Dynamics of tumor hypoxia in response to patupilone and ionizing radiation

Tumor hypoxia and radiotherapy: A major driver of resistance even for novel radiotherapy modalities

Hypoxia in solid tumors is an important predictor of poor clinical outcome to radiotherapy. Both physicochemical and biological processes contribute to a reduced sensitivity of hypoxic tumor cells to ionizing radiation and hypoxia-related treatment resistances. A conventional low-dose fractionated radiotherapy regimen exploits iterative reoxygenation in between the individual fractions, nevertheless tumor hypoxia still remains a major hurdle for successful treatment outcome. The technological advances achieved in image guidance and highly conformal dose delivery make it nowadays possible to prescribe larger doses to the tumor as part of single high-dose or hypofractionated radiotherapy, while keeping an acceptable level of normal tissue complication in the co-irradiated organs at risk. However, we insufficiently understand the impact of tumor hypoxia to single high-doses of RT and hypofractionated RT. So-called FLASH radiotherapy, which delivers ionizing radiation at ultrahigh dose rates (> 40 Gy/sec), has recently emerged as an important breakthrough in the radiotherapy field to reduce normal tissue toxicity compared to irradiation at conventional dose rates (few Gy/min). Not surprisingly, oxygen consumption and tumor hypoxia also seem to play an intriguing role for FLASH radiotherapy. Here we will discuss the role of tumor hypoxia for radiotherapy in general and in the context of novel radiotherapy treatment approaches.

Low-Cost, High-Pressure-Synthesized Oxygen-Entrapping Materials to Improve Treatment of Solid Tumors

Tumor hypoxia drives resistance to many cancer therapies, including radiotherapy and chemotherapy. Methods that increase tumor oxygen pressures, such as hyperbaric oxygen therapy and microbubble infusion, are utilized to improve the responses to current standard-of-care therapies. However, key obstacles remain, in particular delivery of oxygen at the appropriate dose and with optimal pharmacokinetics. Toward overcoming these hurdles, gas-entrapping materials (GeMs) that are capable of tunable oxygen release are formulated. It is shown that injection or implantation of these materials into tumors can mitigate tumor hypoxia by delivering oxygen locally and that these GeMs enhance responsiveness to radiation and chemotherapy in multiple tumor types. This paper also demonstrates, by comparing an oxygen (O2 )-GeM to a sham GeM, that the former generates an antitumorigenic and immunogenic tumor microenvironment in malignant peripheral nerve sheath tumors. Collectively the results indicate that the use of O2 -GeMs is promising as an adjunctive strategy for the treatment of solid tumors.

The ADAM17-directed Inhibitory Antibody MEDI3622 Antagonizes Radiotherapy-induced VEGF Release and Sensitizes Non-Small Cell Lung Cancer for Radiotherapy

The cellular response to ionizing radiation (IR) depends on tumor cell and microenvironmental factors. Here, we investigated the role of IR-induced ADAM17 matrix metalloproteinase activity for the intercellular communication between tumor cells and the tumor vasculature in non-small cell lung cancer (NSCLC) tumor models. Factors shed by ADAM17 from NSCLC tumor cells (A549, H358) and relevant for endothelial cell migration were investigated using transwell migration assays, ELISA, and flow cytometry. Tumor angiogenesis-related endpoints were analyzed with the chorio-allantoic membrane assay and in murine NSCLC tumor models. Efficacy-oriented experiments were performed in a murine orthotopic NSCLC tumor model using irradiation with an image-guided small-animal radiotherapy platform alone and in combination with the novel ADAM17-directed antibody MEDI3622. In vitro, VEGF was identified as the major factor responsible for IR-induced and ADAM17-dependent endothelial cell migration toward attracting tumor cells. IR strongly enhanced tumor cell-associated ADAM17 activity, released VEGF in an ADAM17-dependent manner, and thereby coordinated the communication between tumor and endothelial cells. In vivo, tumor growth and microvessel size and density were strongly decreased in response to the combined treatment modality of IR and MEDI3622 but not by either treatment modality alone and thus suggest that the supra-additive effect of the combined treatment modality is in part due to abrogation of the ADAM17-mediated IR-induced protective effect on the tumor vasculature. Furthermore, we demonstrate that the novel ADAM17-inhibitory antibody MEDI3622 potently improves the radiotherapy response of NSCLC.

Significance

The tumor response to radiotherapy is influenced by several factors of the tumor microenvironment. We demonstrate that inhibition of the sheddase ADAM17 by the novel antibody MEDI3622 reduces IR-induced VEGF release from tumor cells relevant for endothelial cell migration and vasculature protection, thereby enhancing radiotherapy treatment outcome of NSCLC.

Tumor Oxygenation by Myo-Inositol Trispyrophosphate Enhances Radiation Response

PURPOSE

Tumor hypoxia is a major limiting factor for successful radiation therapy outcomes, with hypoxic cells being up to 3-fold more radiation resistant than normoxic cells; tumor hypoxia creates a tumor microenvironment that is hostile to immune response. Thus, pharmaceutical-induced tumor oxygenation before radiation therapy represents an interesting method to enhance the efficacy of radiation therapy. Myo-inositol trispyrophosphate (ITPP) triggers a decrease in the affinity of oxygen to hemoglobin, which leads to an increased release of oxygen upon tissue demand, including in hypoxic tumors.

METHODS AND MATERIALS

The combined treatment modality of high-dose bolus ITPP with a single high-dose fraction of ionizing radiation (IR) was investigated for its mechanics and efficacy in multiple preclinical animal tumor models in immunocompromised and immunocompetent mice. The dynamics of tumor oxygenation were determined by serial hypoxia-oriented bioimaging. Initial and residual DNA damage and the integrity of the tumor vasculature were quantified on the immunohistochemical level in response to the different treatment combinations.

RESULTS

ITPP application did not affect tumor growth as a single treatment modality, but it rapidly induced tumor oxygenation, as demonstrated by in vivo imaging, and significantly reduced tumor growth when combined with IR. An immunohistochemical analysis of γH2AX foci demonstrated increased initial and residual IR-induced DNA damage as the primary mechanism for radiosensitization within initially hypoxic but ITPP-oxygenated tumor regions. Scheduling experiments revealed that ITPP increases the efficacy of ionizing radiation only when applied before radiation therapy. Irradiation alone damaged the tumor vasculature and increased tumor hypoxia, which were both prevented by combined treatment with ITPP. Interestingly, the combined treatment modality also promoted increased immune cell infiltration.

CONCLUSIONS

ITPP-mediated tumor oxygenation and vascular protection triggers immediate and delayed processes to enhance the efficacy of ionizing radiation for successful radiation therapy.

Comprehensive circular RNA profiling identifies CircFAM120A as a new biomarker of hypoxic lung adenocarcinoma

Background

Hypoxia is crucial in the initiation and progression of tumor metastasis. Circular RNAs (CircRNAs) comprise a novel group of non-coding, RNase R resistant and regulatory RNAs which are generated by 'back-splicing' processes. However, the characterization and function of circRNAs in hypoxic cancer cells remain unknown.

Methods

High throughput RNA-seq assay was performed in lung adenocarcinoma cells (A549) under either normoxic or hypoxic conditions. Bioinformatic analysis of differentially expressed circRNAs was conducted and their target genes were predicted and partially confirmed.

Results

Hypoxia increased the expression of hypoxia-inducible factor 1 alpha (HIF-1α) and its downstream genes in A549 cells and enhanced cell migration ability. Comprehensive analysis of global circRNAs expression profiles of A549 identified a total of 558 circRNAs candidates, among which 65 circRNAs were differentially expressed (35 upregulated and 30 downregulated) in hypoxic cancer cells. The difference in their circRNA expressions were compared by computational analysis and circRNA-miRNA networks were constructed. We further characterized one circRNA (hsa_circ_0008193) derived from the FAM120A gene and renamed it as circFAM120A. The expression of circFAM120A, as validated by reverse transcription polymerase chain reaction, was significantly downregulated in both hypoxic A549 and lung cancer tissue from patients with lymph node metastasis. Gene ontology (GO) enrichment analysis and KEGG pathway analysis revealed that circFAM120A may participate in lung cancer development.

Conclusions

CircRNAs profiles were altered in lung adenocarcinoma under hypoxia and circFAM120A may have the potential to be a new biomarker of lung adenocarcinoma hypoxia.

Predictive value of LDH kinetics in bevacizumab treatment and survival of patients with advanced NSCLC

Background

The combination of bevacizumab and chemotherapy is still one of the standard treatments for advanced non-small-cell lung cancer (NSCLC) patients in the new era of targeted therapy. Although a high level of baseline lactate dehydrogenase (LDH) was found to predict survival benefit from bevacizumab in patients with metastatic colorectal cancer, the predictive value of serum level of LDH in NSCLC patients treated with bevacizumab has not been investigated yet. Moreover, dynamic evaluation of serum level of LDH changes may be more informative and promising in predicting patients' prognosis. We thus sought to analyze LDH kinetics and evaluate its predictive role in the response and survival of advanced NSCLC patients treated with bevacizumab.

Method

We retrospectively collected and analyzed a total of 161 advanced NSCLC patients who had undergone treatment with bevacizumab. Univariate and multivariate logistic regression analyses of serum level of LDH were used for response analyses, and Cox models for both overall survival (OS) and progression-free survival analyses (PFS). Longitudinal analysis of LDH was performed using a mixed-effect regression model.

Results

On multivariate Cox models, increase of serum level of LDH after 4 cycles with bevacizumab (INC4) treatment was shown to be the independent risk factor for OS (hazard ratio =2.17, 95% CI: 1.21-3.90, P=0.009), and the serum level of LDH after 2 cycles (LDH2) and the increase of LDH after 6 cycles with bevacizumab (INC6) treatment were the predictive factors for PFS (hazard ratio =2.33, 95% CI: 1.38-3.93, P=0.001; hazard ratio =1.96, 95% CI: 1.27-3.03, P=0.002, respectively). Patients with increase of serum level of LDH after 2 cycles of treatment with bevacizumab (INC2) (odds ratio =3.75, 95% CI: 1.83-7.68, P<0.001) were more likely to attain stable disease/progressive disease on multivariate logistic regression analyses, while patients with complete response (CR)/partial response (PR) experienced a reduction of serum level of LDH every 2 cycles (Coef =-0.076, std error =0.017, P<0.001) over time.

Conclusion

Dynamic changes of LDH were superior to baseline LDH in predicting prognosis of NSCLC patients treated with bevacizumab. Serum level of LDH reducing over time was a potential biomarker for patients to achieve good clinical response (CR/PR) to bevacizumab.

The hypoxia-activated prodrug evofosfamide in combination with multiple regimens of radiotherapy

The promising treatment combination of ionizing radiation (IR) with a hypoxia-activated prodrug (HAP) is based on biological cooperation. Here we investigated the hypoxia-activated prodrug evofosfamide in combination with different treatment regimens of IR against lung A549- and head&neck UT-SCC-14-derived tumor xenografts. DNA damage-related endpoints and clonogenic cell survival of A549 and UT-SCC-14 carcinoma cells were probed under normoxia and hypoxia.Evofosfamide (TH-302) induced DNA-damage and a dose-dependent antiproliferative response in A549 cells on cellular pretreatment under hypoxia, and supra-additively reduced clonogenic survival in combination with IR. Concomitant treatment of A549-derived tumor xenografts with evofosfamide and fractionated irradiation induced the strongest treatment response in comparison to the corresponding neoadjuvant and adjuvant regimens. Adjuvant evofosfamide was more potent than concomitant and neoadjuvant evofosfamide when combined with a single high dose of IR. Hypoxic UT-SCC-14 cells and tumor xenografts thereof were resistant to evofosfamide alone and in combination with IR, most probably due to reduced P450 oxidoreductase expression, which might act as major predictive determinant of sensitivity to HAPs.In conclusion, evofosfamide with IR is a potent combined treatment modality against hypoxic tumors. However, the efficacy and the therapeutic outcome of this combined treatment modality is, as indicated here in preclinical tumor models, dependent on scheduling parameters and tumor type, which is most probably related to the status of respective HAP-activating oxidoreductases. Further biomarker development is necessary for the launch of successful clinical trials.

Selective portal vein injection for the design of syngeneic models of liver malignancy

Liver metastases are the most frequent cause of death due to colorectal cancer (CRC). Syngeneic orthotopic animal models, based on the grafting of cancer cells or tissue in host liver, are efficient systems for studying liver tumors and their (patho)physiological environment. Here we describe selective portal vein injection as a novel tool to generate syngeneic orthotopic models of liver tumors that avoid most of the weaknesses of existing syngeneic models. By combining portal vein injection of cancer cells with the selective clamping of distal liver lobes, tumor growth is limited to specific lobes. When applied on MC-38 CRC cells and their mouse host C57BL6, selective portal vein injection leads with 100% penetrance to MRI-detectable tumors within 1 wk, followed by a steady growth until the time of death (survival ∼7 wk) in the absence of extrahepatic disease. Similar results were obtained using CT-26 cells and their syngeneic Balb/c hosts. As a proof of principle, lobe-restricted liver tumors were also generated using Hepa1-6 (C57BL6-syngeneic) and TIB-75 (Balb/c-syngeneic) hepatocellular cancer cells, demonstrating the general applicability of selective portal vein injection for the induction of malignant liver tumors. Selective portal vein injection is technically straightforward, enables liver invasion via anatomical routes, preserves liver function, and provides unaffected liver tissue. The tumor models are reproducible and highly penetrant, with survival mainly dependent on the growth of lobe-restricted liver malignancy. These models enable biological studies and preclinical testing within short periods of time.

Combined treatment strategies for microtubule stabilizing agent-resistant tumors

BACKGROUND

Resistance to microtubule-stabilizing agents is a major hurdle for successful cancer therapy. We investigated combined treatment of microtubule-stabilizing agents (MSAs) with inhibitors of angiogenesis to overcome MSA resistance.

METHODS

Treatment regimens of clinically relevant MSAs (patupilone and paclitaxel) and antiangiogenic agents (everolimus and bevacizumab) were investigated in genetically defined MSA-resistant lung (A549EpoB40) and colon adenocarcinoma (SW480) tumor xenografts in nude mice (CD1-Foxn1<nu>, ICRnu; 5-14 per group). Tumor growth delays were calculated by Kaplan-Meier analysis with Holm-Sidak tests. All statistical tests were two-sided.

RESULTS

Inhibition of mTOR-kinase by everolimus only minimally reduced the proliferative activity of β tubulin-mutated lung adenocarcinoma cells alone and in combination with the MSA patupilone, but everolimus inhibited expression and secretion of vascular endothelial growth factor (VEGF) from these cells. mTOR-kinase inhibition strongly sensitized tumor xenografts derived from these otherwise MSA-resistant tumor cells to patupilone. Tumors treated with the combined modality of everolimus and patupilone had statistically significantly reduced tumor volume and stronger tumor growth delay (16.2 ± 1.01 days) than control- (7.7 ± 0.3 days, P = .004), patupilone- (10 ± 0.97 days, P = .009), and everolimus-treated (10.6 ± 1.4 days, P = .014) tumors. A combined treatment modality with bevacizumab also resensitized this MSA-refractory tumor model to patupilone. Treatment combination also strongly reduced microvessel density, corroborating the relevance of VEGF targeting for the known antivasculature-directed potency of MSA alone in MSA-sensitive tumor models. Resensitization to MSAs was also probed in P glycoprotein-overexpressing SW480-derived tumor xenografts. Different bevacizumab regimens also sensitized this otherwise-resistant tumor model to clinically relevant MSA paclitaxel.

CONCLUSIONS

A treatment combination of MSAs with antiangiogenic agents is potent to overcome tumor cell-linked MSA resistance and should be considered as strategy for MSA-refractory tumor entities.

Ionizing radiation induces tumor cell lysyl oxidase secretion

Background

Ionizing radiation (IR) is a mainstay of cancer therapy, but irradiation can at times also lead to stress responses, which counteract IR-induced cytotoxicity. IR also triggers cellular secretion of vascular endothelial growth factor, transforming growth factor β and matrix metalloproteinases, among others, to promote tumor progression. Lysyl oxidase is known to play an important role in hypoxia-dependent cancer cell dissemination and metastasis. Here, we investigated the effects of IR on the expression and secretion of lysyl oxidase (LOX) from tumor cells.

Methods

LOX-secretion along with enzymatic activity was investigated in multiple tumor cell lines in response to irradiation. Transwell migration assays were performed to evaluate invasive capacity of naïve tumor cells in response to IR-induced LOX. In vivo studies for confirming IR-enhanced LOX were performed employing immunohistochemistry of tumor tissues and ex vivo analysis of murine blood serum derived from locally irradiated A549-derived tumor xenografts.

Results

LOX was secreted in a dose dependent way from several tumor cell lines in response to irradiation. IR did not increase LOX-transcription but induced LOX-secretion. LOX-secretion could not be prevented by the microtubule stabilizing agent patupilone. In contrast, hypoxia induced LOX-transcription, and interestingly, hypoxia-dependent LOX-secretion could be counteracted by patupilone. Conditioned media from irradiated tumor cells promoted invasiveness of naïve tumor cells, while conditioned media from irradiated, LOX- siRNA-silenced cells did not stimulate their invasive capacity. Locally applied irradiation to tumor xenografts also increased LOX-secretion in vivo and resulted in enhanced LOX-levels in the murine blood serum.

Conclusions

These results indicate a differential regulation of LOX-expression and secretion in response to IR and hypoxia, and suggest that LOX may contribute towards an IR-induced migratory phenotype in sublethally-irradiated tumor cells and tumor progression.