Tumor vasculature and microenvironment normalization: a possible mechanism of antiangiogenesis therapy

Advances in Trop-2 targeted antibody-drug conjugates for breast cancer: mechanisms, clinical applications, and future directions

Breast cancer remains a leading cause of cancer-related deaths among women worldwide, highlighting the need for novel therapeutic strategies. Trophoblast cell surface antigen 2 (Trop-2), a type I transmembrane glycoprotein highly expressed in various solid tumors including all subtypes of breast cancer, has emerged as a promising target for cancer therapy. This review focuses on recent advancements in Trop-2-targeted antibody-drug conjugates (ADCs) for breast cancer treatment. We comprehensively analyzed the structure and mechanism of action of ADCs, as well as the role of Trop-2 in breast cancer progression and prognosis. Several Trop-2-targeted ADCs, such as Sacituzumab Govitecan (SG) and Datopotamab Deruxtecan (Dato-DXd), have demonstrated significant antitumor activity in clinical trials for both triple-negative breast cancer (TNBC) and hormone receptor-positive/HER2-negative (HR+/HER2-) breast cancer. We systematically reviewed the ongoing clinical studies of these ADCs, highlighting their efficacy and safety profiles. Furthermore, we explored the potential of combining Trop-2-targeted ADCs with other therapeutic modalities, including immunotherapy, targeted therapies, and small molecule inhibitors. Notably, Trop-2-targeted ADCs have shown promise in reprogramming the tumor microenvironment through multiple signaling pathways, potentially enhancing antitumor immunity. This review aims to provide new insights and research directions for the development of innovative breast cancer therapies, offering potential solutions to improve treatment outcomes and quality of life for breast cancer patients.

Targeting SMYD2 inhibits angiogenesis and increases the efficiency of apatinib by suppressing EGFL7 in colorectal cancer

Angiogenesis is an essential factor affecting the occurrence and development of solid tumors. SET And MYND Domain Containing 2 (SMYD2) serves as an oncogene in various cancers. However, whether SMYD2 is involved in tumor angiogenesis remains unclear. Here, we report that SMYD2 expression is associated with microvessel density in colorectal cancer (CRC) tissues. SMYD2 promotes CRC angiogenesis in vitro and in vivo. Mechanistically, SMYD2 physically interacts with HNRNPK and mediates lysine monomethylation at K422 of HNRNPK, which substantially increases RNA binding activity. HNRNPK acts by binding and stabilizing EGFL7 mRNA. As an angiogenic stimulant, EGFL7 enhances CRC angiogenesis. H3K4me3 maintained by PHF8 mediates the abnormal overexpression of SMYD2 in CRC. Moreover, targeting SMYD2 blocks CRC angiogenesis in tumor xenografts. Treatment with BAY-598, a functional inhibitor of SMYD2, can also synergize with apatinib in patient-derived xenografts. Overall, our findings reveal a new regulatory axis of CRC angiogenesis and provide a potential strategy for antiangiogenic therapy.

Application basis of combining antiangiogenic therapy with radiotherapy and immunotherapy in cancer treatment

How to further optimize the combination of radiotherapy and immunotherapy is among the current hot topics in cancer treatment. In addition to adopting the preferred dose-fractionation of radiotherapy or the regimen of immunotherapy, it is also very promising to add antiangiogenic therapy to this combination. We expound the application basis of cancer radiotherapy combined with immunotherapy and antiangiogenic therapy.

Stimuli-responsive nanoassemblies for targeted delivery against tumor and its microenvironment

Despite the emergence of various cancer treatments, such as surgery, chemotherapy, radiotherapy, and immunotherapy, their use remains restricted owing to their limited tumor elimination efficacy and side effects. The use of nanoassemblies as delivery systems in nanomedicine for tumor diagnosis and therapy is flourishing. These nanoassemblies can be designed to have various shapes, sizes, and surface charges to meet the requirements of different applications. It is crucial for nanoassemblies to have enhanced delivery of payloads while inducing minimal to no toxicity to healthy tissues. In this review, stimuli-responsive nanoassemblies capable of combating the tumor microenvironment (TME) are discussed. First, various TME characteristics, such as hypoxia, oxidoreduction, adenosine triphosphate (ATP) elevation, and acidic TME, are described. Subsequently, the unique characteristics of the vascular and stromal TME are differentiated, and multiple barriers that have to be overcome are discussed. Furthermore, strategies to overcome these barriers for successful drug delivery to the targeted site are reviewed and summarized. In conclusion, the possible challenges and prospects of using these nanoassemblies for tumor-targeted delivery are discussed. This review aims at inspiring researchers to develop stimuli-responsive nanoassemblies for tumor-targeted delivery for clinical applications.

Role of Tumor Microenvironment in Cancer Stem Cells Resistance to Radiotherapy

Cancer is a chronic disorder that involves several elements of both the tumor and the host stromal cells. At present, the complex relationship between the various factors presents in the tumor microenvironment (TME) and tumor cells, as well as immune cells located within the TME, is still poorly known. Within the TME, the crosstalk of these factors and immune cells essentially determines how a tumor reacts to the treatment and how the tumor can ultimately be destroyed, remain dormant, or develop and metastasize. Also, in TME, reciprocal crosstalk between cancer-associated fibroblasts (CAFs), extracellular matrix (ECM), hypoxia-inducible factor (HIF) intensifies the proliferation capacity of cancer stem cells (CSCs). CSCs are subpopulation of cells that reside within the tumor bulk and have the capacity to self-renew, differentiate, and repair DNA damage. These characteristics make CSCs develop resistance to a variety of treatments, such as radiotherapy (RT). RT is a frequent and often curative treatment for local cancer which mediates tumor elimination by cytotoxic actions. Also, cytokines and growth factors that are released into TME, have been involved in the activation of tumor radioresistance and the induction of different immune cells, altering local immune responses. In this review, we discuss the pivotal role of TME in resistance of CSCs to RT.

Redox-sensitive hyaluronic acid-cholesterol nanovehicles potentiate efficient transmembrane internalization and controlled release for penetrated "full-line" inhibition of pre-metastatic initiation

Metastatic breast cancer is a major cause of cancer-related mortality worldwide. The tumor-specific penetration and triggered drug release for "full-line" inhibition of pre-metastatic initiation are of essential importance in improving mortality rates. Here, a crosslinked, redox-sensitive amphiphilic conjugate (cHLC) was constructed with a combination of features, including hyaluronic acid (HA)-mediated tumor active targeting, lipoic acid (LA) core-crosslinking based bio-stability and reducibility, and lipid raft anchoring-promoted HA-mediated endocytosis through cholesterol (CHO) modification for the penetrated co-delivery of paclitaxel (PTX) and the multi-targeted anti-metastatic agent, silibinin (SB). Resultantly, the nanodrug (cHLC/(PTX + SB)) demonstrated enhanced tumor cytoplasm-selective rapid drug delivery in a 4T1 model both in vitro and in vivo. The released SB efficiently sensitized cells to PTX treatment and inhibited the whole process of pre-metastatic initiation including epithelial-to-mesenchymal transition (EMT), local and blood vessel invasion. The exquisite design of this delivery system provides a deep insight into enhancing focus accessibility of multi-targeted drugs for an efficient inhibition of tumor metastasis.

Circular dumbbell miR-34a-3p and -5p suppresses pancreatic tumor cell-induced angiogenesis and activates macrophages

Angiogenesis is a tightly regulated biological process by which new blood vessels are formed from pre-existing blood vessels. This process is also critical in diseases such as cancer. Therefore, angiogenesis has been explored as a drug target for cancer therapy. The future of effective anti-angiogenic therapy lies in the intelligent combination of multiple targeting agents with novel modes of delivery to maximize therapeutic effects. Therefore, a novel approach is proposed that utilizes dumbbell RNA (dbRNA) to target pathological angiogenesis by simultaneously targeting multiple molecules and processes that contribute to angiogenesis. In the present study, a plasmid expressing miR-34a-3p and -5p dbRNA (db34a) was constructed using the permuted intron-exon method. A simple protocol to purify dbRNA from bacterial culture with high purity was also developed by modification of the RNASwift method. To test the efficacy of db34a, pancreatic cancer cell lines PANC-1 and MIA PaCa-2 were used. Functional validation of the effect of db34a on angiogenesis was performed on human umbilical vein endothelial cells using a tube formation assay, in which cells transfected with db34a exhibited a significant reduction in tube formation compared with cells transfected with scrambled dbRNA. These results were further validated in vivo using a zebrafish angiogenesis model. In conclusion, the present study demonstrates an approach for blocking angiogenesis using db34a. The data also show that this approach may be used to targeting multiple molecules and pathways.

Monitoring of tumor growth and vascularization with repetitive ultrasonography in the chicken chorioallantoic-membrane-assay

The chorioallantoic-membrane (CAM)-assay is an established model for in vivo tumor research. Contrary to rodent-xenograft-models, the CAM-assay does not require breeding of immunodeficient strains due to native immunodeficiency. This allows xenografts to grow on the non-innervated CAM without pain or impairment for the embryo. Considering multidirectional tumor growth, limited monitoring capability of tumor size is the main methodological limitation of the CAM-assay for tumor research. Enclosure of the tumor by the radiopaque eggshell and the small structural size only allows monitoring from above and challenges established imaging techniques. We report the eligibility of ultrasonography for repetitive visualization of tumor growth and vascularization in the CAM-assay. After tumor ingrowth, ultrasonography was repetitively performed in ovo using a commercial ultrasonographic scanner. Finally, the tumor was excised and histologically analyzed. Tumor growth and angiogenesis were successfully monitored and findings in ultrasonographic imaging significantly correlated with results obtained in histological analysis. Ultrasonography is cost efficient and widely available. Tumor imaging in ovo enables the longitudinal monitoring of tumoral development, yet allowing high quantitative output due to the CAM-assays simple and cheap methodology. Thus, this methodological novelty improves reproducibility in the field of in vivo tumor experimentation emphasizing the CAM-assay as an alternative to rodent-xenograft-models.

Cancer-associated fibroblast regulation of tumor neo-angiogenesis as a therapeutic target in cancer

Adequate blood supply is essential for tumor survival, growth and metastasis. The tumor microenvironment (TME) is dynamic and complex, comprising cancer cells, cancer-associated stromal cells and their extracellular products. The TME serves an important role in tumor progression. Cancer-associated fibroblasts (CAFs) are the principal component of stromal cells within the TME, and contribute to tumor neo-angiogenesis by altering the proteome and degradome. The present paper reviews previous studies of the molecular signaling pathways by which CAFs promote tumor neo-angiogenesis and highlights therapeutic response targets. Also discussed are potential strategies for antitumor neo-angiogenesis to improve tumor treatment efficacy.

Suppression of colorectal cancer liver metastasis by apolipoprotein(a) kringle V in a nude mouse model through the induction of apoptosis in tumor-associated endothelial cells

The formation of liver metastases in colorectal cancer patients is the primary cause of patient death. Current therapies directed at liver metastasis from colorectal cancer have had minimal impact on patient outcomes. Therefore, the development of alternative treatment strategies for liver metastasis is needed. In the present study, we demonstrated that recombinant human apolipoprotein(a) kringle V, also known as rhLK8, induced the apoptotic turnover of endothelial cells in vitro through the mitochondrial apoptosis pathway. The interaction of rhLK8 with glucose-regulated protein 78 (GRP78) may be involved in the induction of apoptosis because the inhibition of GRP78 by GRP78-specific antibodies or siRNA knockdown inhibited the rhLK8-mediated apoptosis of human umbilical vein endothelial cells in vitro. Next, to evaluate the effects of rhLK8 on angiogenesis and metastasis, an experimental model of liver metastasis was established by injecting a human colorectal cancer cell line, LS174T, into the spleens of BALB/c nude mice. The systemic administration of rhLK8 significantly suppressed liver metastasis from human colorectal cancer cells and improved host survival compared with controls. The combination of rhLK8 and 5-fluorouracil substantially increased these survival benefits compared with either therapy alone. Histological observation showed significant induction of apoptosis among tumor-associated endothelial cells in liver metastases from rhLK8-treated mice compared with control mice. Collectively, these results suggest that the combination of rhLK8 with conventional chemotherapy may be a promising approach for the treatment of patients with life-threatening colorectal cancer liver metastases.

Low-dose radiation induces antitumor effects and erythrocyte system hormesis

OBJECTIVE

Low dose radiation may stimulate the growth and development of animals, increase life span, enhance fertility, and downgrade the incidence of tumor occurrence.The aim of this study was to investigate the antitumor effect and hormesis in an erythrocyte system induced by low-dose radiation.

METHODS

Kunming strain male mice were subcutaneously implanted with S180 sarcoma cells in the right inguen as an experimental in situ animal model. Six hours before implantation, the mice were given 75mGy whole body X-ray radiation. Tumor growth was observed 5 days later, and the tumor volume was calculated every other day. Fifteen days later, all mice were killed to measure the tumor weight, and to observe necrotic areas and tumor-infiltration-lymphoreticular cells (TILs). At the same time, erythrocyte immune function and the level of 2,3-diphosphoglyceric acid (2,3- DPG) were determined. Immunohistochemical staining was used to detect the expression of EPO and VEGFR of tumor tissues.

RESULTS

The mice pre-exposed to low dose radiation had a lower tumor formation rate than those without low dose radiation (P < 0.05). The tumor growth slowed down significantly in mice pre-exposed to low dose radiation; the average tumor weight in mice pre-exposed to low dose radiation was lighter too (P < 0.05). The tumor necrosis areas were larger and TILs were more in the radiation group than those of the group without radiation. The erythrocyte immune function, the level of 2,3-DPG in the low dose radiation group were higher than those of the group without radiation (P < 0.05). After irradiation the expression of EPO of tumor tissues in LDR group decreased with time. LDR-24h, LDR-48h and LDR-72h groups were all statistically significantly different from sham-irradiation group. The expression of VEGFR also decreased, and LDR-24h group was the lowest (P < 0.05).

CONCLUSION

Low dose radiation could markedly increase the anti-tumor ability of the organism and improve the erythrocyte immune function and the ability of carrying O2. Low-dose total body irradiation, within a certain period of time, can decrease the expression of hypoxia factor EPO and VEGFR, which may improve the situation of tumor hypoxia and radiosensitivity of tumor itself.

MRI-based computational model of heterogeneous tracer transport following local infusion into a mouse hind limb tumor

Systemic drug delivery to solid tumors involving macromolecular therapeutic agents is challenging for many reasons. Amongst them is their chaotic microvasculature which often leads to inadequate and uneven uptake of the drug. Localized drug delivery can circumvent such obstacles and convection-enhanced delivery (CED)--controlled infusion of the drug directly into the tissue--has emerged as a promising delivery method for distributing macromolecules over larger tissue volumes. In this study, a three-dimensional MR image-based computational porous media transport model accounting for realistic anatomical geometry and tumor leakiness was developed for predicting the interstitial flow field and distribution of albumin tracer following CED into the hind-limb tumor (KHT sarcoma) in a mouse. Sensitivity of the model to changes in infusion flow rate, catheter placement and tissue hydraulic conductivity were investigated. The model predictions suggest that 1) tracer distribution is asymmetric due to heterogeneous porosity; 2) tracer distribution volume varies linearly with infusion volume within the whole leg, and exponentially within the tumor reaching a maximum steady-state value; 3) infusion at the center of the tumor with high flow rates leads to maximum tracer coverage in the tumor with minimal leakage outside; and 4) increasing the tissue hydraulic conductivity lowers the tumor interstitial fluid pressure and decreases the tracer distribution volume within the whole leg and tumor. The model thus predicts that the interstitial fluid flow and drug transport is sensitive to porosity and changes in extracellular space. This image-based model thus serves as a potential tool for exploring the effects of transport heterogeneity in tumors.

Interfering growth of malignant melanoma with Ang2-siRNA

To investigate the intervention therapy effect on the growth of malignant melanoma, we have made an observation of expression levels of Ang2 in malignant melanoma cells, which was transduced by small interfering RNA (Ang2-siRNA) of Ang2 in vitro and in vivo. We successfully constructed Ang2-siRNA lent virus, and constructed nude mice model by transplanting malignant melanoma. Ang2-siRNA lent virus inhibited Ang2 mRNA of malignant melanoma in vitro and in vivo, and inhibited malignant melanoma tumor growth at the same time. Ang2-siRNA lent virus can interfere expression levels of Ang2 in malignant melanoma cells, inhibit tumor growth, and silent Ang2 gene expression, which may pave a new way for clinical gene therapy of malignant melanoma.

Combination therapy of radiofrequency ablation and bevacizumab monitored with power Doppler ultrasound in a murine model of hepatocellular carcinoma

PURPOSE

The purpose of this study was to monitor tumour blood flow with power Doppler ultrasound following antiangiogenic therapy with bevacizumab in order to optimally time the application of radiofrequency (RF) ablation to increase ablation diameter.

MATERIALS AND METHODS

Athymic nude mice bearing human hepatocellular carcinoma xenografts were treated with bevacizumab and imaged daily with power Doppler ultrasound to quantify tumour blood flow. Mice were treated with RF ablation alone or in combination with bevacizumab at the optimal time, as determined by ultrasound. Ablation diameter was measured with histology and tumour microvascular density was calculated with immunohistochemistry. A computational thermal model of RF ablation was used to estimate ablation volume.

RESULTS

A maximum reduction of 27.8 ± 8.6% in tumour blood flow occurred on day 2 following antiangiogenic therapy, while control tumours increased 29.3 ± 17.1% (p < 0.05). Tumour microvascular density was similarly reduced by 45.1 ± 5.9% on day 2 following antiangiogenic therapy. Histology demonstrated a 13.6 ± 5.6% increase in ablation diameter (40 ± 21% increase in volume) consistent with a computational model.

CONCLUSION

Quantitative power Doppler ultrasound is a useful biomarker to monitor tumour blood flow following antiangiogenic treatment and to guide the application of RF ablation as a drug plus device combination therapy.

Targeted antivascular therapy with the apolipoprotein(a) kringle V, rhLK8, inhibits the growth and metastasis of human prostate cancer in an orthotopic nude mouse model

Antivascular therapy has emerged as a rational strategy to improve the treatment of androgen-independent prostate cancer owing to the necessity of establishing a vascular network for the growth and progression of the primary and metastatic tumor. We determined whether recombinant human apolipoprotein(a) kringle V, rhLK8, produces therapeutic efficacy in an orthotopic human prostate cancer animal model. Fifty thousand androgen-independent human prostate cancer cells (PC-3MM2) were injected into the prostate of nude mice. After 3 days, these mice were randomized to receive the vehicle solution (intraperitoneally [i.p.], daily), paclitaxel (8 mg/kg i.p., weekly), rhLK8 (50 mg/kg i.p., daily), or a combination of paclitaxel and rhLK8 for 4 weeks. Treatment with paclitaxel or rhLK8 alone did not show significant therapeutic effects on tumor incidence or on tumor size compared with the control group. The combination of rhLK8 and paclitaxel significantly reduced tumor size and incidence of lymph node metastasis. Significant reduction in microvessel density and cellular proliferation and induction of apoptosis of tumor cells, and tumor-associated endothelial cells, were also achieved. Similarly, PC-3MM2 tumors growing in the tibia showed significant suppression of tumor growth and lymph node metastasis by the combination treatment with rhLK8 and paclitaxel. The integrity of the bone was significantly preserved, and apoptosis of tumor cells and tumor-associated endothelial cells was increased. In conclusion, these results suggest that targeting the tumor microenvironment with the antivascular effect of rhLK8 combined with conventional cytotoxic chemotherapy could be a new and effective approach in the treatment of androgen-independent prostate cancer and their metastases.

Integrin-mediated cell-matrix interaction in physiological and pathological blood vessel formation

Physiological as well as pathological blood vessel formation are fundamentally dependent on cell-matrix interaction. Integrins, a family of major cell adhesion receptors, play a pivotal role in development, maintenance, and remodeling of the vasculature. Cell migration, invasion, and remodeling of the extracellular matrix (ECM) are integrin-regulated processes, and the expression of certain integrins also correlates with tumor progression. Recent advances in the understanding of how integrins are involved in the regulation of blood vessel formation and remodeling during tumor progression are highlighted. The increasing knowledge of integrin function at the molecular level, together with the growing repertoire of integrin inhibitors which allow their selective pharmacological manipulation, makes integrins suited as potential diagnostic markers and therapeutic targets.

The relationship between RGS5 expression and cancer differentiation and metastasis in non-small cell lung cancer

BACKGROUND

Regulator of G-protein signaling 5 (RGS5), a tissue-specific signal regulating molecular, plays important roles in the development of vasculature. Recently, we have found that the mRNA level of RGS5 was oppositely related with tumor metastasis in non-small cell lung cancer (NSCLC). However, the distribution of RGS5 in NSCLC and its significance need further study. We therefore investigated the expression of RGS5 in NSCLC, as well as its relationship with clinicopathologic parameters.

METHODS

Tumor tissues from 51 NSCLC patients were analyzed and expression of RGS5 in tumor tissues was examined by immunohistochemistry. Chi-square test (or Fisher's exact test), Breslow test and multivariate Cox regression model were performed for statistical analysis.

RESULTS

RGS5 were highly expressed in 47% (24/51) of NSCLC specimens. Expression of RGS5 was associated with tumor cell differentiation in NSCLC and low expression of RGS5 was strongly associated with cancer vasculature invasion and lymph node metastasis in NSCLC. Patients with high RGS5 expression in NSCLC had a prolonged progression free survival (15.0 months (95%CI: 6.1-23.9) vs. 6.0 months (95%CI: 1.3-10.7), P = 0.030).

CONCLUSION

RGS5 might be involved in cancer differentiation and metastasis in NSCLC. And it might be a candidate prognostic marker for PFS in NSCLC.

Recombinant human endostatin improves anti-tumor efficacy of paclitaxel by normalizing tumor vasculature in Lewis lung carcinoma

PURPOSE

Normalization of the tumor vasculature and microenvironment by several angiogenesis inhibitors has been reported. Given that recombinant human endostatin (rh-endostatin) is also an endogenous angiogenesis inhibitor, a comprehensive evaluation of the effects of rh-endostatin on tumor vasculature and microenvironment and chemotherapy sensitivity would be favorable.

METHODS

Multiple treatment schedules of the combination of rh-endostatin and paclitaxel were tested in Lewis lung carcinoma. Further, we monitored microvascular density, tumor hypoxic fraction, and collagen covered tumor vessels at three different time points following the treatment of rh-endostatin, as well as the transcription of angiogenesis related factors (vascular endothelial growth factor-A and thrombospondin-1) and vasculature markers (regulator of G-protein signaling 5 and platelet/endothelial cell adhesion molecule-1).

RESULTS

The anti-tumor efficacy of paclitaxel was significantly improved 7 days after the treatment of rh-endostatin. Tumor microvascular density was decreased by rh-endostatin, although it became even higher 7 days after termination of rh-endostatin. Non-necrotic hypoxic fraction was significantly reduced 7 days after treatment of rh-endostatin, accompanied with increased collagen covered tumor vessels and coverage of pericytes around endothelial cells. Rh-endostatin could transiently upregulate the transcription of thrombospondin-1 and modulate the imbalance between vascular endothelial growth factor-A and thrombospondin-1.

CONCLUSION

Rh-endostatin could normalize the tumor vasculature and microenvironment in Lewis lung carcinoma probably via modulation of the balance between vascular endothelial growth factor-A and thrombospondin-1. During the time of vascular normalization, paclitaxel treatment was found to have maximal effect on tumor growth delay.

Discrepancies between antiangiogenic and antitumor effects of recombinant human endostatin

It has been widely accepted that antiangiogenesis therapy could deprive tumor cells of nutrients and oxygen and suppress tumor growth. However, in the present study, Lewis lung carcinomas and A549 adenocarcinomas established in male C57BL/6 and BALB/c nude mice, respectively, were treated with recombinant human endostatin (rh-endostatin). Earlier studies document discrepancies in the antiangiogenic and antitumor outcomes of rh-endostatin treatment, at doses equivalent to clinical usage. Although there was no significant regression of tumor growth, tumor vasculature was widely disrupted within the first few days of treatment with rh-endostatin, as indicated by reduced blood perfusion (visualized by dynamic-contrast-enhanced magnetic resonance imaging) and reduced microvascular density. Interestingly, when rh-endostatin treatment was discontinued, there was an elevation in the diffusion of oxygen and tetramethylrhodamine isothiocyanate-dextran in both tumor classes, which was detected by hypoxyprobe (pimonidazole) and fluorescence microscopy. We conclude that the paradoxic outcomes in the antiangiogenic and antitumor properties of rh-endostatin might derive from the tumors' tolerance to antiangiogenesis inhibitors. Additionally, rh-endostatin might have the ability to transiently normalize tumor vasculature.

Combining radiation, immunotherapy, and antiangiogenesis agents in the management of cancer: the Three Musketeers or just another quixotic combination?

With the advent of new cancer therapies in the last few years, the goals of reducing disease burden and improving quality of life are frequently achieved. Yet despite the advances seen with numerous monotherapies, a multimodality approach that targets different aspects of tumor biology may yield the greatest clinical benefit for patients with late-stage disease. Many such strategies have been employed with varying degrees of success. The addition of immunotherapy to standard-of-care radiation therapy has shown evidence of efficacy in some preclinical models and in the clinical setting. However, exploiting these two modalities safely and effectively remains an ongoing challenge. It is feasible that the addition of another therapeutic modality could further enhance the antitumor effects of these treatments. The recent addition of angiogenesis inhibitors to the cancer treatment armamentarium represents an attractive option, especially since these agents have been shown to be most effective when combined with other therapies. This review examines preclinical and clinical data on the interaction between immunotherapy and radiation, and discusses the potential synergy between these two modalities and angiogenesis inhibitors.

The critical role of the bone microenvironment in cancer metastases

Bone metastatic disease is a late-stage event of many common cancers, such as those of prostate and breast. It is incurable and causes severe morbidity. Tumor and bone interact in a vicious cycle, where tumor-secreted factors stimulate bone cells, which in turn release growth factors and cytokines that act back on the tumor cells. Within the vicious cycle are many potential therapeutic targets for novel treatment of bone metastatic disease. Therapeutic strategies can be oriented to inhibit bone cells (osteoclasts and osteoblasts) or tumor responses to factors enriched in the bone microenvironment. Many publications, especially from pre-clinical animal models, show that this approach, especially combination treatments, can reduce tumor burden and tumor-derived bone lesions. This supports a novel paradigm: tumor growth can be effectively inhibited by targeting the bone and its microenvironment rather than the tumor itself alone.