Hypoxia-directed Therapy Research Articles

An Engineered Design of Self-Assembly Nanomedicine Guided by Molecular Dynamic Simulation for Photodynamic and Hypoxia-Directed Therapy.

To overcome the hypoxia barrier in tumor therapy, a hypoxia-activated prodrug of docetaxel (DTX-PNB) was synthesized and self-assembled with indocyanine green (ICG), forming a combination nanomedicine ISDNN. With the guidance of molecular dynamic simulation, the ISDNN construction could be accurately controlled, achieving uniform size distribution and high drug loading up to 90%. Within the hypoxic tumor environment, ISDNN exerted ICG-mediated photodynamic therapy and aggravated hypoxia to boost DTX-PNB activation for chemotherapy, enabling enhanced antitumor efficacy.

Paired 18F-Fluorodeoxyglucose (18F-FDG), and 64Cu-Copper(II)-diacetyl-bis(N(4)-methylthiosemicarbazone) (64Cu-ATSM) PET Scans in Dogs with Spontaneous Tumors and Evaluation for Hypoxia-Directed Therapy.

Hypoxia is associated with neoplastic tissue, protecting cancer cells from death by irradiation and chemotherapy. Identification of hypoxic volume of tumors could optimize patient selection for hypoxia-directed medical, immunological, and radiation therapies. Clostridium novyi-NT (CNV-NT) is an oncolytic bacterium derived from attenuated wild-type Clostridium novyi spores, which germinates exclusively in the anaerobic core of tumors with low-oxygen content. The hypothesis was that 64Cu-ATSM would localize to regions of hypoxia, and that greater hypoxic volume would result in greater germination of Clostridium novyi-NT (CNV-NT). Tumor-bearing companion dogs were recruited to a veterinary clinical trial. Dogs received a CT scan, 18F-FDG PET scan (74 MBq) and 64Cu-ATSM PET scan (74 MBq). Scan regions of interest were defined as the highest 20% of counts/voxel for each PET scan, and regions with voxels overlapping between the two scans. Maximum standardized uptake value (MaxSUV) and threshold volume were calculated. Direct oximetry was performed in select tumors. Tumor types evaluated included nerve sheath tumor (10), apocrine carcinoma (1), melanoma (3) and oral sarcoma (6). MaxSUVATSM ranged from 0.3-6.6. Measured oxygen tension ranged from 0.05-89.9 mmHg. Inverse of MaxSUVATSM had a linear relationship with oxygen tension (R2 = 0.53, P = 0.0048). Hypoxia <8 mmHg was associated with an SUVATSM > 1.0. Hypoxic volume ranged from 0 to 100% of gross tumor volume (GTV) and MaxSUVATSM was positively correlated with hypoxic volume (R = 0.674; P = 0.0001), but not GTV (P = 0.182). Tumor hypoxic volume was heterogeneous in location and distribution. 64Cu-ATSM-avid regions were associated with differential CT attenuation. Hypoxic volume did not predict CNV-NT germination. 64Cu-ATSM PET scanning predicts hypoxia patterns within spontaneously occurring tumors of dogs as measured by direct oxymetry. Total tumor volume does not accurately predict degree or proportion of tumor hypoxia.

SP-0137: Personalized medicine in the context of hypoxia-directed therapy

SP-0137: Personalized medicine in the context of hypoxia-directed therapy

Quantitative Visualization of Hypoxia and Proliferation Gradients Within Histological Tissue Sections.

The formation of hypoxic microenvironments within solid tumors is known to contribute to radiation resistance, chemotherapy resistance, immune suppression, increased metastasis, and an overall poor prognosis. It is therefore crucial to understand the spatial and molecular mechanisms that contribute to tumor hypoxia formation to improve the efficacy of radiation treatment, develop hypoxia-directed therapies, and increase patient survival. The objective of this study is to present a number of complementary novel methods for quantifying tumor hypoxia and proliferation in multiplexed immunofluorescence images, especially in relation to the location of perfused blood vessels. A standard marker analysis strategy is to take a positive pixel count approach, in which a threshold for positive stain is used to compute a positive area fraction for hypoxia. This work is a reassessment of that approach, utilizing not only cell segmentation but also distance to nearest blood vessel in order to incorporate spatial information into the analysis. We describe a reproducible pipeline for the visualization and quantitative analysis of hypoxia using a vessel distance analysis approach. This methodological pipeline can serve to further elucidate the relationship between vessel distance and microenvironment-linked markers such as hypoxia and proliferation, can help to quantify parameters relating to oxygen consumption and hypoxic tolerance in tissues, as well as potentially serve as a hypothesis generating tool for future studies testing hypoxia-linked markers.

ONECUT2 is a driver of neuroendocrine prostate cancer

Neuroendocrine prostate cancer (NEPC), a lethal form of the disease, is characterized by loss of androgen receptor (AR) signaling during neuroendocrine transdifferentiation, which results in resistance to AR-targeted therapy. Clinically, genomically and epigenetically, NEPC resembles other types of poorly differentiated neuroendocrine tumors (NETs). Through pan-NET analyses, we identified ONECUT2 as a candidate master transcriptional regulator of poorly differentiated NETs. ONECUT2 ectopic expression in prostate adenocarcinoma synergizes with hypoxia to suppress androgen signaling and induce neuroendocrine plasticity. ONEUCT2 drives tumor aggressiveness in NEPC, partially through regulating hypoxia signaling and tumor hypoxia. Specifically, ONECUT2 activates SMAD3, which regulates hypoxia signaling through modulating HIF1α chromatin-binding, leading NEPC to exhibit higher degrees of hypoxia compared to prostate adenocarcinomas. Treatment with hypoxia-activated prodrug TH-302 potently reduces NEPC tumor growth. Collectively, these results highlight the synergy between ONECUT2 and hypoxia in driving NEPC, and emphasize the potential of hypoxia-directed therapy for NEPC patients.

Clinical characterization of hypoxia in pancreatic ductal adenocarcinoma (PDAC) by 18F-FAZA PET and pimonidazole.

4049 Background: We previously demonstrated correlation between hypoxia and aggressive tumor biology in orthotopic, patient-derived pancreatic xenografts (Chang et al. Cancer Res 2011). With the development of hypoxia-directed therapies, there is a need to understand the range and relevance of hypoxia in PDAC patients. We therefore launched two complementary clinical trials using 2-nitroimidazole-based hypoxia probes. Methods: PIMO-PANC involves pre-operative administration of pimonidazole to patients (pts) undergoing PDAC resection. Hypoxic percent (HP) of tumors is determined by semi-automated image analysis (on Aperio’s Genie) of multiple histological sections stained for pimonidazole by immunohistochemistry (IHC). FAZA-PANC uses the positron emission tomography (PET) tracer fluoroazomycin arabinoside (18F-FAZA) to evaluate hypoxia by functional imaging. 2 hours post-injection of (5.2 MBq/kg) 18F-FAZA, static scans are acquired followed by computed tomography for anatomic registration. Skeletal muscle is a non-hypoxic reference tissue to define standardized uptake values (SUV), tumor to muscle uptake ratios (T/M’s) and a threshold for hypoxia. Results: PIMO-PANC has enrolled 29 pts and FAZA-PANC 16. IHC analysis of the first 10 pt tumors demonstrates considerable intra- and inter-tumoral heterogeneity of hypoxia (HP: 1 to 26% across pt tumors); minimal hypoxia (&lt; 5%) was observed in 3 pts. 18F-FAZA-PET in the first 11 pts demonstrates SUVmax from 1.02 to 1.83, median T/M's from 0.84 to 1.31. A threshold of 1.27 SUVmax defines HP of 0 to 60% with minimal hypoxia (&lt;10%) in 5 pts. Conclusions: There is significant heterogeneity of hypoxia across the spectrum of clinical PDAC (local to metastatic disease) using the 2-nitroimidazole hypoxia probes pimonidazole and 18F-FAZA. Given the intra-tumoral heterogeneity of hypoxia by histopathology, functional imaging is the preferred method to assess hypoxia in PDAC patients. Importantly, both methods identified a group of PDAC tumors with low levels of hypoxia. This is relevant to the on-going development of hypoxia-targeting strategies. Accrual to PIMO-PANC is on-going and will address the prognostic relevance of hypoxia in PDAC. Clinical trial information: NCT01542177 and NCT01248637.

Hypoxia and Radiation Therapy: Past History, Ongoing Research, and Future Promise

Tumor hypoxia influences the outcome of treatment with radiotherapy, chemotherapy and even surgery, not only for the treatment of large bulky tumors with extensive necrosis, but also in the treatment of very small primary tumors and recurrences, micrometastases, and surgical margins with microscopic tumor involvement. Because hypoxic tumor cells are resistant to radiation and to many anticancer drugs, many approaches to circumventing the therapeutic resistance induced by hypoxia have been examined in laboratory studies and clinical trials. In this review, these approaches and the results of past laboratory and clinical studies are described and the limitations of the past agents and their testing are discussed. We describe the importance of new technologies for measuring hypoxia in human tumors, which allow assessment of pretreatment tumor oxygen levels and changes in hypoxia over the course of prolonged treatment regimens. These offer the possibility of improving the design of clinical trials and the selection of patients who will benefit from hypoxia-directed therapies, as well as the possibility of facilitating the development of better agents and regimens for use in hypoxia-directed therapy. We also discuss how the improved understanding of the abnormal vascular beds in solid tumors and of the effects of hypoxia and related microenvironmental insults, resulting from recent and ongoing research, offers the potential for finding new therapeutic targets, that may lead to the development of new agents and novel therapeutic approaches for selectively targeting cells in the adverse microenvironments within solid tumors.

Pretreatment 18F-FAZA PET Predicts Success of Hypoxia-Directed Radiochemotherapy Using Tirapazamine

We evaluated the predictive value of PET using the hypoxia tracer (18)F-fluoroazomycin arabinoside ((18)F-FAZA) for success of radiotherapy in combination with tirapazamine, a specific cytotoxin for hypoxic cells. Imaging was performed on EMT6 tumor-bearing nude mice before allocating mice into 4 groups: radiochemotherapy (RCT: 8 fractions of 4.5 Gy within 4 d combined with tirapazamine, 14 mg/kg), radiotherapy alone (RT), chemotherapy alone (tirapazamine) (CHT), or control. Treatment success was assessed by several tumor growth assays, including tumor growth time from 70 to 500 microL and absolute growth delay (aGD). The median pretreatment (18)F-FAZA tumor-to-background ratio served as a discriminator between "hypoxic" and "normoxic" tumors. The mean tumor growth was significantly accelerated in hypoxic control tumors (growth time from 70 to 500 microL, 11.0 d) compared with normoxic control tumors (growth time from 70 to 500 microL, 15.6 d). Whereas RT delayed tumor growth regardless of the level of hypoxia, an additive beneficial therapeutic effect of tirapazamine to RT was observed only in hypoxic tumors (aGD, 12.9 d) but not in normoxic tumors (aGD, 6.0 d). This study provides compelling evidence that hypoxia imaging using (18)F-FAZA PET is able to predict the success of RCT of tumor-bearing mice using the hypoxia-activated chemotherapeutic agent tirapazamine. Pretreatment (18)F-FAZA PET, therefore, offers a way for the individualization of tumor treatment involving radiation. The data suggest that by reserving hypoxia-directed therapy to tumors with high (18)F-FAZA uptake, improvement of the therapeutic ratio is possible, as the therapeutic effect of tirapazamine seems to be restricted to hypoxic tumors.

Patterns of tumor oxygenation and their influence on the cellular hypoxic response and hypoxia-directed therapies

Deficiencies in the oxygenation of solid tumors are associated with poor patient prognosis due to changes in cell metabolism, angiogenesis, invasiveness and resistance to therapy. Work over the past 10 years has defined several distinct oxygen sensing pathways that together determine the cellular response to hypoxia. These include both a transcriptional response initiated by oxygen-dependent stabilisation of the HIF-1 transcription factor and an mRNA translational response characterized by activation of the unfolded protein response (UPR) and inhibition of mTOR signalling. Laboratory experiments have established the importance of these hypoxic response pathways for tumor growth and resistance to treatment. This has led to the development of agents aimed at targeting hypoxic response pathways in tumors, several of which are in clinical trials. However, several important features of the tumor microenvironment that may affect the success of these new therapies have not been thoroughly evaluated. Oxygenation patterns in human tumors have proven to be highly complex, leading to a large degree of heterogeneity with respect to the severity and duration of hypoxic exposure. Because both of these properties strongly influence the known cellular responses to hypoxia, this heterogeneity is expected to be a strong determinant of the fate of hypoxic cells and the success of new hypoxia-directed therapies. Here we summarize the important oxygen response pathways that currently serve as targets for therapy and their dependence on the specific oxygenation patterns that are expected in human tumors.

Hypoxia imaging-directed radiation treatment planning

Increasing evidence supports the role of the tumor microenvironment in modulating cancer behavior. Tissue hypoxia, an important and common condition affecting the tumor microenvironment, is well established as a resistance factor in radiotherapy. Increasing evidence points to the ability of hypoxia to induce the expression of gene products, which confer aggressive tumor behavior and promote broad resistance to therapy. These factors suggest that determining the presence or absence of tumor hypoxia is important in planning cancer therapy. Recent advances in PET hypoxia imaging, conformal radiotherapy, and imaging-directed radiotherapy treatment planning now make it possible to perform hypoxia-directed radiotherapy. We review the biological aspects of tumor hypoxia and PET imaging approaches for measuring tumor hypoxia, along with methods for conformal radiotherapy and image-guided treatment, all of which provide the underpinnings for hypoxia-directed therapy. As a case example, we review emerging data on PET imaging of hypoxia to direct radiotherapy.

Impact of Tumor Hypoxia and Anemia on Radiation Therapy Outcomes

Local recurrence remains a major obstacle to achieving cure of many locally advanced solid tumors treated with definitive radiation therapy. The microenvironment of solid tumors is hypoxic compared with normal tissue, and this hypoxia is associated with decreased radiosensitivity. Recent preclinical data also suggest that intratumoral hypoxia, particularly in conjunction with an acid microenvironment, may be directly or indirectly mutagenic. Investigations of the prognostic significance of the pretreatment oxygenation status of tumors in patients with head and neck or cervical cancer have demonstrated that increased hypoxia, typically designated in these studies as pO(2) levels below 2.5-10 mm Hg, is associated with decreased local tumor control and lower rates of disease-free and overall survival. Hypoxia-directed therapies in the radiation oncology setting include treatment using hyperbaric oxygen, fluosol infusion, carbogen breathing, and electron-affinic and hypoxic-cell sensitizers. These interventions have shown the potential to increase the effectiveness of curative-intent radiation therapy, demonstrating that the strategy of overcoming hypoxia may be a viable and important approach. Anemia is common in the cancer population and is suspected to contribute to intratumoral hypoxia. A review of the literature reveals that a low hemoglobin level before or during radiation therapy is an important risk factor for poor locoregional disease control and survival, implying that a strong correlation could exist between anemia and hypoxia (ultimately predicting for a poor outcome). While having a low hemoglobin level has been shown to be detrimental, it is unclear as to exactly what the threshold for "low" should be (studies in this area have used thresholds ranging from 9-14.5 g/dl). Optimal hemoglobin and pO(2) thresholds for improving outcomes may vary across and within tumor types, and this is an area that clearly requires further evaluation. Nonetheless, the correction of anemia may be a worthwhile strategy for radiation oncologists to improve local control and survival.