Heterogeneity in primary tumors and corresponding metastases: could it provide us with any hints to personalize cancer therapy?

Impact of quantization algorithm and number of gray level intensities on variability and repeatability of low field strength magnetic resonance image-based radiomics texture features

PURPOSE

The purpose of this work was to investigate the impact of quantization preprocessing parameter selection on variability and repeatability of texture features derived from low field strength magnetic resonance (MR) images.

METHODS

Texture features were extracted from low field strength images of a daily image QA phantom with four texture inserts. Feature variability over time was quantified using all combinations of three quantization algorithms and four different numbers of gray level intensities. In addition, texture features were extracted using the same combinations from the low field strength MR images of the gross tumor volume (GTV) and left kidney of patients with repeated set up scans. The impact of region of interest (ROI) preprocessing on repeatability was investigated with a test-retest study design.

RESULTS

The phantom ROIs quantized to 64 Gy level intensities using the histogram equalization method resulted in the greatest number of features with the least variability. There was no clear method that resulted in the highest repeatability in the GTV or left kidney. However, eight texture features extracted from the GTV were repeatable regardless of ROI processing combination.

CONCLUSION

Low field strength MR images can provide a stable basis for texture analysis with ROIs quantized to 64 Gy levels using histogram equalization, but there is no clear optimal combination for repeatability.

Detecting Immune Response to Therapies Targeting PDL1 and BRAF by Using Ferumoxytol MRI and Macrin in Anaplastic Thyroid Cancer

Background Anaplastic thyroid cancer (ATC) is aggressive with a poor prognosis, partly because of the immunosuppressive microenvironment created by tumor-associated macrophages (TAMs). Purpose To understand the relationship between TAM infiltration, tumor vascularization, and corresponding drug delivery by using ferumoxytol-enhanced MRI and macrin in an ATC mouse model. Materials and Methods ATC tumors were generated in 6-8-week-old female B6129SF1/J mice through intrathyroid injection to model orthotopic tumors, or intravenously to model hematogenous metastasis, and prospectively enrolled randomly into treatment cohorts (n = 94 total; August 1, 2018, to January 15, 2020). Mice were treated with vehicle or combined serine/threonine-protein kinase B-Raf (BRAF) kinase inhibitor (BRAFi) and anti-PDL1 antibody (aPDL1). A subset was cotreated with therapies, including an approximately 70-nm model drug delivery nanoparticle (DDNP) to target TAM, and an antibody-neutralizing colony stimulating factor 1 receptor (CSF1R). Imaging was performed at the macroscopic level with ferumoxytol-MRI and microscopically with macrin. Genetically engineered Braf^V600E/WT p53-null allografts were used and complemented by a GFP-transgenic derivative and human xenografts. Tumor-bearing organs were processed by using tissue clearing and imaged with confocal microscopy and MRI. Two-tailed Wilcoxon tests were used for comparison (≥five per group). Results TAM levels were higher in orthotopic thyroid tumors compared with pulmonary metastatic lesions by 79% ± 23 (standard deviation; P < .001). These findings were concordant with ferumoxytol MRI, which showed 136% ± 88 higher uptake in thyroid lesions (P = .02) compared with lung lesions. BRAFi and aPDL1 combination therapy resulted in higher tumor DDNP delivery by 39% ± 14 in pulmonary lesions (P = .004). Compared with the untreated group, tumors following BRAFi, aPDL1, and CSF1R-blocking antibody combination therapy did not show greater levels of TAM or DDNP (P = .82). Conclusion In a mouse model of anaplastic thyroid cancer, ferumoxytol MRI showed 136% ± 88 greater uptake in orthotopic thyroid tumors compared with pulmonary lesions, which reflected high vascularization and greater tumor-associated macrophage (TAM) levels. Serine/threonine-protein kinase B-Raf inhibitor and anti-programmed death ligand 1 antibody elicited higher local TAM levels and 43% ± 20 greater therapeutic nanoparticle delivery but not higher vascularization in pulmonary tumors. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Luker in this issue.

Hotspot oncomutations: implications for personalized cancer treatment

Understanding the extent to which specific tumor mutations impact or mediate patient response to particular cancer therapies has become a rapidly increasing area of research. Recent research findings regarding four predominant mutational targets (KRAS, BRAF, EGFR and PIK3CA) show that these tumor mutations have predictive power for identifying which patients are likely to respond to particular therapies, and have prognostic significance irrespective of treatment. However, in this regard, the literature is frequently nuanced and sometimes contradictory. This lack of clarity may be due, at least in part, to the utilization of mutation detection methods with varying sensitivities across studies of different patient populations. Nevertheless, considerable evidence suggests minor tumor subpopulations may be contributing to inappropriate patient stratification, development of resistance to treatment, and the relapse that often follows treatment with molecularly targeted therapies. Consequently, mutant tumor subpopulations need to be considered in order to improve strategies for personalized cancer treatment.

Heterogeneity between primary colon carcinoma and paired lymphatic and hepatic metastases

Heterogeneity is one of the recognized characteristics of human tumors, and occurs on multiple levels in a wide range of tumors. A number of studies have focused on the heterogeneity found in primary tumors and related metastases with the consideration that the evaluation of metastatic rather than primary sites could be of clinical relevance. Numerous studies have demonstrated particularly high rates of heterogeneity between primary colorectal tumors and their paired lymphatic and hepatic metastases. It has also been proposed that the heterogeneity between primary colon carcinomas and their paired lymphatic and hepatic metastases may result in different responses to anticancer therapies. The heterogeneity in primary colon carcinoma and corresponding metastases by genome‑wide gene expression analysis has not been extensively studied. In the present study, we investigated the differentially expressed genes between a primary colon carcinoma specimen (obtained from a 40-year-old female colon carcinoma patient with lymphatic and hepatic metastases) and its paired lymphatic and hepatic metastases by genome-wide gene expression analysis using GeneChip HGU133Plus2.0 expression arrays. Our results demonstrate that genome-wide gene expression varies between primary colon carcinoma and its paired lymphatic and hepatic metastases.

Differential response to EGFR- and VEGF-targeted therapies in patient-derived tumor tissue xenograft models of colon carcinoma and related metastases

Heterogeneity in primary tumors and related metastases may result in failure of antitumor therapies, particularly in targeted therapies for the treatment of cancer. In this study, patient-derived tumor tissue (PDTT) xenograft models of colon carcinoma with lymphatic and hepatic metastases were used to evaluate the response to EGFR- and VEGF-targeted therapies. Our results showed that primary colon carcinoma and its corresponding lymphatic and hepatic metastases have a different response rate to anti-EGFR (cetuximab) and anti-VEGF (bevacizumab) therapies. However, the underlying mechanism of these types of phenomenon is still unclear. To investigate whether such phenomena may result from the heterogeneity in primary colon carcinoma and related metastases, we compared the expression levels of cell signaling pathway proteins using immunohistochemical staining and western blotting, and the gene status of KRAS using pyrosequencing in the same primary colon carcinoma and its corresponding lymphatic and hepatic metastatic tissues which were used for establishing the PDTT xenograft models. Our results showed that the expression levels of EGFR, VEGF, Akt/pAkt, ERK/pERK, MAPK/pMAPK, and mTOR/pmTOR were different in primary colon carcinoma and matched lymphatic and hepatic metastases although the KRAS gene status in all cases was wild-type. Our results indicate that the heterogeneity in primary colon carcinoma and its corresponding lymphatic and hepatic metastases may result in differences in the response to dual-inhibition of EGFR and VEGF.

Antitumor effect of FP3 in a patient-derived tumor tissue xenograft model of gastric carcinoma through an antiangiogenic mechanism

FP3 (KH902/KH903) is a novel vascular endothelial growth factor (VEGF) blocker with antiangiogenic properties. Previous studies revealed that FP3, a humanized fusion protein that combines ligand binding elements from the extracellular domains of VEGF receptors 1 and 2 and the Fc portion of IgG1, has an inhibitory effect on the VEGF-mediated proliferation and migration of human umbilical vein endothelial cells, and VEGF-mediated vessel sprouting of rat aortic rings in vitro. Thus, FP3 was considered as a new promising agent in treating human choroidal neovascularization (CNV) caused by age-related macular degeneration (AMD). FP3 also has an antitumor effect in a non-small cell lung cancer cell line (A549) xenograft model in nude mice. However, little is known of the direct effects of FP3 on tumor vessels. In this study, we investigated the effects of FP3 on blood vessels in a patient-derived tumor tissue (PDTT) xenograft model of gastric carcinoma, using large tumors with established vasculature. Treatment with FP3 caused robust and early changes in endothelial cells and pericytes of vessels in the PDTT xenograft model. Vascular density decreased and vascular sprouting was suppressed by treatment with FP3. Pericytes did not degenerate to the same extent as endothelial cells, and those on surviving tumor vessels achieved a more normal phenotype. Our results revealed that FP3 has a direct and rapid antiangiogenic effect on tumor vessels, which was achieved mainly via regression of tumor vasculature, inhibition of new and recurrent vessel growth, and normalization of existing tumor vasculature.

Assessment of a novel VEGF targeted agent using patient-derived tumor tissue xenograft models of colon carcinoma with lymphatic and hepatic metastases

The lack of appropriate tumor models of primary tumors and corresponding metastases that can reliably predict for response to anticancer agents remains a major deficiency in the clinical practice of cancer therapy. It was the aim of our study to establish patient-derived tumor tissue (PDTT) xenograft models of colon carcinoma with lymphatic and hepatic metastases useful for testing of novel molecularly targeted agents. PDTT of primary colon carcinoma, lymphatic and hepatic metastases were used to create xenograft models. Hematoxylin and eosin staining, immunohistochemical staining, genome-wide gene expression analysis, pyrosequencing, qRT-PCR, and western blotting were used to determine the biological stability of the xenografts during serial transplantation compared with the original tumor tissues. Early passages of the PDTT xenograft models of primary colon carcinoma, lymphatic and hepatic metastases revealed a high degree of similarity with the original clinical tumor samples with regard to histology, immunohistochemistry, genes expression, and mutation status as well as mRNA expression. After we have ascertained that these xenografts models retained similar histopathological features and molecular signatures as the original tumors, drug sensitivities of the xenografts to a novel VEGF targeted agent, FP3 was evaluated. In this study, PDTT xenograft models of colon carcinoma with lymphatic and hepatic metastasis have been successfully established. They provide appropriate models for testing of novel molecularly targeted agents.