Changes In Tumor Growth Rate Research Articles

Tumor Growth Rate as a Validated Early Radiological Biomarker Able to Reflect Treatment-Induced Changes in Neuroendocrine Tumors: The GREPONET-2 Study.

Tumor growth rate (TGR) represents the percentage change in tumor volume per month (%/m). Previous results from the GREPONET study showed that TGR measured after 3 months (TGR3m) of starting systemic treatment (ST) or watch and wait (WW) was an early biomarker predicting progression-free survival (PFS) in neuroendocrine tumors (NET). Patients from 7 centers with advanced grade (G) 1/2 NETs from the pancreas (P)/small bowel (SB) initiating ST/WW were eligible. Computed tomography (CT)/MRI performed at prebaseline, baseline, and 3(±1) months of study entry were retrospectively reviewed. Aim-1: explore treatment-induced changes in TGR (ΔTGR3m-BL; paired T test), and Aim-2: validate TGR3m (<0.8%/m vs. ≥0.8%/m) as an early biomarker in an independent cohort (Kaplan-Meier/Cox regression). Of 785 patients screened, 127 were eligible. Mean (SD) TGR0 and TGR3m were 5.4%/m (14.9) and -1.4%/m (11.8), respectively. Mean (SD) ΔTGR3m-BL paired-difference was -6.8%/m (19.3; P < 0.001). Most marked ΔTGR3m-BL [mean (SD)] were identified with targeted therapies [-11.3%/m (4.7); P = 0.0237] and chemotherapy [-7.9%/m (3.4); P = 0.0261]. Multivariable analysis confirmed the absence of previous treatment (OR = 4.65; 95% CI, 1.31-16.52; P = 0.018) and low TGR3m (continuous variable; OR 1.09; 95% CI, 1.01-1.19; P = 0.042) to be independent predictors of radiologic objective response. When the multivariable survival analysis for PFS (Cox regression) was adjusted to grade (P = 0.004) and stage (P = 0.017), TGR3m ≥ 0.8 (vs. <0.8) maintained its significance as a prognostic factor (P < 0.001), whereas TGR0 and ΔTGR3m-BL did not. TGR3m ≥ 0.8%/m was confirmed as an independent prognostic factor for PFS [external validation; Aim-2; multivariable HR 2.21 (95% CI, 1.21-3.70; P = 0.003)]. TGR has a role as a biomarker for monitoring response to therapy for early identification of treatment-induced changes and for early prediction of PFS and radiologic objective response.

Abstract CN04-03: DNA vaccines as treatment for prostate cancer - understanding mechanisms of resistance

Abstract Anti-tumor vaccines have demonstrated clinical benefit in patients with advanced prostate cancer, and the first vaccine approved by FDA as a treatment for human cancer was a vaccine targeting the prostate tumor antigen prostatic acid phosphatase (PAP). Plasmid DNA, as another method of antigen delivery, offers significant potential safety and manufacturing advantages over other immunization approaches. DNA vaccines have been approved by USDA as treatments for diseases in fish, horses, dogs, and non-human primates. However, DNA vaccines have generally been perceived as less immunologically potent than other methods of antigen delivery in human clinical trials, leading to efforts to increase their immunogenicity. Most of these efforts have focused on increasing the delivery of vaccine to antigen-presenting cells using different carriers or by electroporation. Our group has evaluated repetitive immunization with plasmid DNA vaccines in rodent models, and has translated this approach to early clinical trials in men with low-volume recurrent prostate cancer with a DNA vaccine encoding PAP. We have demonstrated that persistent Th1-biased PAP-specific T-cell immune responses can be elicited in men with prostate cancer. Moreover, the development of persistent immunity appeared to be associated with favorable changes in tumor growth rate. A randomized phase II trial using this approach is currently ongoing in men with minimal residual prostate cancer to determine whether immunization can delay the time to metastatic disease progression (NCT01341652). In an effort to further improve the immunogenicity of DNA vaccines, we have explored methods to increase antigen presentation by encoding epitopes with increased MHC class I affinity or by increasing the duration of target antigen expression. While such “optimized” vaccines elicited increased numbers of antigen-specific CD8+ T cells, these T cells had less anti-tumor activity in vivo. We determined that immunization with plasmid DNA elicited antigen-specific IFNγ-secreting T cells that led to increased expression of PD-L1 on antigen-expressing tumor cells. However, immunization with the vaccine encoding high affinity epitopes resulted in antigen-specific CD8+ T cells with higher PD-1 expression. In the presence of PD-L1-expressing tumors these CD8+ were less effective. The anti-tumor activity was restored in the presence of PD-1 or PD-L1 blockade. Conversely, immunization with plasmid DNA engineered to increase the duration of antigen expression led to CD8+ T cells with normal PD-1 expression but higher LAG-3 expression. The anti-tumor activity was similarly restored in the presence of LAG-3 blockade. We are currently studying the mechanisms by which different T cell regulatory ligands are expressed following immunization. Notwithstanding, such findings suggest that subtle differences in the method of immunization can affect these different regulatory mechanisms, and hence the choice of optimal combination strategies may depend on identifying the specific mechanisms of resistance to immunization. In the case of patients immunized with a DNA vaccine encoding PAP, we have recently found that PD-L1 expression on circulating tumor (CD45-EpCAM+) cells was increased following immunization, analogous to our murine studies. In addition, PAP-specific secretion of IFNγ and granzyme B by T cells obtained from patients after immunization was increased in the presence of PD-1/PD-L1 blockade. Finally, using a trans vivo delayed type hypersensitivity (tvDTH) assay, we observed that PAP-specific immune responses in T cells obtained from patients after immunization with a DNA vaccine encoding PAP could be “uncovered” with PD-1 blockade but not blockade with anti-LAG-3 or anti-TIM-3. Collectively, these findings suggest that the PD-1/PD-L1 pathway and mechanism of resistance is most relevant to a DNA vaccine encoding PAP, and the efficacy of this vaccine might be augmented with PD-1 blockade. A clinical trial testing this approach in men with advanced prostate cancer, using this DNA vaccine and pembrolizumab, delivered either concurrently or sequentially, is currently underway (NCT02499835). Citation Format: Brian T. Rekoske, Viswa T. Colluru, Douglas G. McNeel. DNA vaccines as treatment for prostate cancer - understanding mechanisms of resistance. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr CN04-03.

RAGE expression in tumor-associated macrophages promotes angiogenesis in glioma.

Interaction of RAGE (the receptor for advanced glycation endproducts) with its ligands can promote tumor progression, invasion, and angiogenesis. Although blocking RAGE signaling has been proposed as a potential anticancer strategy, functional contributions of RAGE expression in the tumor microenvironment (TME) have not been investigated in detail. Here, we evaluated the effect of genetic depletion of RAGE in TME on the growth of gliomas. In both invasive and noninvasive glioma models, animal survival was prolonged in RAGE knockout (Ager(-/-)) mice. However, the improvement in survival in Ager(-/-) mice was not due to changes in tumor growth rate but rather to a reduction in tumor-associated inflammation. Furthermore, RAGE ablation in the TME abrogated angiogenesis by downregulating the expression of proangiogenic factors, which prevented normal vessel formation, thereby generating a leaky vasculature. These alterations were most prominent in noninvasive gliomas, in which the expression of VEGF and proinflammatory cytokines were also lower in tumor-associated macrophages (TAM) in Ager(-/-) mice. Interestingly, reconstitution of Ager(-/-) TAM with wild-type microglia or macrophages normalized tumor vascularity. Our results establish that RAGE signaling in glioma-associated microglia and TAM drives angiogenesis, underscoring the complex role of RAGE and its ligands in gliomagenesis.

IB-04 * EXPRESSION OF RAGE BY TUMOR MACROPHAGES PROMOTES ANGIOGENESIS IN GLIOMAS

Interaction of RAGE with its ligands can promote tumor progression, invasion and angiogenesis. Although blockage of RAGE signaling has been proposed as a potential anti-cancer therapy, the contribution of RAGE expression in tumor microenvironement (TME) to tumorigenesis has not been investigated in detail. Here, we evaluated the effect of genetic depletion of RAGE in TME on the growth of gliomas. In both invasive and non-invasive glioma models, animal survival was prolonged in Rage−/- mice. This improvement in animal survival, however, was not due to changes in tumor growth rate, but a reduction in tumor-associated inflammation in Rage−/- mice. Furthermore, RAGE ablation in TME abrogated angiogenesis by downregulating the expression of pro-angiogenic factors which prevented vessel pruning, and resulted in the generation of leaky vasculature. These alterations, however, were most prominent in non-invasive gliomas where the expression of VEGF and pro-inflammatory cytokines were also lower in Rage−/- tumor-associated macrophages. Interestingly, reconstituting Rage−/- tumor macrophages with either wild-type microglia or macrophages normalized tumor vascularity. This is the first report to demonstrate the pro-angiogenic function of RAGE signaling in tumor macrophages and underscores the complex role of RAGE and its ligands in gliomagenesis.

Integrin αvβ6 Promotes an Osteolytic Program in Cancer Cells by Upregulating MMP2

The molecular circuitries controlling osseous prostate metastasis are known to depend on the activity of multiple pathways, including integrin signaling. Here, we demonstrate that the αvβ6 integrin is upregulated in human prostate cancer bone metastasis. In prostate cancer cells, this integrin is a functionally active receptor for fibronectin and latency-associated peptide-TGF-β1; it mediates attachment and migration upon ligand binding and is localized in focal contacts. Given the propensity of prostate cancer cells to form bone metastatic lesions, we investigated whether the αvβ6 integrin promotes this type of metastasis. We show for the first time that αvβ6 selectively induces matrix metalloproteinase 2 (MMP2) in vitro in multiple prostate cancer cells and promotes osteolysis in vivo in an immunodeficient mouse model of bone metastasis through upregulation of MMP2, but not MMP9. The effect of αvβ6 on MMP2 expression and activity is independent of androgen receptor in the analyzed prostate cancer cells. Increased levels of parathyroid hormone-related protein (PTHrP), known to induce osteoclastogenesis, were also observed in αvβ6-expressing cells. However, by using MMP2 short hairpin RNA, we demonstrate that the αvβ6 effect on bone loss is due to upregulation of soluble MMP2 by the cancer cells, not due to changes in tumor growth rate. Another related αv-containing integrin, αvβ5, fails to show similar responses, underscoring the significance of αvβ6 activity. Overall, these mechanistic studies establish that expression of a single integrin, αvβ6, contributes to the cancer cell-mediated program of osteolysis by inducing matrix degradation through MMP2. Our results open new prospects for molecular therapy for metastatic bone disease.

The Effect of Intravenous Immunoglobulin (IVIG) on Fibrosarcoma Growth in CBA and C57BL/6 Mice

Background: The effect of IVIG in cancer treatment is likely to be mediated by immune cells that regulate tumor progression. Here we studied the effect of IVIG on tumor development in two immunologically contrasting mouse strains, CBA and C57BL/6. We compared the rate of tumor growth, the number of circulating neutrophils and oxidative characteristics of tumor tissue in IVIG-treated and control mice. Results: The animals were inoculated with fibrosarcoma S37 cells, and 14 days after inoculation there was a significant difference between IVIG-treated and control mice: IVIG treatment inhibited tumor growth in CBA mice and stimulated it in C57BL/6. The changes in tumor growth rate were associated with biochemical alterations in tumor tissue. According to the data of biochemical tests, IVIG-treatment influenced activity of tissue myeloperoxidase (neutrophil azurophilic granule enzyme) in CBA and C57BL/6 and of some antioxidant enzymes (glutathione-S-transferase, catalase, glutathione peroxidase) in C57BL/6 mice. Neutrophils content was increased in IVIG-treated CBA mice while in C57BL/6 it remained unaltered and significantly lower than in CBA as was shown by direct count on smears. Conclusions: These results suggest the tight link between the effects of IVIG upon neutrophils and tumor tissue redox balance as a part of regulatory mechanism of tumor growth.

A phase II study of a yeast-based therapeutic cancer vaccine, GI-6207, targeting CEA in patients with minimally symptomatic, metastatic medullary thyroid cancer.

TPS3127 Background: Saccharomyces cerevisiae has been genetically modified to express CEA protein and developed under a CRADA with GlobeImmune/NCI as a heat-killed immune-stimulating, therapeutic cancer vaccine (GI-6207). A phase I study with GI-6207 demonstrated safety, biomarker stabilization and enhanced immune response in some patients. CEA is over-expressed in multiple malignancies, including medullary thyroid cancer (MTC). Two therapies recently approved by the FDA for metastatic MTC (vandetanib, cabozantinib) come with toxicity and should be reserved for symptomatic/progressive disease. However, a large population of asymptomatic MTC patients has small tumor burden and/or disease that is more indolent. The standard management of these patients is observation. Preliminary data suggest that tumor growth measured by the rate of CEA and calcitonin increase can be quantified in a 3-6 months. Retrospective data from prostate cancer studies suggest vaccines can alter growth rates within 3-4 months. We hypothesize that GI-6207 can alter tumor growth rates in MTC and impact long-term outcome. Methods: A phase II study will evaluate the effect of GI-6207 onthe rates ofincrease in calcitonin in metastatic MTC. 34 patients with minimally symptomatic, radiographically evaluable, metastatic MTC will be randomized 1:1. Arm A will receive vaccine for a year from the time of enrollment. Arm B will receive vaccine after 6 months of surveillance. GI-6207 will be administered subcutaneously at 4 sites (10 yeast units/site), every 2 weeks for 3 months, then monthly up to 1 year. The primary endpoint will compare the effect of GI-6207 on calcitonin kinetics between the vaccine and surveillance arms in the first 6 months. Secondary endpoints include immunologic responses (including antigen-specific T cell responses), objective responses, time to progression, and changes in CEA kinetics. If this trial can prospectively demonstrate that vaccines can alter tumor growth rates, and if such changes are associated with clinical outcomes, then changes in tumor growth rates may become a clinical metric to evaluate vaccine efficacy in MTC and other populations.

Preclinical pharmacokinetic/pharmacodynamic models to predict synergistic effects of co-administered anti-cancer agents

Pharmacokinetic/pharmacodynamic (PK/PD) models have been shown to be useful in predicting tumor growth rates in mouse xenografts. We applied novel PK/PD models to the published anticancer combination therapies of tumor growth inhibition to simulate synergistic changes in tumor growth rates. The parameters from the PK/PD model were further used to estimate clinical doses of the combination. A PK/PD model was built that linked the dosing regimen of a compound to the inhibition of tumor growth in mouse xenograft models. Two subsequent PK/PD models were developed to simulate the published tumor growth profiles of combination treatments. Model I predicts the tumor growth curve assuming that the effect of two anticancer drugs, AZD7762 and irinotecan, is synergistic when given in combination. Model II predicts the tumor growth curve assuming that the effect of co-administering flavopiridol and irinotecan is maximally synergistic when dosed at an optimal interval. Model I was able to account for the synergistic effects of AZD7762 following the administration of irinotecan. When Model II was applied to the antitumor activity of irinotecan and flavopiridol combination therapy, the modeling was able to reproduce the optimal dosing interval between administrations of the compounds. Furthermore, Model II was able to estimate the biologically active dose of flavopiridol recommended for phase II studies. The timing of clinical combination therapy doses is often selected empirically. PK/PD models provide a theoretical structure useful in the design of the optimal clinical dose, frequency of administration and the optimal timing of administration between anticancer agents to maximize tumor suppression.

Hypersensitivity and Loss of Disease Site Targeting Caused by Antibody Responses to PEGylated Liposomes

The systemic application of nucleic acid drugs requires delivery systems that overcome the poor pharmacokinetics, limited biodistribution, and inefficient uptake of nucleic acids. PEGylated liposomes show considerable promise because of their intrinsic ability to accumulate at disease sites and facilitate transfection of target cells. Unlike many viral vectors, PEGylated liposomes are generally considered to be nonimmunogenic. We have developed a PEGylated liposome for the systemic administration of plasmid DNA that achieves high levels of selective gene expression at distal tumor sites. Here we report that the in vivo efficacy and safety of these systems can be severely compromised following repeat administration. This phenomenon is characterized by a loss of disease site targeting, accelerated clearance from the blood, and acute hypersensitivity. These effects are fully attributable to a surprisingly robust, long-lived antibody response generated against polyethylene glycol (PEG) that results from the strong adjuvant effect of the plasmid payload. Importantly, immunogenicity may be substantially reduced by modifying the alkyl chain of the PEG-lipid conjugate, thereby allowing successful repeat dosing of the modified plasmid formulations without adverse side effects. Immunogenicity is a relevant concern for a number of nonviral delivery systems given the potent immunostimulatory properties of many nucleic acid drugs.

Effect of chronic fish oil supplementation on renal function of normal and cachectic rats.

In the present study we determined the effect of chronic diet supplementation with n-3 PUFA on renal function of healthy and cachectic subjects by providing fish oil (1 g/kg body weight) to female rats throughout pregnancy and lactation and then to their offspring post-weaning and examined its effect on renal function parameters during their adulthood. The animals were divided into four groups of 5-10 rats in each group: control, control supplemented with fish oil (P), cachectic Walker 256 tumor-bearing (W), and W supplemented with fish oil (WP). Food intake was significantly lower in the W group compared to control (12.66 +/- 4.24 vs 25.30 +/- 1.07 g/day). Treatment with fish oil significantly reversed this reduction (22.70 +/- 2.94 g/day). Tumor growth rate was markedly reduced in the P group (16.41 +/- 2.09 for WP vs 24.06 +/- 2.64 g for W). WP group showed a significant increase in mean glomerular filtration rate compared to P and control (1.520 +/- 0.214 ml min-1 kg body weight-1; P < 0.05). Tumor-bearing groups had low urine osmolality compared to control rats. The fractional sodium excretion decreased in the W group compared to control (0.43 +/- 0.16 vs 2.99 +/- 0.87%; P < 0.05), and partially recovered in the WP group (0.90 +/- 0.20%). In summary, the chronic supplementation with fish oil used in this study increased the amount of fat in the diet by only 0.1%, but caused remarkable changes in tumor growth rate and cachexia, also showing a renoprotective function.

Combining doxorubicin and liposomal anti-HER-2/NEU antisense oligodeoxynucleotides to treat HER-2/NEU-expressing MDA-MB-435 breast tumor model.

This study assessed the in vivo therapeutic activity of an antisense molecule targeted against HER-2/neu expressing mRNA. Antisense activity was evaluated in female SCID/Rag2m mice bearing subcutaneous tumors derived from HER-2/neu-transfected MDA-MB-435 (MDA-MB-435(HER2)) cells, a transfected line derived from the human breast cancer MDA-MB-435 cell line. Animals were treated with free or liposome-encapsulated antisense. The area under the curve (AUC(0-24h)) of the liposomal formulated antisense was demonstrated to be more than 30-fold greater than that of free antisense following intravenous administration. Efficacy was determined by assessing changes in tumor growth rate as well as by an immunohistological end-point evaluating HER-2/neu expression. HER-2/neu protein expression was reduced in mice bearing HER-2/neu-transfected MDA-MB-435 tumors when treated with liposomal antisense. However, tumors in these mice grew at a faster rate than the control, a result that was interpreted to be a consequence of selection of a more rapidly proliferating HER-2/neu-negative subpopulation of cells. Effective control of the MDA-MB-435(HER2) tumors was achieved when antisense treatment was combined with doxorubicin. Tumors derived from animals treated with the combination of doxorubicin and the liposomal antisense against HER-2/neu exhibited no detectable levels of HER-2/neu expression. Antisense targeted against HER-2/neu mRNA was effective in reducing or eliminating HER-2/neu protein expression, and when combined wtih doxorubicin treatment was efficacious in the treatment of mice bearing HER-2/neu-overexpressing human xenograft tumors.

Development and validation of a cellular transplant model for leukemia in fischer rats: A short-term assay for potential anti-leukemic chemicals

The efficacy of a leukemia cell transplant model to measure potential chemotherapeutic activity was tested with five different chemicals that had previously been evaluated in 2-year studies. Leukemic spleen cells from Fischer rats were injected subcutaneously into syngeneic recipients and the effects of chemical treatment on tumor progression were evaluated at 70 days post-transplant. The data from the short-term assay were in all cases correlated with the trends reported for mononuclear cell leukemia in 2-year studies, where two chemicals were reported to decrease the incidence and three chemicals were reported to increase the incidence of leukemia. Short-term treatment with the two chemicals which caused negative trends for leukemia (2-ethoxyethanol or ethylene glycol monoethyl ether; 4-hexylresorcinol) delayed and/or reduced tumor growth in the transplant model in a dose-related fashion, as exhibited by reduction or elimination of splenomegaly and leukoblastosis, and a reversal in the depression of red blood cell indices or platelet counts. By contrast, the rate of tumor progression was increased in the short-term assay of the three chemicals which previously caused increased trends for leukemia in 2-year studies (pyridine; 2,4,6-trichlorophenol, dichlorvos). The severity of the mononuclear cell leukemia in the transplant recipients, as measured by histopathological examination of spleen and liver, was correlated with the changes in tumor growth rates. The in vivo leukemia transplant model is a short-term assay that could be used to screen a variety of potential chemotherapeutic agents, or to study structure-activity relationships within one class of chemicals.

Solid tumor models for the assessment of different treatment modalities: I. Radiation-induced changes in growth rate characteristics of a solid tumor model.

A computer program has been developed to quantitatively evaluate changes in tumor growth rates of a solid tumor model (hepatoma 3924A) after a series of radiation doses from 375 R to 3750 R. The computer-derived growth curves are simulated from the volumes of the individual tumors rather than from the mean tumor volume at any specific time point after treatment. The ability to generate data from a family of tumor growth curves permits a more precise evaluation of therapeutic effects on tumors than can be obtained with conventional methods. The quantitative determination of equivalent amounts of radiation needed to produce comparable 5-fluorouracil-induced changes in tumor growth rate has been made. The ability to determine quantitatively radiotherapeutic and chemotherapy equivalents on these solid tumor models has direct implications in regard to our effort to improve the treatment of cancer. At present no specific solid tumor or groups of solid tumors have provided all of the necessary information for clinical utilization in therapeutic scheduling of different forms of cancer treatment. Since solid tumors comprise the majority of human cancer, one of the primary objectives of these studies has been the establishment of a solid tumor model that could serve both as a system for devising improved therapeutic scheduling and for a better understanding of solid tumors.