Antiangiogenics and radiotherapy

SIRT in 2025

Selective internal radiation therapy represents an endovascular treatment option for patients with primary liver malignancies, in different clinical stages. Potential applications of this treatment are in early-stage hepatocellular carcinoma, as a curative option, or in combination with systemic treatments in intermediate and advanced-stages. This review, based on existing literature and ongoing trials, will focus on the future of this treatment in patients with hepatocellular carcinoma, in combination with systemic treatments, or with the use of new devices and technological developments; it will also describe new potential future indications and structural and organizational perspectives.

Intensity-modulated radiotherapy for hepatocellular carcinoma: dosimetric and clinical results

Since the introduction of 3-dimensional conformal radiotherapy (3DCRT), new radiotherapy techniques have expanded the indication of radiotherapy for the treatment of hepatocellular carcinoma (HCC), from the hitherto palliative to a now curative-intent purpose. Intensity-modulated radiotherapy (IMRT), currently the most advanced radiotherapy technique, is considered an attractive option for the treatment of HCC, and is more widely applied because it can deliver a higher dose to the tumor than 3DCRT while sparing surrounding normal organs. However, the advantages and potential disadvantages of IMRT for treating HCC have not been fully established. This article deals with three different IMRT techniques, including static IMRT and volumetric modulated arc therapy using conventional multileaf collimator (MLC) mounted linear accelerators, and helical IMRT using binary MLC mounted helical tomotherapy machine. We review dosimetric and clinical studies for these IMRT techniques for the treatment of HCC.

Silencing platelet-derived growth factor receptor-β enhances the radiosensitivity of C6 glioma cells in vitro and in vivo

Platelet-derived growth factor receptor (PDGFR)-β is an important tyrosine kinase and its downregulation has been reported to alter the radiosensitivity of glioma cells, although the underlying mechanism is unclear. In order to investigate the effect of PDGFR-β on the radiosensitivity of glioblastoma, the present study transfected C6 glioma cells with a PDGFR-β-specific small interfering (si)RNA expression plasmid, and downregulation of the expression of PDGFR-β in C6 glioma cells was confirmed by western blotting and immunohistochemical analysis. Clone formation assays and xenograft growth curves demonstrated that PDGFR-β-siRNA enhanced the radiosensitivity of C6 glioma cells in vitro and in vivo. Furthermore, MTT and xenograft growth curves demonstrated that PDGFR-β-siRNA inhibited the proliferation of C6 glioma cells in vitro and in vivo, and terminal deoxynucleotidyl transferase dUTP nick end-labeling and immunohistochemical analyses demonstrated that PDGFR-β-siRNA induced apoptosis and inhibited the expression of Ki-67, cyclin B1 and vascular endothelial growth factor in C6 glioma cell xenografts. Taken together, these results suggested that PDGFR-β may be used as a target for the radiosensitization of glioblastoma.

Low-dose radiotherapy and concurrent FOLFIRI-bevacizumab: a Phase II study

Aims: Low-dose radiation therapy (LDRT) can increase biological efficacy of chemotherapy. This Phase II trial evaluates LDRT plus FOLFIRI-bevacizumab (FOLFIRI-B) in metastatic colorectal cancer. Materials & methods: Primary objective: raising the clinical complete response rate from 5 to 25%. Secondary objectives: toxicity, progression-free survival. Patients underwent 12 FOLFIRI-B cycles plus two daily LDRT fractions (20 cGy/6 h interval) on each cycle. Statistical analysis was planned on 18 patients. Results: Results on 18 patients are reported. Specifically considering irradiated sites: 15/18 patients had a partial (11/18) or complete (4/18) response. Among 11 partial responders, three became a pathological CR after surgery. Grade 3–4 toxicity was recorded in two patients (11.1%). At median follow-up of 30 months (range: 8-50), 7/18 patients progressed in irradiated sites. Conclusion: Seven out of 18 patients (38.9%) had clinical or pathological CR in lesions treated with LDRT. Further studies on this newer treatment modality seem justified.

Hypoxia-activated chemotherapeutic TH-302 enhances the effects of VEGF-A inhibition and radiation on sarcomas

Background:

Human sarcomas with a poor response to vascular endothelial growth factor-A (VEGF-A) inhibition and radiation therapy (RT) have upregulation of hypoxia-inducible factor 1α (HIF-1α) and HIF-1α target genes. This study examines the addition of the hypoxia-activated chemotherapy TH-302 to VEGF-A inhibition and RT (a.k.a. trimodality therapy).

Methods:

Trimodality therapy was examined in two xenograft models and in vitro in tumour endothelial cells and sarcoma cell lines.

Results:

In both mouse models, VEGF-A inhibition and radiation showed greater efficacy than either therapy alone in slowing sarcoma growth. When TH-302 was added, this trimodality therapy completely blocked tumour growth with tumours remaining dormant for over 3 months after cessation of therapy. Trimodality therapy caused 2.6- to 6.2-fold more endothelial cell-specific apoptosis than bimodality therapies, and microvessel density and HIF-1α activity were reduced to 11–13% and 13–20% of control, respectively. When trimodality therapy was examined in vitro, increases in DNA damage and apoptosis were much more pronounced in tumour endothelial cells compared with that in sarcoma cells, especially under hypoxia.

Conclusions:

The combination of TH-302, VEGF-A inhibition, and RT is highly effective in preclinical models of sarcoma and is associated with increased DNA damage and apoptosis in endothelial cells and decreased HIF-1α activity.

Role of Akt in human malignant glioma: from oncogenesis to tumor aggressiveness

Gathering evidence has revealed that Akt signaling pathway plays an important role in glioma progression and aggressiveness. Among Akt kinases the most studied, Akt1, has been involved in many cellular processes that are in favor of cell malignancy. More recently, the actions of the two other isoforms, Akt2 and Akt3 have emerged in glioma. After a description of Akt pathway activation, we will explore the role of each isoform in malignant glioma that strengthens the current preclinical and clinical studies evaluating the impact of Akt pathway targeting in glioblastomas.

FOLFIRI-bevacizumab and concurrent low-dose radiotherapy in metastatic colorectal cancer: preliminary results of a phase I-II study

BACKGROUND

To evaluate the effectiveness of low-dose radiation therapy (LDRT) and FOLFIRI-bevacizumab (FOLFIRI-B) combination in metastatic colorectal cancer.

METHODS

The primary objective of the study is to raise the clinical complete response (CR) rate from 5% to 25%. Secondary objectives include toxicity and progression-free survival. Patients underwent 12 FOLFIRI-B cycles plus two daily LDRT (20 cGy/6-hour interval) on the first and second days of each cycle.

RESULTS

CR and toxicity of 10 patients are reported. Considering irradiated sites, 10/10 patients had clinical partial response (PR) (7/10) or CR (3/10). Three clinical PR patients subsequently underwent surgery and reported a pathological CR in the irradiated sites. Grade 3-4 toxicities rate was 30%. With a median follow-up of 29 months (range: 12-49 months), 2/10 progression of disease in irradiated sites and 3/5 in non-irradiated sites were observed.

CONCLUSIONS

The very high response rate requires urgent verification in a larger patient series.

Radiotherapeutic strategies in the management of hepatocellular carcinoma

Although potentially curative therapies for hepatocellular carcinoma (HCC) are well established, they are offered only to a limited number of patients. For advanced HCC, sorafenib is now the treatment of choice. Radiotherapy technology has evolved remarkably during the past decade and can be precisely delivered, thereby permitting higher doses to the tumor and reduced doses to surrounding normal tissues. According to the Korean Liver Cancer Study Group (KLCSG) practice guidelines, radiation therapy is considered appropriate for unresectable, locally advanced HCC without extrahepatic metastasis, Child-Pugh class A or B, and tumors occupying less than two thirds of the liver with level II evidence. In this review, we discuss the radiotherapeutic strategies for each clinical setting in patients with HCC.

On the selectivity and efficacy of defense peptides with respect to cancer cells

Here, we review potential determinants of the anticancer efficacy of innate immune peptides (ACPs) for cancer cells. These determinants include membrane-based factors, such as receptors, phosphatidylserine, sialic acid residues, and sulfated glycans, and peptide-based factors, such as residue composition, sequence length, net charge, hydrophobic arc size, hydrophobicity, and amphiphilicity. Each of these factors may contribute to the anticancer action of ACPs, but no single factor(s) makes an overriding contribution to their overall selectivity and toxicity. Differences between the anticancer actions of ACPs seem to relate to different levels of interplay between these peptide and membrane-based factors.

RGD modified albumin nanospheres for tumour vasculature targeting

Objectives

Cyclic arginine-glycine-aspartic acid (RGD) peptide-anchored sterically stabilized albumin nanospheres (RGD-SN) have been investigated for the selective and preferential presentation of carrier contents at angiogenic endothelial cells overexpressing avb3 integrins on and around tumour tissue. Their targetabilty was assessed.

Methods

Albumin nanospheres were formulated, conjugated with RGD/RAD peptide and characterized on the basis of size and size distribution. The control Arginine-Alanine-Aspartic acid (RAD) peptide-anchored sterically stabilized nanospheres (RAD-SN) and nanosphere with 5 mol% PEG (SN) without peptide conjugate were used for comparison with RGD-SN for in vitro cell binding, in vivo organ distribution and tumor angiogenesis studies.

Key findings

The average size of all nanospheres prepared was approximately 100 nm and maximum drug entrapment was 67.2 ± 5.2%. In-vitro endothelial cell binding of nanospheres exhibited 8-fold higher binding of RGD-SN to human umbilical vein endothelial cells in comparison with the SN and RAD-SN. RGD peptide-anchored nanospheres were significantly (P ≤ 0.01) effective in the prevention of lung metastasis, angiogenesis and in effective regression of tumours compared with free fluorouracil, SN and RAD-SN. Results indicated that cyclic RGD peptide-anchored sterically stabilized nanospheres bearing fluorouracil were significantly (P ≤ 0.01) active against primary tumour and metastasis than the nontargeted sterically stabilized nanospheres and free drug.

Conclusions

Cyclic RGD peptide-anchored sterically stabilized nanospheres appears promising for targeted cancer chemotherapeutics.

Resident endothelial cells surrounding damaged arterial endothelium reendothelialize the lesion

OBJECTIVE

To evaluate endothelial repair processes in denuded pial vessels to clarify mechanisms for reconstructing endothelium (because endothelial repair of the cerebral artery after its damage is critical for the prevention of thrombosis, the maintenance of vascular tone, and the protection of the brain by the blood-brain barrier).

METHODS AND RESULTS

Endothelial cells (ECs) in a 350-microm-long segment of the middle cerebral artery were damaged through a photochemical reaction. Tie2-green fluorescent protein transgenic mice were used for the identification of ECs. Six hours after the endothelial damage, ECs were detached from the luminal surface of the damaged artery, which was then covered with a platelet carpet. Within 24 hours, recovery of the denuded artery started at both edges, with EC elongation and migration. The repair rate was faster at the proximal edge than at the distal edge. Reendothelialization with EC proliferation peaked at 2 to 3 days and ended at 5 days, together with normalization of EC length, with no apparent involvement of foreign progenitor cells.

CONCLUSIONS

Our in vivo study demonstrated a stepwise reendothelialization process by resident ECs of the pial artery. The prevention of thrombosis, vasospasm, and treatment for blood-brain barrier dysfunction should be considered during the reendothelialization period.

Radiotherapy in combination with vascular-targeted therapies

BACKGROUND

Given the critical role of tumor vasculature in tumor development, considerable efforts have been spent on developing therapeutic strategies targeting the tumor vascular network. A variety of agents have been developed, with two general approaches being pursued. Antiangiogenic agents (AAs) aim to interfere with the process of angiogenesis, preventing new tumor blood vessel formation. Vascular-disrupting agents (VDAs) target existing tumor vessels causing tumor ischemia and necrosis. Despite their great therapeutic potential, it has become clear that their greatest clinical utility may lie in combination with conventional anticancer therapies. Radiotherapy is a widely used treatment modality for cancer with its distinct therapeutic challenges. Thus, combining the two approaches seems reasonable.

CONCLUSIONS

Strong biological rationale exist for combining vascular-targeted therapies with radiation. AAs and VDAs were shown to alter the tumor microenvironment in such a way as to enhance responses to radiation. The results of preclinical and early clinical studies have confirmed the therapeutic potential of this new treatment strategy in the clinical setting. However, concerns about increased normal tissue toxicity, have been raised.

Effects of irradiation on tumor cell survival, invasion and angiogenesis

Ionizing irradiation is a widely applied therapeutic method for the majority of solid malignant neoplasms, including brain tumors where, depending on localization, this might often be the only feasible primary intervention.Without doubt, it has been proved to be a fundamental tool available in the battlefield against cancer, offering a clear survival benefit in most cases. However, numerous studies have associated tumor irradiation with enhanced aggressive phenotype of the remaining cancer cells. A cell population manages to survive after the exposure, either because it receives sublethal doses and/or because it successfully utilizes the repair mechanisms. The biology of irradiated cells is altered leading to up-regulation of genes that favor cell survival, invasion and angiogenesis. In addition, hypoxia within the tumor mass limits the cytotoxicity of irradiation, whereas irradiation itself may worsen hypoxic conditions, which also contribute to the generation of resistant cells. Activation of cell surface receptors, such as the epidermal growth factor receptor, utilization of signaling pathways, and over-expression of cytokines, proteases and growth factors, for example the matrix metalloproteinases and vascular endothelial growth factor, protect tumor and non-tumor cells from apoptosis, increase their ability to invade to adjacent or distant areas, and trigger angiogenesis. This review will try to unfold the various molecular events and interactions that control tumor cell survival, invasion and angiogenesis and which are elicited or influenced by irradiation of the tumor mass, and to emphasize the importance of combining irradiation therapy with molecular targeting.

Akt signaling pathway: a target for radiosensitizing human malignant glioma

Radiation therapy plays a central role in the treatment of glioblastoma, but it is not curative due to the high tumor radioresistance. Phosphatidyl-inositol 3-kinase/protein kinase B (Akt) and Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) pathways serve to block the apoptosis process, keeping cells alive in very toxic environments such as chemotherapy or ionizing radiation. In the present study, from a panel of 8 human malignant glioma cell lines, investigations on the relationship between intrinsic radioresistance and Akt or STAT3 basal activation were done. Secondly, the impact of down-modulation of Akt or STAT3 signaling on in vitro intrinsic radiosensitivity was evaluated. Using a clonogenic cell survival assay, our results revealed a significant correlation between the basal Akt activation and the surviving fraction at 2 Gy (SF2). In contrast, no correlation was found between STAT3 activation and SF2. According to this, down-modulation of Akt with a specific chemical inhibitor (Akt inhibitor IV) demonstrated a significant enhancement of radiation sensitivity on glioma cells in a clonogenic survival assay. On the contrary, down-modulation of STAT3 signaling with a specific chemical inhibitor (JSI-124) or a neutralizing gp130 antibody failed to radiosensitize glioma cells. These data indicate that the Akt intercept node could be a more relevant therapeutic target than STAT3 for radiosensitizing human malignant glioma.

Angiogenic blockade and radiotherapy in hepatocellular carcinoma

PURPOSE

We report our preliminary experience of combining sunitinib and helical tomotherapy in patients with advanced HCC.

METHODS AND MATERIALS

Records of patients with advanced hepatocellular carcinoma (HCC) treated with helical tomotherapy and sunitinib after radiation therapy (RT) from March 2007 to August 2008 were retrospectively reviewed. We report acute toxicities, radiologic response, serial alpha-fetoprotein (AFP) kinetics, and survival.

RESULTS

Of 23 evaluable patients, 60% had >or=2 hepatic lesions, extrahepatic disease was present in 5 (21.7%), and all received 2 tablets (25 mg) of sunitinib at least 1 week before, during, and 2 weeks after RT. Thirteen patients continued maintenance sunitinib after RT until disease progression. Hypofractionated RT with a median target dose of 52.5 Gy/15 fractions was delivered. An objective response was achieved in 74% of patients. The 1-year survival rate was 70%, with median survival of 16 months. Multivariate analysis showed that maintenance sunitinib was the most significant factor for survival. The time to progression was 10 months in the maintenance group compared with 4 months in the control group. Eighteen out of 21 patients with elevated AFP (85.7%) had >or=50% decline of AFP within 2 months after RT. There were three episodes of upper gastrointestinal bleeding and one episode of pancreatitis; 10 patients had >or=Grade 2 elevation of liver enzymes, and 15 had >or=Grade 2 thrombocytopenia.

CONCLUSIONS

These preliminary results suggest that sunitinib and helical tomotherapy yield high Response Evaluation Criteria in Solid Tumors (RECIST) and AFP response rates in advanced HCC with an acceptable safety profile. Maintenance sunitinib after RT potentially prolongs survival. A randomized trial is warranted.

The mitogen-activated protein/extracellular signal-regulated kinase kinase 1/2 inhibitor AZD6244 (ARRY-142886) enhances the radiation responsiveness of lung and colorectal tumor xenografts

PURPOSE

Novel molecularly targeted agents, given in combination with radiotherapy, have the potential to increase tumor response rates and the survival of patients with lung cancer. AZD6244 is a potent and selective inhibitor of mitogen-activated protein kinase (MAPK) kinase 1/2 (MEK1/2), a critical enzyme within the MAPK/extracellular signal-regulated kinase (ERK) signaling pathway that regulates the proliferation and survival of tumor cells.

EXPERIMENTAL DESIGN

This study examined the potential benefit of combining AZD6244 with fractionated radiotherapy using human lung and colon carcinoma xenograft models.

RESULTS

AZD6244 reduced ERK phosphorylation in Calu-6 lung cancer cells in vitro. Administration of AZD6244 for 10 days (25 mg/kg twice daily p.o.) inhibited the tumor growth of Calu-6 xenografts, with regrowth occurring on cessation of drug treatment. When fractionated tumor-localized radiotherapy (5 x 2 Gy) was combined with AZD6244 treatment, the tumor growth delay was enhanced significantly when compared with either modality alone, and this effect was also seen in a colon tumor model. We examined the effect of inhibiting MEK1/2 on the molecular responses to hypoxia, a potential interaction that could contribute to radioresponsiveness. AZD6244 reduced hypoxia-inducible factor-specific transactivation in vivo, shown using Calu-6 dual clone cells that stably express a Firefly luciferase gene under the control of a hypoxia-driven promoter. Furthermore, hypoxia-inducible factor-1 alpha, GLUT-1, and vascular endothelial growth factor levels were reduced by AZD6244, and there was a significant decrease in vascular perfusion in the tumors given combination treatment when compared with the other treatment groups.

CONCLUSIONS

These data provide support for the clinical development of AZD6244 in combination with radiotherapy and indicate a potential role for AZD6244 in inhibiting the tumor hypoxia response.

Report from the Radiation Therapy Committee of the Southwest Oncology Group (SWOG): Research Objectives Workshop 2008

Strategic planning for the Radiation Therapy Committee of the Southwest Oncology Group (SWOG) is comprehensively evaluated every six years in an effort to maintain a current and relevant scientific focus, and to provide a standard platform for future development of protocol concepts. Participants in the 2008 Strategic Planning Workshop included clinical trial experts from multiple specialties, industry representatives from both pharmaceuticals and equipment manufacturers, and basic scientists. High-priority research areas such as image-guided radiation therapy for control of limited metastatic disease, analysis of biomarkers for treatment response and late toxicity, assessment of novel agents in combination with radiation, standardization of radiation target delineation, and the assessment of new imaging techniques to individualize cancer therapy, were discussed. Research priorities included clinical study designs featuring translational end points that identify patients most likely to benefit from combined modality therapy; intervention including combination radiation with standard chemotherapy; radiation with radiosensitizing molecular-targeted therapies; and stereotactic radiation for treatment of patients with regard to asymptomatic metastasis and radiation-induced tumor autoimmunity. The Committee concluded that the future research opportunities are among the most exciting to have developed in the last decade, and work is in progress to embark on these plans.

Radiosensitising agents for the radiotherapy of cancer: novel molecularly targeted approaches

BACKGROUND

The efficacy of radiotherapy (RT) for cancer treatment is limited by normal tissue toxicity and by the intrinsic or acquired radioresistance of many tumours. Therefore, continuing efforts are conducted to identify radiosensitising agents that preferentially sensitise tumour cells to the cytotoxic action of RT. Recent progresses in molecular oncology have uncovered an array of novel targets, which may be exploited for RT enhancement.

OBJECTIVE

To survey the patent literature of the past 4 years pertaining to the development of molecularly targeted agents as potential tumour radiosensitisers.

METHODS

Patents were searched with a set of relevant keywords using several search engines. A Medline search on the same topics was performed in parallel.

RESULTS/CONCLUSION

A total of 48 patents/applications were selected. These concerned agents target molecular components of pathways involved in DNA damage repair, cell growth and survival signalling, apoptosis modulation and tumour angiogenesis. Current trials of some of these agents may reveal their value as clinical radiosensitisers.