel density, and reduced new vessel formation. The fraction of perfused mature tumor microvessels was increased in ΕC-βKO mice suggesting immature microvessels were most sensitive to combined sunitinib and PI3Kβ inactivation. Taken together, EC PI3Kβ inactivation with sunitinib inhibition reduces microvessel turnover and decreases heterogeneity of the tumor microenvironment, hence PI3Kβ inhibition may be a useful adjuvant antiangiogenesis therapy with sunitinib.

Resistin: An inflammatory cytokine with multi-faceted roles in cancer

Systemic and organ-confined inflammation has been associated with cancer development and progression. Resistin, initially described as an adipocyte-derived cytokine in mice, is mostly expressed by the macrophages in humans. It has potent pro-inflammatory properties, and its elevated serum levels are detected in cancer patients. Aberrant expression of resistin receptors is also reported in several malignancies and associated with aggressive clinicopathological features. Several lines of evidence demonstrate that resistin, acting through its different receptors, promotes tumor growth, metastasis, and chemoresistance by influencing a variety of cellular phenotypes as well as by modulating the tumor microenvironment. Racially disparate expression of resistin has also attracted much interest, considering prevalent cancer health disparities. This review discusses the aberrant expression of resistin and its receptors, its diverse downstream signaling and impact on tumor growth, metastasis, angiogenesis, and therapy resistance to support its clinical exploitation in biomarker and therapeutic development.

Drug resistance in cancer: mechanisms and tackling strategies

Drug resistance developed towards conventional therapy is one of the important reasons for chemotherapy failure in cancer. The various underlying mechanism for drug resistance development in tumor includes tumor heterogeneity, some cellular levels changes, genetic factors, and others novel mechanisms which have been highlighted in the past few years. In the present scenario, researchers have to focus on these novel mechanisms and their tackling strategies. The small molecules, peptides, and nanotherapeutics have emerged to overcome the drug resistance in cancer. The drug delivery systems with targeting moiety enhance the site-specificity, receptor-mediated endocytosis, and increase the drug concentration inside the cells, thus minimizing drug resistance and improve their therapeutic efficacy. These therapeutic approaches work by modulating the different pathways responsible for drug resistance. This review focuses on the different mechanisms of drug resistance and the recent advancements in therapeutic approaches to improve the sensitivity and effectiveness of chemotherapeutics.

Roles of lncRNAs in cancer: Focusing on angiogenesis

Approximately 98% of the human genome consists of non-coding sequences that are classified into two classes by size: small non-coding RNAs (≤200 nucleotides) and long non-coding RNAs (≥200 nucleotides). Long non-coding RNAs (lncRNAs) are involved in various cellular events and act as guides, signals, decoys, and dynamic scaffolds. Due to their oncogenic and tumor suppressive roles, lncRNAs are important in cancer development and growth. LncRNAs play their roles by modulating cancer hallmarks, including DNA damage, metastasis, immune escape, cell stemness, drug resistance, metabolic reprogramming, and angiogenesis. Angiogenesis is vital for solid tumors which guarantees their growth beyond 2 mm³. Tumor angiogenesis is a complex process and is regulated through interaction between pro-angiogenic and anti-angiogenic factors within the tumor microenvironment. There are accumulating evidence that different lncRNAs regulate tumor angiogenesis. In this paper, we described the functions and mechanisms of lncRNAs in tumor angiogenesis.

Resistance Mechanisms to Anti-angiogenic Therapies in Cancer

Tumor growth and metastasis rely on tumor vascular network for the adequate supply of oxygen and nutrients. Tumor angiogenesis relies on a highly complex program of growth factor signaling, endothelial cell (EC) proliferation, extracellular matrix (ECM) remodeling, and stromal cell interactions. Numerous pro-angiogenic drivers have been identified, the most important of which is the vascular endothelial growth factor (VEGF). The importance of pro-angiogenic inducers in tumor growth, invasion and extravasation make them an excellent therapeutic target in several types of cancers. Hence, the number of anti-angiogenic agents developed for cancer treatment has risen over the past decade, with at least eighty drugs being investigated in preclinical studies and phase I-III clinical trials. To date, the most common approaches to the inhibition of the VEGF axis include the blockade of VEGF receptors (VEGFRs) or ligands by neutralizing antibodies, as well as the inhibition of receptor tyrosine kinase (RTK) enzymes. Despite promising preclinical results, anti-angiogenic monotherapies led only to mild clinical benefits. The minimal benefits could be secondary to primary or acquired resistance, through the activation of alternative mechanisms that sustain tumor vascularization and growth. Mechanisms of resistance are categorized into VEGF-dependent alterations, non-VEGF pathways and stromal cell interactions. Thus, complementary approaches such as the combination of these inhibitors with agents targeting alternative mechanisms of blood vessel formation are urgently needed. This review provides an updated overview on the pathophysiology of angiogenesis during tumor growth. It also sheds light on the different pro-angiogenic and anti-angiogenic agents that have been developed to date. Finally, it highlights the preclinical evidence for mechanisms of angiogenic resistance and suggests novel therapeutic approaches that might be exploited with the ultimate aim of overcoming resistance and improving clinical outcomes for patients with cancer.

The Role of Kinase Signaling in Resistance to Bevacizumab Therapy for Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is the most malignant primary brain tumor and is characterized by vascular hyperplasia, necrosis, and high cell proliferation. Despite current standard therapies, including surgical resection and chemoradiotherapy, GBM patients survive for only about 15 months after diagnosis. Recently, the U.S. Food and Drug Administration (FDA) has approved an antiangiogenesis medication for recurrent GBM-bevacizumab-which has improved progression-free survival in GBM patients. Although bevacizumab has resulted in significant early clinical benefit, it inescapably predisposes tumor to relapse that can be represented as an infiltrative phenotype. Fundamentally, bevacizumab antagonizes the vascular endothelial growth factor A (VEGF_A), which is consistently released on both endothelial cells (ECs) and GBM cells. Actually, VEGF_A inhibition on the ECs leads to the suppression of vascular progression, permeability, and the vasogenic edema. However, the consequence of the VEGF_A pathway blockage on the GBM cells remains controversial. Nevertheless, a piece of evidence supports the relationship between bevacizumab application and compensatory activation of kinase signaling within GBM cells, leading to a tumor cell invasion known as the main mechanism of bevacizumab-induced tumor resistance. A complete understanding of kinase responses associated with tumor invasion in bevacizumab-resistant GBMs offers new therapeutic opportunities. Thus, this study aimed at presenting a brief overview of preclinical and clinical data of the tumor invasion and resistance induced by bevacizumab administration in GBMs, with a focus on the kinase responses during treatment. The novel therapeutic strategies to overcome this resistance by targeting protein kinases have also been summarized.

Potential Therapeutic Strategies for Lung and Breast Cancers through Understanding the Anti-Angiogenesis Resistance Mechanisms

Breast and lung cancers are among the top cancer types in terms of incidence and mortality burden worldwide. One of the challenges in the treatment of breast and lung cancers is their resistance to administered drugs, as observed with angiogenesis inhibitors. Based on clinical and pre-clinical findings, these two types of cancers have gained the ability to resist angiogenesis inhibitors through several mechanisms that rely on cellular and extracellular factors. This resistance is mediated through angiogenesis-independent vascularization, and it is related to cancer cells and their microenvironment. The mechanisms that cancer cells utilize include metabolic symbiosis and invasion, and they also take advantage of neighboring cells like macrophages, endothelial cells, myeloid and adipose cells. Overcoming resistance is of great interest, and researchers are investigating possible strategies to enhance sensitivity towards angiogenesis inhibitors. These strategies involved targeting multiple players in angiogenesis, epigenetics, hypoxia, cellular metabolism and the immune system. This review aims to discuss the mechanisms of resistance to angiogenesis inhibitors and to highlight recently developed approaches to overcome this resistance.

Low-Dose Anti-Angiogenic Therapy Sensitizes Breast Cancer to PD-1 Blockade

PURPOSE

Despite its enormous successes, the overall response rate of cancer immunotherapy remains suboptimal, especially in breast cancer. There is an increased interest in combining immune checkpoint inhibitor with targeted agents to enhance antitumor effect. Anti-angiogenic drugs have been shown to synergize with immune checkpoint blockades, but the optimal setting for combining these two modalities and the underlying mechanisms of synergistic responses are not fully understood.

EXPERIMENTAL DESIGN

We tested the combination of anti-PD-1 and different doses of VEGFR2-targeting agents in syngeneic breast cancer mouse models. Tumor-infiltrated immune cell subsets were profiled by flow cytometry. A cytokine array was carried out to identify inflammatory changes in different treatment conditions. The efficacy of combined anti-angiogenic and anti-PD-1 therapy was further evaluated in patients with advanced triple-negative breast cancer (TNBC).

RESULTS

Blockade of VEGFR2 sensitizes breast tumors to PD-1 blockade in a dose-dependent manner. Although both conventional and low-dose anti-VEGFR2 antibody treatments normalize tumor vessels, low-dose VEGFR2 blockade results in more robust immune cell infiltration and activation and promotes the secretion of osteopontin (OPN) by CD8⁺ T cells. OPN subsequently induces tumor cell production of TGF-β, which in turn upregulates PD-1 expression on immune cells. In patients with advanced TNBC, combined treatment with low-dose anti-VEGFR2 inhibitor and anti-PD-1 demonstrated excellent tolerability and efficacy. Higher OPN and TGF-β expressions correlated with improved treatment responses.

CONCLUSIONS

Together, these results demonstrate a dose-dependent synergism between anti-angiogenic therapy and immune checkpoint blockade, thus providing important insights into the optimal strategies for combining immunotherapy with molecular-targeted agents.

Rolipram optimizes therapeutic effect of bevacizumab by enhancing proapoptotic, antiproliferative signals in a glioblastoma heterotopic model

The unstable response to bevacizumab is a big dilemma in the antiangiogenic therapy of high-grade glioma that appears to be linked to an increase in the post-treatment intratumor levels of hypoxia-inducible factor 1 α (HIF1α) and active AKT. Particularly, a selective phosphodiesterase IV (PDE4) inhibitor, rolipram is capable of inhibiting HIF1α and AKT in cancer cells. Here, the effect of bevacizumab alone and in presence of rolipram on therapeutic efficacy, intratumor hypoxia levels, angiogenesis, apoptosis and proliferation mechanisms were evaluated. BALB/c mice bearing C6 glioma were received bevacizumab and rolipram either alone or combined for 30 days (n = 11/group). At the last day of treatments, apoptosis, proliferation and microvessel density, in xenografts (3/group) were detected by TUNEL staining, Ki67 and CD31 markers, respectively. Relative expression of target proteins was measured using western blotting. Bevacizumab initially hindered the tumor progression but its antitumor effect was weakened later despite the vascular regression and apoptosis induction. Unpredictably, bevacizumab-treated tumors exhibited the highest cell proliferation coupled with PDE4A, HIF1α and AKT upregulation and p53 downregulation and reversed by co-treatment with rolipram. Unlike a similar antivascular pattern to bevacizumab, rolipram consistently led to a more tumor growth suppression and proapoptotic effect versus bevacizumab. Co-treatment maximally hampered the tumor progression and elongated survival along with the major vascular regression, hypoxia, apoptosis induction, p53 and caspase activities. In conclusion, superior and persistent therapeutic efficacy of co-treatment provides a new insight into antiangiogenic therapy of malignant gliomas, suggesting to be a potential substitute in selected patients.

Mechanisms of resistance to anti-angiogenic treatments

Hailed as the cancer treatment to end all the resistance to treatment, anti-angiogenic therapy turned out to be not quite what was promised. The hope that this therapeutic approach would not have suffered by the phenomenon of resistance was based on the fact that was targeting normal vessels rather than tumour cells prone to mutation and subject to drug induced selection. However, reality turned out to be more complex and since 1997, several mechanisms of resistance have been described to the point that the study of resistance to these drugs is now a very large field. Far from being exhaustive, this paper presents the main mechanisms discovered trough some examples.

Enhanced efficacy of sitravatinib in metastatic models of antiangiogenic therapy resistance

Tyrosine kinase inhibitors (TKIs) that primarily target angiogenesis are approved to treat several cancers in the metastatic setting; however, resistance is common. Sequential treatment or 'switching' from one TKI to another following failure can be effective, but predicting which drugs will have cross-over sensitivity remains a challenge. Here we examined sitravatinib (MGCD516), a spectrum-selective TKI able to block MET, TAM (TYRO3, AXL, MerTK) and multiple receptor families (including PDGFRs, VEGFRs, and Ephs). Transcriptomic analysis of several mouse and human cell lines revealed diverse molecular changes after resistance to two TKIs (sunitinib and axitinib) with multiple sitravatinib targets found to be upregulated. Sitravatinib treatment in vitro resulted in enhanced anti-proliferative effects in resistant cells and was improved compared to TKIs with similar target profiles. In vivo, primary tumor growth inhibition after sitravatinib treatment in mice was enhanced in resistant tumors and metastasis suppression improved when tumors were surgically removed. Together, these results suggest that the diverse and often inconsistent compensatory signaling mechanisms found to contribute to TKI resistance may paradoxically improve the tumor-inhibiting effects of broad-spectrum TKIs such as sitravatinib that are able to block multiple signaling pathways. Sitravatinib in the second-line setting following antiangiogenic TKI treatment may have enhanced inhibitory effects in local and disseminated disease, and improve outcomes in patients with refractory disease.

Exogenous sickle erythrocytes combined with vascular disruption trigger disseminated tumor vaso-occlusion and lung tumor regression

Hypoxic tumor niches are chief causes of treatment resistance and tumor recurrence. Sickle erythrocytes' (SSRBCs') intrinsic oxygen-sensing functionality empowers them to access such hypoxic niches wherein they form microaggregates that induce focal vessel closure. In search of measures to augment the scale of SSRBC-mediated tumor vaso-occlusion, we turned to the vascular disrupting agent, combretastatin A-4 (CA-4). CA-4 induces selective tumor endothelial injury, blood stasis, and hypoxia but fails to eliminate peripheral tumor foci. In this article, we show that introducing deoxygenated SSRBCs into tumor microvessels treated with CA-4 and sublethal radiation (SR) produces a massive surge of tumor vaso-occlusion and broadly propagated tumor infarctions that engulfs treatment-resistant hypoxic niches and eradicates established lung tumors. Tumor regression was histologically corroborated by significant treatment effect. Treated tumors displayed disseminated microvessels occluded by tightly packed SSRBCs along with widely distributed pimidazole-positive hypoxic tumor cells. Humanized HbS-knockin mice (SSKI) but not HbA-knockin mice (AAKI) showed a similar treatment response underscoring SSRBCs as the paramount tumoricidal effectors. Thus, CA-4-SR-remodeled tumor vessels license SSRBCs to produce an unprecedented surge of tumor vaso-occlusion and infarction that envelops treatment-resistant tumor niches resulting in complete tumor regression. Strategically deployed, these innovative tools constitute a major conceptual advance with compelling translational potential.

Phase II trial of nintedanib in patients with bevacizumab-resistant recurrent epithelial ovarian, tubal, and peritoneal cancer

BACKGROUND

Bevacizumab provides benefit in epithelial ovarian cancer (EOC), yet resistance to bevacizumab often occurs. We determined if nintedanib, a tyrosine kinase inhibitor of VEGF, FGF, and PDGF receptors has antitumor activity in bevacizumab-resistant recurrent EOC, tubal, and peritoneal cancer.

METHODS

This phase II study evaluated nintedanib 200 mg/day until disease progression or unacceptable toxicity. The primary objective was 6-month progression free survival (PFS6m). Secondary objectives were response rate and toxicity. Simon two-stage optimal design was used. Baseline angiogenic plasma biomarkers were measured.

RESULTS

27 patients were enrolled evaluable for PFS; 26 were evaluable for PFS6m. The median age was 65 years (range 44-73); 89.9% had high-grade serous EOC; 70% received at least >2 prior chemotherapies; and 81% (22/27) had chemoresistant disease. With median follow up of 15.6 months (range 2-38) the PFS6m rate was 11.5% (3/26). Three participants had long duration of disease control (8-16 months). Median PFS and overall survival were 1.8 and 16 months, respectively. Response rate was 7.4% (2/27 PR). Thirty-seven percent (10/27) had stable disease, while 56% (15/27) had progressive disease. Adverse events included Grade 3 liver enzyme elevation (15%), Grade 3 diarrhea (7%), Grade 2 fatigue (7%), and Grade 2 nausea/vomiting (15%). PD patients exhibited higher levels of CD73, IL6, and VEGFD (p < 0.05) compared to PR/SD patients. IL6 was associated with worse PFS (p = 0.03).

CONCLUSIONS

Single-agent nintedanib has minimal activity in an unselected bevacizumab-resistant EOC population. Nintedanib was tolerable and toxicities were manageable. Plasma CD73, IL6, and VEGFD were identified as prognostic markers for progressive disease, and IL6 was associated with worse PFS confirming similar observations made in patients treated with other anti-angiogenic agents.

Hypoxia, angiogenesis, and metabolism in the hereditary kidney cancers

The field of hereditary kidney cancer has begun to mature following the identification of several germline syndromes that define genetic and molecular features of this cancer. Molecular defects within these hereditary syndromes demonstrate consistent deficits in angiogenesis and metabolic signaling, largely driven by altered hypoxia signaling. The classical mutation, loss of function of the von Hippel-Lindau (VHL) tumor suppressor, provides a human pathogenesis model for critical aspects of pseudohypoxia. These features are mimicked in a less common hereditary renal tumor syndrome, known as hereditary leiomyomatosis and renal cell carcinoma. Here, we review renal tumor angiogenesis and metabolism from a HIF-centric perspective, considering alterations in the hypoxic landscape, and molecular deviations resulting from high levels of HIF family members. Mutations underlying HIF deregulation drive multifactorial aberrations in angiogenic signals and metabolism. The mechanisms by which these defects drive tumor growth are still emerging. However, the distinctive patterns of angiogenesis and glycolysis-/glutamine-dependent bioenergetics provide insight into the cellular environment of these cancers. The result is a scenario permissive for aggressive tumorigenesis especially within the proximal renal tubule. These features of tumorigenesis have been highly actionable in kidney cancer treatments, and will likely continue as central tenets of kidney cancer therapeutics.

Résistance aux inhibiteurs des tyrosines kinases dans le cancer du rein

FOCUS ON RESISTANCE TO TYROSINE KINASE INHIBITORS IN RENAL CANCER: The last decade has seen significant advances in understanding the biology and genetics of kidney cancer, some of which have radically changed treatment standards, including the emergence of targeted therapies. TKIs have significantly improved outcome in patients with metastatic disease. Nevertheless, a subset of patients (approximately 25 %) does not show any clinical benefit from targeted therapies. In many cases, patients initially respond to therapy but resistance to targeted agents has been shown to develop after a median of 6-12 months of treatment. Two general models of tumor resistance to anti-angiogenic agents targeting the VEGF pathway have been proposed: an adaptive (evasive) resistance, which occurs after a prolonged application of a drug (providing a period of tumor control), or intrinsic one (preexisting) non-responsiveness despite the presence of an active agent, showing no therapeutic benefit. Intrinsic resistance is related to tumor redundancy of pro-angiogenic pathways. Acquired resistance is associated with activation of alternative pathways either by upregulation of the VEGF pathway or by recruitment of alternative angiogenic factors responsible for tumor revascularization. Because different combinations and sequences of TKI are tested in clinical trials and immunotherapy (alone or in combination) radically alters patient management in its metastatic disease, the current effort aims at identifying resistance processes, evaluating their importance and proposing rational therapeutic approaches in order to obtain an additional clinical benefit. Our article summarizes the different mechanisms of resistance described in the literature.

Ovarian cancer cell-derived lysophosphatidic acid induces glycolytic shift and cancer-associated fibroblast-phenotype in normal and peritumoral fibroblasts

Cancer-associated fibroblasts (CAFs) play a critical role in cancer progression, metastasis, and therapy resistance. Molecular events that confer CAF-phenotype to predecessor-cells are not fully understood. We demonstrate here that the ovarian cancer cell-conditioned medium (OCC-CM) induces CAF-phenotype in MRC5 lung-fibroblasts and it can be mimicked by LPA. While OCC-CM and LPA stimulated the expression of cellular CAF-markers by 3-days, they induced aerobic glycolysis, a metabolic marker for CAF, by 6 hrs. OCC-CM/LPA-induced glycolysis in lung (MRC5) as well as ovarian fibroblasts (NOF151) was inhibited by the LPA-receptor antagonist, Ki16425. Ovarian cancer patient-derived ascitic fluid-induced aerobic glycolysis in both NFs and Ovarian CAFs and it was inhibited by Ki16425. Further analysis indicated that LPA upregulated HIF1α-levels and the silencing of HIF1α attenuated LPA-induced glycolysis in both NOFs and CAFs. These results establish LPA-induced glycolytic-shift as the earliest, potentially priming event, in NF to CAF-transition. These findings also identify a role for LPA-LPAR-HIF1α signaling-hub in the maintenance of the glycolytic-phenotype in CAFs. Our results provide evidence that targeted inhibition of LPA-mediated metabolic reprogramming in CAFs may represent an adjuvant therapy in ovarian cancer.

Metformin sensitizes hypoxia-induced gefitinib treatment resistance of HNSCC via cell cycle regulation and EMT reversal

Objectives

The objectives of this study were to explore the mechanisms of metformin sensitization to hypoxia-induced gefitinib treatment in resistant head and neck squamous cell carcinoma (HNSCC) and evaluate the effects of this combined treatment strategy.

Methods

The effects of gefitinib treatment on HNSCC were measured under normoxic and hypoxic conditions. The relationship between hypoxia and cell cycle and epithelial-mesenchymal transition (EMT) in tumor cells were analyzed. Palbociclib and LY294002 were used in combination with gefitinib to evaluate the effects on HNSCC cell cytotoxicity during hypoxia. Finally, metformin was used to evaluate the sensitizing effects of gefitinib treatment on HNSCC in vivo and in vitro.

Results

Cell viability and apoptosis assays demonstrated a significant difference in HNSCC cells treated with gefitinib between the normoxia and hypoxia groups. Hypoxia induced the expression of cyclin D1, decreased the percentage of cells in G1, and promoted the EMT of tumor cells. Both palbociclib and LY294002 enhanced gefitinib-induced cytotoxicity of HNSCC cells under hypoxic conditions. Encouragingly, metformin sensitized HNSCC to gefitinib treatment in vivo and in vitro.

Conclusion

Hypoxia promotes G1-S cell cycle progression and EMT in HNSCC, resulting in gefitinib treatment resistance. Metformin sensitizes HNSCC to gefitinib treatment, which might serve as a novel combined treatment strategy.

Selective delivery of PLXDC1 small interfering RNA to endothelial cells for anti-angiogenesis tumor therapy using CD44-targeted chitosan nanoparticles for epithelial ovarian cancer

Angiogenesis plays an essential role in the growth and metastasis of tumor cells, and the modulation of angiogenesis can be an effective approach for cancer therapy. We focused on silencing the angiogenic gene PLXDC1 as an important factor for anti-angiogenesis tumor therapy. Herein, we developed PLXDC1 small interfering siRNA (siRNA)-incorporated chitosan nanoparticle (CH-NP/siRNA) coated with hyaluronic acid (HA) to target the CD44 receptor on tumor endothelial cells. This study aimed to improve targeted delivery and enhance therapeutic efficacy for tumor anti-angiogenesis. The HA-CH-NP/siRNA was 200 ± 10 nm in size with a zeta potential of 26.4 mV. The loading efficiency of siRNA to the HA-CH-NP/siRNA was up to 60%. The selective binding of HA-CH-NP/siRNA to CD44-positive tumor endothelial cells increased by 2.1-fold compared with that of the CD44 nontargeted CH-NP/siRNA. PLXDC1 silencing by the HA-CH-NP/siRNA significantly inhibited tumor growth in A2780 tumor-bearing mice compared with that in the control group (p < .01), and mRNA expression of PLXDC1 was significantly reduced in the HA-CH-NP/siRNA-treated group. Furthermore, treatment with HA-CH-NP/siRNA resulted in significant inhibition of cell proliferation (p < .001), reduced microvessel density (p < .001), and increased cell apoptosis (p < .001). This study demonstrates that HA-CH-NP/siRNA is a highly selective delivery platform for siRNA, and has broad potential to be used in anti-angiogenesis tumor therapy.