Osamu Maenishi

Activation of ERBB2 Signaling Causes Resistance to the EGFR-Directed Therapeutic Antibody Cetuximab

Several cancers become resistant to cetuximab by activating a bypass signaling pathway and preventing cetuximab inhibition of ERK1/2-stimulated growth. Combating Resistance to an EGF Receptor Inhibitor Many promising anticancer drugs are effective only for a limited time, because the tumor cells develop resistance. Cetuximab, directed against the epidermal growth factor receptor (EGFR), is no exception, and patients with colorectal, head and neck, or non–small cell lung cancer eventually cease to respond to the drug. Yonesaka and colleagues have determined that cetuximab-resistant cancer cells—both in culture and in patients—can up-regulate signaling through the ERBB2 growth factor receptor in several ways, permanently turning on extracellular signal–regulated kinase 1/2 (ERK1/2)–mediated growth, differentiation, and survival. They further show that interference with the ERBB2 pathway restores the ability of cetuximab to control these cancers, pointing to a promising resistance-fighting approach. The authors generated clones of cetuximab-resistant non–small cell lung and colorectal cancer cell lines by exposing the cells to increasing concentration of the drug. In some of these resistant clones, the ERBB2 receptor oncogene was genetically amplified, resulting in activated ERK1/2 signaling. Down-regulation of ERBB2 with a small interfering RNA or antibody restored sensitivity. Other clones did not have amplified ERBB2 genes but did make excess heregulin, an activating ligand for the ERBB2 receptor. Heregulin depletion or ERBB2 inhibition restored cetuximab sensitivity. After replicating these studies in xenografts in mice, the authors also looked for evidence that these resistance-associated alterations pertain to human tumors. In several groups of patients with colorectal cancer, they saw decreased survival or decreased sensitivity to cetuximab in those who exhibited amplified ERBB2 gene or higher heregulin concentrations. The concordance of their cellular data with patient experience improves confidence that concomitant treatment of certain lung, head and neck, or colorectal cancers with cetuximab and an anti-ERBB2 drug may prevent or delay the development of drug resistance. These studies add to other successes for this approach, which has also been used for analysis of other molecular targeted therapies, including EGFR kinase inhibitors. Cetuximab, an antibody directed against the epidermal growth factor receptor, is an effective clinical therapy for patients with colorectal, head and neck, and non–small cell lung cancer, particularly for those with KRAS and BRAF wild-type cancers. Treatment in all patients is limited eventually by the development of acquired resistance, but little is known about the underlying mechanism. Here, we show that activation of ERBB2 signaling in cell lines, either through ERBB2 amplification or through heregulin up-regulation, leads to persistent extracellular signal–regulated kinase 1/2 signaling and consequently to cetuximab resistance. Inhibition of ERBB2 or disruption of ERBB2/ERBB3 heterodimerization restores cetuximab sensitivity in vitro and in vivo. A subset of colorectal cancer patients who exhibit either de novo or acquired resistance to cetuximab-based therapy has ERBB2 amplification or high levels of circulating heregulin. Collectively, these findings identify two distinct resistance mechanisms, both of which promote aberrant ERBB2 signaling, that mediate cetuximab resistance. Moreover, these results suggest that ERBB2 inhibitors, in combination with cetuximab, represent a rational therapeutic strategy that should be assessed in patients with cetuximab-resistant cancers.

Identification and characterization of IgG4‐associated autoimmune hepatitis

Background: Autoimmune hepatitis (AIH) and autoimmune pancreatitis (AIP) share clinical and pathological features such as high serum levels of immunoglobulin (Ig) G and autoantibodies, and lymphoplasmacytic infiltration, suggesting the presence of common immunological abnormalities. However, little is known about the possible involvement of IgG4, a hallmark of AIP, in AIH.

Differential diagnosis of nodular lesions in cirrhotic liver by post-vascular phase contrast-enhanced US with Levovist: comparison with superparamagnetic iron oxide magnetic resonance images

BackgroundWe investigated the diagnostic utility of post-vascular phase contrast-enhanced ultrasonography (US) and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance imaging (MRI) as compared to the histological diagnosis of differential grades of hepatocellular carcinomas (HCCs).MethodsForty-nine patients with histologically characterized liver nodules (well-differentiated HCC, n = 20; moderately differentiated HCC, n = 19; poorly differentiated HCC, n = 1; dysplastic nodule, n = 9) received contrast-enhanced US and SPIO-MRI. Subsequently, we quantitatively evaluated the relationships between the images of the nodules and their histological diagnosis and differential grades.ResultsThe ratio of the echogenicity of the tumorous area to that of the nontumorous area with post-vascular phase contrast-enhanced US (post-vascular phase ratio) decreased as nodules became less differentiated (P < 0.05; Kruskal-Wallis test). The ratio of the intensity of the nontumorous area to that of the tumorous area on SPIO-enhanced MR images (SPIO intensity index) also decreased as nodules became less differentiated (P < 0.01). The post-vascular phase ratio correlated with the SPIO intensity index for HCCs and dysplastic nodules (r = 0.76). The conformity of the result from the post-vascular phase contrast-enhanced US and SPIO-MRI was 96%.ConclusionsContrast-enhanced US is a valuable method for predicting the histological grade of HCCs in cirrhotic patients, and may be a good alternative to SPIO-enhanced MRI.

Value of Liver Parenchymal Phase Contrast-Enhanced Sonography to Diagnose Premalignant and Borderline Lesions and Overt Hepatocellular Carcinoma

OBJECTIVE The objective of our study was to investigate whether liver parenchymal phase contrast-enhanced sonography can provide additional information for assessing histologic grades of hepatocellular carcinoma (HCC). SUBJECTS AND METHODS Contrast-enhanced sonography using Levovist of 50 hepatic nodules was performed. The vascular and liver parenchymal perfusion patterns were evaluated. The sensitivity, specificity, and accuracy of the histologic diagnosis of the tumors using vascular phase imaging only and systematically combined vascular phase imaging with liver parenchymal phase imaging were calculated. We also performed histologic examination and immunostaining for the detection of Kupffer cells and calculated the Kupffer cell count in the tumorous tissue relative to that in the nontumorous tissue (Kupffer cell ratio) and quantitatively evaluated the relationship between the Kupffer cell ratio and the perfusion patterns seen on liver parenchymal phase imaging. RESULTS The specificity and accuracy of contrast-enhanced sonography in the diagnosis of dysplastic nodules and of moderately and poorly differentiated HCCs were improved by adding liver parenchymal phase imaging (dysplastic nodules, 74% and 78% vs 83% and 86%, respectively; moderately and poorly differentiated HCCs, 74% and 86% vs 85% and 92%). The diagnostic accuracy of contrast-enhanced sonography for dysplastic nodules showed a trend of improvement with the addition of liver parenchymal phase imaging (p = 0.07). Kupffer cell ratios for tumors that showed hypoperfusion during the liver parenchymal phase were significantly lower than those for tumors showing isoperfusion (p < 0.05). CONCLUSION Adding liver parenchymal phase imaging to contrast-enhanced sonography protocols may yield additional information that can be used to assess histologic grades of tumor and that leads to an improvement in the differential diagnosis of nodular lesions associated with the cirrhotic liver. Further case studies are required in larger numbers of patients for a longer follow-up period.

Erythropoietin/Erythropoietin-receptor system as an angiogenic factor in chemically induced murine hepatic tumors

BackgroundTo clarify the role of erythropoietin (Epo) in hepatic tumor angiogenesis, expression of Epo and its receptor (Epo-R) and content of Epo were investigated in murine chemically induced hepatic tumors.MethodsTo induce hepatic tumors and cirrhosis, diaminobenzidine was administered to Wistar rats for 5 months. In total, 30 hepatic tumors of greater than 3 mm in diameter were induced in 12 rats. The 30 hepatic tumors were resected with the surrounding hepatic tissues. The Epo content was measured by a radioimmunoassay (RIA) method. The number of tumor vessels in a definite area was counted in 100 areas of each tumor. To demonstrate the expression of Epo-R in tumors or surrounding liver tissues, immunohistochemial staining for Epo-R was performed.ResultsThe Epo content of tumors ranged from 6.1 to 97.8 mU/ml, with a median of 21.8 mU/ml, which was significantly higher than that of the cirrhotic tissues adjacent to the tumors. Epo was not detectable in the normal or cirrhotic liver tissues without tumors. A significant correlation between Epo content and vascular density was noted in the 30 hepatic tumors (correlation coefficient, 0.480; P = 0.01). Immunoreactive Epo-R was detectable in the endothelium of intervening vessels of all hepatic tumors examined.ConclusionThe Epo/Epo-R system is related to the angiogenesis of murine hepatic tumors.

Unique histological characteristics of Scedosporium that could aid in its identification.

Scedosporium prolificans has been increasingly recognized as an etiological agent of disseminated mycelial infections in profoundly immunocompromised patients. Reported herein is a case of disseminated S. prolificans infection in a patient undergoing anti‐neoplastic chemotherapy for acute myeloid leukemia. Antemortem blood culture yielded S. prolificans, which was confirmed on conventional morphological examination and polymerase chain reaction‐based DNA sequencing targeting internally transcribed spacer regions. Histopathology of autopsy specimens indicated fungal infection in the heart, lungs, liver, kidneys, spleen, pancreas and gastrointestinal tract, with the development of hemorrhagic and ischemic necrosis. The infecting fungus had developing septate hyphae and was identified as belonging to the genus Scedosporium, on in situ hybridization of tissue. The combination of haphazardly branching hyphae and lemon‐shaped conidia appeared to be the most useful distinguishing features to allow differentiation of this fungus from other filamentous fungi in tissue. Three other unique histopathological characteristics of the fungus were noted: (i) parallel hyphae bridged at right angles to produce letter‐H patterns; (ii) intravascular conidiation; and (iii) purple conidia in tissue, though these are usually described as brown in most text books. Precise histopathology, in addition to other techniques such as in situ hybridization, can aid in the identification of etiological fungi.

HER2 genomic amplification in circulating tumor DNA from patients with cetuximab-resistant colorectal cancer

Background Patients with metastatic colorectal cancer (mCRC) harboring wild-type KRAS benefit from epidermal growth factor receptor (EGFR)-targeted therapy. However, patients who are treated with anti-EGFR antibodies will eventually develop the resistance to those agents. HER2 amplification is one of the mechanisms conferring resistance to anti-EGFR antibody therapy and could therefore be a potential therapeutic target. The aim of this study was to detect HER2 amplification in circulating tumor DNA (ctDNA) from patients with CRC and acquired resistance to anti-EGFR antibody therapy. Results Our data showed that 22% (4/18) of patients in the cohort exhibited HER2 amplification. One of these patients was found to be positive for HER2 amplification in matched tumor specimens collected after cetuximab therapy, at which point the patient had acquired cetuximab resistance, despite being negative for HER2 amplification prior to therapy. Methods We analyzed plasma ctDNA using digital polymerase chain reaction (PCR) from 18 patients with CRC, who had been treated with anti-EGFR antibody-based therapy (cetuximab) and subsequently acquired resistant cetuximab. HER2 gene copy number was analyzed using fluorescence in situ hybridization in tumor samples before and after acquisition of resistance to cetuximab-based therapy. Conclusion Analysis of plasma ctDNA by digital PCR could be useful for detecting HER2 amplification in patients with CRC who were resistant to anti-EGFR antibody therapy.

Acceleration of Hypertensive Cerebral Injury by the Inhibition of Xanthine-Xanthine Oxidase System in Stroke-Prone Spontaneously Hypertensive Rats

It is well-known that, in ischemic cerebral injury, a free radical and its byproducts are generated by xanthine-xanthine oxidase system and eliminated by scavengers such as superoxide dismutase (SOD), catalase, uric acid and ascorbic acid. To investigate the possible involvement of the xanthine-xanthine oxidase system in hypertensive cerebral injury, we examined chronological changes in uric acid level in the cerebral cortex and the effects of the inhibition of xanthine oxidase or catalase using stroke-prone spontaneously hypertensive rats (SHRSP). In young SHRSP, uric acid content was lower than age-matched Wistar-Kyoto rats (WKY), but in mature SHRSP strongly exposed to oxidative stress uric acid content had risen dramatically. Administration of allopurinol, an inhibitor of xanthine oxidase, caused a marked decrease in uric acid content. In these SHRSP, cerebral injury was much more intense compared to the control group. On the other hand, administration of aminotriazole, an inhibitor of catalase, did not affect the brain pathology of SHRSP, in spite of a mild reduction in tissue uric acid content. These results suggest that the xanthine-xanthine oxidase system is not the major source of free radical generation in hypertensive cerebral injury. Moreover, the results also suggest that tissue uric acid may have a key role for the incidence of hypertensive cerebral injury in SHRSP.

DS-8201a, a new HER2-targeting antibody–drug conjugate incorporating a novel DNA topoisomerase I inhibitor, overcomes HER2-positive gastric cancer T-DM1 resistance

Anti‐HER2 therapies are beneficial for patients with HER2‐positive breast or gastric cancer. T‐DM1 is a HER2‐targeting antibody–drug conjugate (ADC) comprising the antibody trastuzumab, a linker, and the tubulin inhibitor DM1. Although effective in treating advanced breast cancer, all patients eventually develop T‐DM1 resistance. DS‐8201a is a new ADC incorporating an anti‐HER2 antibody, a newly developed, enzymatically cleavable peptide linker, and a novel, potent, exatecan‐derivative topoisomerase I inhibitor (DXd). DS‐8201a has a drug‐to‐antibody‐ratio (DAR) of 8, which is higher than that of T‐DM1 (3.5). Owing to these unique characteristics and unlike T‐DM1, DS‐8201a is effective against cancers with low‐HER2 expression. In the present work, T‐DM1‐resistant cells (N87‐TDMR), established using the HER2‐positive gastric cancer line NCI‐N87 and continuous T‐DM1 exposure, were shown to be susceptible to DS‐8201a. The ATP‐binding cassette (ABC) transporters ABCC2 and ABCG2 were upregulated in N87‐TDMR cells, but HER2 overexpression was retained. Furthermore, inhibition of ABCC2 and ABCG2 by MK571 restored T‐DM1 sensitivity. Therefore, resistance to T‐DM1 is caused by efflux of its payload DM1, due to aberrant expression of ABC transporters. In contrast to DM1, DXd payload of DS‐8201a inhibited the growth of N87‐TDMR cells in vitro. This suggests that either DXd may be a poor substrate of ABCC2 and ABCG2 in comparison to DM1, or the high DAR of DS‐8201a relative to T‐DM1 compensates for increased efflux. Notably, N87‐TDMR xenograft tumor growth was prevented by DS‐8201a. In conclusion, the efficacy of DS‐8201a as a treatment for patients with T‐DM1‐resistant breast or gastric cancer merits investigation.

Mitochondrial abnormalities in hypertrophied myocardium of stroke-prone spontaneously hypertensive rats.

1. To clarify the pathogenesis of cardiac disorders in SHRSP which showed severe cardiac hypertrophy and myocardial degeneration in the hypertensive stage, restriction fragment length polymorphisms (RFLP) of mitochondrial DNA (mtDNA), and morphological and functional changes of mitochondria were examined.