Targeting vascular normalization: a promising strategy to improve immune-vascular crosstalk in cancer immunotherapy

Nanotherapeutic Formulations for the Delivery of Cancer Antiangiogenics

Antiangiogenic medications for cancer treatment have generally failed in showing substantial benefits in terms of prolonging life on their own; their effects are noticeable only when combined with chemotherapy. Moreover, treatments based on prolonged antiangiogenics administration have demonstrated to be ineffective in stopping tumor progression. In this scenario, nanotherapeutics can address certain issues linked to existing antiangiogenic treatments. More specifically, they can provide the ability to target the tumor's blood vessels to enhance drug accumulation and manage release, ultimately decreasing undesired side effects. Additionally, they enable the administration of multiple angiogenesis inhibitors at the same time as chemotherapy. Key reports in this field include the design of polymeric nanoparticles, inorganic nanoparticles, vesicles, and hydrogels for loading antiangiogenic substances like endostatin and interleukin-12. Furthermore, nanoformulations have been proposed to efficiently control relevant pro-angiogenic pathways such as VEGF, Tie2/Angiopoietin-1, HIF-1α/HIF-2α, and TGF-β, providing powerful approaches to block tumor growth and metastasis. In this article, we outline a selection of nanoformulations for antiangiogenic treatments for cancer that have been developed in the past ten years.

The inhibition of endothelial DLL4-NOTCH1 signaling by 2'-hydroxyflavanone enhances anti-PD-1 therapy in melanoma

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapeutics; however limited patient responses necessitate combination strategies to improve therapeutic efficacy. Among potential combination partners, drugs targeting DLL4-NOTCH1 signaling pathway-a critical regulator of vascular function-show promise as angiogenesis modulators, but their clinical development have been hindered by safety concerns. To address this challenge, we adopted a novel approach by screening natural compounds with a long history of human consumption. Building upon our earlier findings, we identified three inhibitors of DLL4-NOTCH1 signaling: steppogenin, sanggenon F, and dehydrovomifoliol. Steppogenin inhibited both DLL4 and NOTCH1 activities, while sanggenon F and dehydrovomifoliol selectively suppressed DLL4 and NOTCH1 activity, respectively. We assessed their impact on key angiogenic processes, including endothelial cell migration, sprouting, and proliferation, and elucidated the relative contributions of selective DLL4 or NOTCH1 inhibition to the anti-angiogenic effect. By comparing structurally similar compounds, we identified the 2'-hydroxyflavanone moiety as a key element for DLL4 inhibition. Notably, combining steppogenin with an ICI demonstrated that a nature-derived angiogenesis inhibitor can boost the anti-cancer effect of ICI in a mouse melanoma allograft model. This comprehensive analysis of structure-activity relationships and in vivo therapeutic evaluation provides valuable insights into the development of novel anti-angiogenic compounds for combination therapy with ICIs in cancer treatment.

Lipid Nanoparticle Delivery System for Normalization of Tumor Microenvironment and Tumor Vascular Structure

Tumors grow by receiving oxygen and nutrients from the surrounding blood vessels, leading to rapid angiogenesis. This results in functionally and structurally abnormal vasculature characterized by high permeability and irregular blood flow, causing hypoxia within the tumor microenvironment (TME). Hypoxia exacerbates the secretion of pro-angiogenic factors such as vascular endothelial growth factor (VEGF), further perpetuating abnormal vessel formation. This environment compromises the efficacy of radiotherapy, immunotherapy, and chemotherapy. In this study, we developed a pH-sensitive liposome (PSL) system, termed OD_PSL@AKB, to co-deliver oxygen (OD) and razuprotafib (AKB-9778) to tumors. This system rapidly responds to the acidic TME to alleviate hypoxia and inhibit VEGF secretion, restoring VE-cadherin expression in hypoxic endothelial cell/cancer cell cocultures. Our findings highlight the potential of OD_PSL@AKB in normalizing tumor vasculature and improving therapeutic efficacy.

Normalization of tumor vasculature by imiquimod: proposal for a new anticancer therapeutic indication for a TLR7 agonist

Imiquimod (IMQ), a drug from aminoquinoline group, is the toll-like receptor 7 (TLR7) agonist. It acts as an immunostimulant and radio-sensitizing agent. IMQ stimulates both innate and adaptive immune response. Despite studies conducted, there are no unambiguous data showing how IMQ affects the condition of tumor blood vessels. Tumor vasculature plays the main role in tumor progression. Formation of abnormal blood vessels increases area of hypoxia which recruits suppressor cells, blocks tumor infiltration by CD8+ T lymphocytes, inhibits efficacy of chemoterapeutic drug and leads to cancer relapse. Normalization is a type of therapy targeted at abnormal tumor blood vessels. Here, we demonstrated that 50 µg of IMQ inhibits the growth of melanoma tumors more efficiently, compared to other tested doses and the control group. Dose escalation did not improve the therapeutic antitumor potential of TLR7 agonist. A dose of 50 µg of IMQ most effectively reduced tumor blood vessel density. Imiquimod normalized tumor vasculature both structurally (by reducing vessel tortuosity and increasing pericyte coverage) and functionally (by improving tumor perfusion) in a dose-dependent manner. Hypoxia regions in tumors of treated mice were significantly reduced after IMQ administration. A dose of 50 µg of IMQ had also the greatest impact on the changes in tumor-infiltrating T lymphocytes levels. TLR7 agonist inhibited angiogenesis in treated mice. Functional vascular normalization by IMQ increases the effectiveness of low dose of doxorubicin. Higher dose of IMQ showed worse effects than lower doses including decreased tumor perfusion, increased tumor hypoxia and immunosuppression. This knowledge may help to optimize the combination of the selected IMQ dose with e.g. chemotherapy or radiotherapy to elicit synergistic effect in cancer treatment. To conclude, we outline IMQ repurposing as a vascular normalizing agent. Our research results may contribute to expanding the therapeutic indications for the use of IMQ in anticancer therapy in the future.

Harnessing the tumor microenvironment: targeted cancer therapies through modulation of epithelial-mesenchymal transition

The tumor microenvironment (TME) is integral to cancer progression, impacting metastasis and treatment response. It consists of diverse cell types, extracellular matrix components, and signaling molecules that interact to promote tumor growth and therapeutic resistance. Elucidating the intricate interactions between cancer cells and the TME is crucial in understanding cancer progression and therapeutic challenges. A critical process induced by TME signaling is the epithelial-mesenchymal transition (EMT), wherein epithelial cells acquire mesenchymal traits, which enhance their motility and invasiveness and promote metastasis and cancer progression. By targeting various components of the TME, novel investigational strategies aim to disrupt the TME's contribution to the EMT, thereby improving treatment efficacy, addressing therapeutic resistance, and offering a nuanced approach to cancer therapy. This review scrutinizes the key players in the TME and the TME's contribution to the EMT, emphasizing avenues to therapeutically disrupt the interactions between the various TME components. Moreover, the article discusses the TME's implications for resistance mechanisms and highlights the current therapeutic strategies toward TME modulation along with potential caveats.

The influence of endothelial metabolic reprogramming on the tumor microenvironment

Endothelial cells (ECs) that line blood vessels act as gatekeepers and shape the metabolic environment of every organ system. In normal conditions, endothelial cells are relatively quiescent with organ-specific expression signatures and metabolic profiles. In cancer, ECs are metabolically reprogrammed to promote the formation of new blood vessels to fuel tumor growth and metastasis. In addition to EC's role on tumor cells, the tortuous tumor vasculature contributes to an immunosuppressive environment by limiting T lymphocyte infiltration and activity while also promoting the recruitment of other accessory pro-angiogenic immune cells. These elements aid in the metastatic spreading of cancer cells and contribute to therapeutic resistance. The concept of restoring a more stabilized vasculature in concert with cancer immunotherapy is emerging as a potential approach to overcoming barriers in cancer treatment. This review summarizes the metabolism of endothelial cells, their regulation of nutrient uptake and delivery, and their impact in shaping the tumor microenvironment and anti-tumor immunity. We highlight new therapeutic approaches that target the tumor vasculature and harness the immune response. Appreciating the integration of metabolic state and nutrient levels and the crosstalk among immune cells, tumor cells, and ECs in the TME may provide new avenues for therapeutic intervention.

Subverting Attachment to Prevent Attacking: Alteration of Effector Immune Cell Migration and Adhesion as a Key Mechanism of Tumor Immune Evasion

Cell adhesion regulates specific migratory patterns, location, communication with other cells, physical interactions with the extracellular matrix, and the establishment of effector programs. Proper immune control of cancer strongly depends on all these events occurring in a highly accurate spatiotemporal sequence. In response to cancer-associated inflammatory signals, effector immune cells navigating the bloodstream shift from their patrolling exploratory migration mode to establish adhesive interactions with vascular endothelial cells. This interaction enables them to extravasate through the blood vessel walls and access the cancer site. Further adhesive interactions within the tumor microenvironment (TME) are crucial for coordinating their distribution in situ and for mounting an effective anti-tumor immune response. In this review, we examine how alterations of adhesion cues in the tumor context favor tumor escape by affecting effector immune cell infiltration and trafficking within the TME. We discuss the mechanisms by which tumors directly modulate immune cell adhesion and migration patterns to affect anti-tumor immunity and favor tumor evasion. We also explore indirect immune escape mechanisms that involve modifications of TME characteristics, such as vascularization, immunogenicity, and structural topography. Finally, we highlight the significance of these aspects in designing more effective drug treatments and cellular immunotherapies.

Towards Targeting Endothelial Rap1B to Overcome Vascular Immunosuppression in Cancer

The vascular endothelium, a specialized monolayer of endothelial cells (ECs), is crucial for maintaining vascular homeostasis by controlling the passage of substances and cells. In the tumor microenvironment, Vascular Endothelial Growth Factor A (VEGF-A) drives tumor angiogenesis, leading to endothelial anergy and vascular immunosuppression-a state where ECs resist cytotoxic CD8+ T cell infiltration, hindering immune surveillance. Immunotherapies have shown clinical promise. However, their effectiveness is significantly reduced by tumor EC anergy. Anti-angiogenic treatments aim to normalize tumor vessels and improve immune cell infiltration. Despite their potential, these therapies often cause significant systemic toxicities, necessitating new treatments. The small GTPase Rap1B emerges as a critical regulator of Vascular Endothelial Growth Factor Receptor 2 (VEGFR2) signaling in ECs. Our studies using EC-specific Rap1B knockout mice show that the absence of Rap1B impairs tumor growth, alters vessel morphology, and increases CD8+ T cell infiltration and activation. This indicates that Rap1B mediates VEGF-A's immunosuppressive effects, making it a promising target for overcoming vascular immunosuppression in cancer. Rap1B shares structural and functional similarities with RAS oncogenes. We propose that targeting Rap1B could enhance therapies' efficacy while minimizing adverse effects by reversing endothelial anergy. We briefly discuss strategies successfully developed for targeting RAS as a model for developing anti-Rap1 therapies.

Integrating electromagnetic cancer stress with immunotherapy: a therapeutic paradigm

An array of published cell-based and small animal studies have demonstrated a variety of exposures of cancer cells or experimental carcinomas to electromagnetic (EM) wave platforms that are non-ionizing and non-thermal. Overall effects appear to be inhibitory, inducing cancer cell stress or death as well as inhibition in tumor growth in experimental models. A variety of physical input variables, including discrete frequencies, amplitudes, and exposure times, have been tested, but drawing methodologic rationale and mechanistic conclusions across studies is challenging. Nevertheless, outputs such as tumor cytotoxicity, apoptosis, tumor membrane electroporation and leak, and reactive oxygen species generation are intriguing. Early EM platforms in humans employ pulsed electric fields applied either externally or using interventional tumor contact to induce tumor cell electroporation with stromal, vascular, and immunologic sparing. It is also possible that direct or external exposures to non-thermal EM waves or pulsed magnetic fields may generate electromotive forces to engage with unique tumor cell properties, including tumor glycocalyx to induce carcinoma membrane disruption and stress, providing novel avenues to augment tumor antigen release, cross-presentation by tumor-resident immune cells, and anti-tumor immunity. Integration with existing checkpoint inhibitor strategies to boost immunotherapeutic effects in carcinomas may also emerge as a broadly effective strategy, but little has been considered or tested in this area. Unlike the use of chemo/radiation and/or targeted therapies in cancer, EM platforms may allow for the survival of tumor-associated immunologic cells, including naïve and sensitized anti-tumor T cells. Moreover, EM-induced cancer cell stress and apoptosis may potentiate endogenous tumor antigen-specific anti-tumor immunity. Clinical studies examining a few of these combined EM-platform approaches are in their infancy, and a greater thrust in research (including basic, clinical, and translational work) in understanding how EM platforms may integrate with immunotherapy will be critical in driving advances in cancer outcomes under this promising combination.

Pericytes: jack-of-all-trades in cancer-related inflammation

Pericytes, recognized as mural cells, have long been described as components involved in blood vessel formation, playing a mere supporting role for endothelial cells (ECs). Emerging evidence strongly suggests their multifaceted roles in tissues and organs. Indeed, pericytes exhibit a remarkable ability to anticipate endothelial cell behavior and adapt their functions based on the specific cells they interact with. Pericytes can be activated by pro-inflammatory stimuli and crosstalk with immune cells, actively participating in their transmigration into blood vessels. Moreover, they can influence the immune response, often sustaining an immunosuppressive phenotype in most of the cancer types studied. In this review, we concentrate on the intricate crosstalk between pericytes and immune cells in cancer, highlighting the primary evidence regarding pericyte involvement in primary tumor mass dynamics, their contributions to tumor reprogramming for invasion and migration of malignant cells, and their role in the formation of pre-metastatic niches. Finally, we explored recent and emerging pharmacological approaches aimed at vascular normalization, including novel strategies to enhance the efficacy of immunotherapy through combined use with anti-angiogenic drugs.

The Past and Future of Angiogenesis as a Target for Cancer Therapy and Prevention

Cancer growth is dependent on angiogenesis, the formation of new blood vessels, which represents a hallmark of cancer. After this concept was established in the 1970s, inhibition of tumor development and metastases by blocking the neoangiogenic process has been an important approach to the treatment of tumors. However, antiangiogenic therapies are often administered when cancer has already progressed. The key to reducing the cancer burden is prevention. We noticed 20 years ago that a series of possible cancer chemopreventive agents showed antiangiogenic properties when tested in experimental models. This article reviews the relevant advances in the understanding of the rationale for targeting angiogenesis for cancer therapy, prevention, and interception and recently investigated substances with antiangiogenic activity that may be suitable for such strategies. Many compounds, either dietary derivatives or repurposed drugs, with antiangiogenic activity are possible tools for cancer angioprevention. Such molecules have a favorable safety profile and are likely to allow the prolonged duration necessary for an efficient preventive strategy. Recent evidence on mechanisms and possible use is described here for food derivatives, including flavonoids, retinoids, triterpenoids, omega fatty acids, and carotenoids from marine microorganisms. As examples, a number of compounds, including epigallocatechin, resveratrol, xanthohumol, hydroxytyrosol, curcumin, fenretinide, lycopene, fucoxanthin, and repurposed drugs, such as aspirin, β blockers, renin-angiotensin-aldosterone inhibitors, carnitines, and biguanides, are reviewed.

Evaluation of the efficacy of transarterial chemoembolization combined with microwave ablation followed by adjuvant therapy in patients with hepatocellular carcinoma

Objective

This study aimed to explore the efficacy of transarterial chemoembolization (TACE) combined with microwave ablation (MWA) adjuvant to lenvatinib and anti-PD-1 antibodies for patients with hepatocellular carcinoma (HCC).

Methods

A retrospective analysis of 67 patients with HCC treated at our hospital between October 2018 and May 2022 was conducted. All patients underwent a combination of TACE and MWA. Among them, 29 received postoperative treatment with molecular-targeted agents, like lenvatinib, along with anti-PD-1 antibodies such as sindilizumab, karelizumab, or tirilizumab. The remaining 38 patients did not receive postoperative systemic therapies, like targeted or immunotherapy. The survival and prognosis of all patients were analyzed.

Results

Nine patients in the observation group and 29 patients in the control group experienced recurrence, and the median progression-free survival 1 (PFS1) was not reached 'Not Applicable'(NA) and 17.05 months (P=0.035), respectively. Failure to combine adjuvant therapy was identified as an independent risk factor for tumor recurrence, and the observation group had a 0.245 times lower risk of recurrence compared to that in the control group (P=0.005). Multivariable Cox regression analysis confirmed that the maximum tumor size, and tumor number were risk factors for tumor recurrence. Patients with a large maximum tumor size had a 1.519 times higher risk of recurrence compared to those with a small maximum tumor size (P=0.006), and patients with a large number of tumors had a 5.978 times higher risk of recurrence compared to those with a small number of tumors (P=0.02). The median PFS2 of the two groups was 11.795 and 21.257 months, respectively, though not statistically significant (P=0.955). However, there was a disparity in the percentage of BCLC stages associated with recurrence between the two groups. In the observation group approximately 22.22% of patients progressed to stage C, while in the control group, this proportion was 34.48%. The observation group exhibited a lower risk of distant metastasis compared to the control group.

Conclusion

Adjuvant treatment of HCC following TACE combined with MWA improved PFS and achieved better clinical outcomes compared to that with TACE combined with MWA alone.