Gastric cancer is one of the worldwide leading cancers which is highly prevalent in Eastern Asia. In Hong Kong, there were 1101 new cases and 687 cancer death in year 2011. So far gastric cancer is known to have poor prognosis and high relapse rate, for which a more effective therapy is sorely needed. With increasing knowledge in the role of HER2 in gastric cancer, a novel targeting agent, Trastuzumab, in combination with chemotherapy has become a promising personalized therapy for advanced gastric cancer and gastro-oesophageal junction cancer patients, particularly effective in HER2 positive patient subgroup. The clinical efficacy and safety of Trastuzumab therapy were ascertained by a recent worldwide phrase III randomized controlled trial called ToGA study in 2010. The assessment of the HER2 status has become crucial in selecting the right patient that will benefit most for the trastuzumab therapy. The aim of our study is to evaluate the local HER2 amplification rate in a group of gastric cancer patients and the associated tumour characteristics as well as sharing our technical experience in optimizing/standardizing the Silver ISH protocol including problem shooting in some difficult cases. From Oct 2012 to Apr 2014, we have accessed 68 requests of gastric cancer for HER2 status determination using Ventana Silver ISH assay, 61 were from stomach or gastro-oesophageal junction, 40 of them were endoscopic biopsy and 21 were resection specimens. Among them the majority were poorly differentiated (65.8%) and of intestinal sub-type (59.1%) according to Lauren classification. Thirteen out of 61 (21.3%) samples were found to be HER2 amplified. Majority of the HER2 positive cases were found in intestinal type and moderately differentiated adenocarcinoma. Eighty percent of the IHC 3+ cases and 29.6% of the IHC 2+ equivocal cases that required reflex tested with SISH were found to be HER2 amplified. There exists a great variation in the reported HER2 amplification rates in previous studies, which are apparently due to the difference in methodology and scoring algorithm apart from the different population groups. Recently, the introduction of the Hofmann’s modification on the scoring algorithm of HER2 assay dedicated for gastric cancer, and the increasing popularity in using DISH/SISH as a reliable alternative to FISH in detecting the HER2 status, have standardized the test and hence narrowed the variation. In order to achieve a more reliable staining result and accurate interpretation, optimization/ standardization of the analytical procedures, as well as the pre-analytical procedures become necessary. The standardization of the formalin fixation time seems to be a crucial factor in this regard. Therefore, the establishment of gastric cancer specimen handling guideline hospital-wide, and specific guideline recommendations for gastric cancer from ASCO/CAP are warranted. / published_or_final_version / Pathology / Master / Master of Medical Sciences

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisors: Babatunde Ogunnaike, Dept. of Chemical Engineering; and Boris N. Kholodenko, Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University. Includes bibliographical references.

Indiana University-Purdue University Indianapolis (IUPUI) / Cancer stem cells (CSCs) are proposed to play a major role in tumor progression, metastasis, and recurrence. The Human Epidermal growth factor Receptor 2 (HER2) gene is amplified and/or its protein product overexpressed in approximately 20% of breast cancers. HER2 overexpression is associated with increased CSCs, which may explain the aggressive phenotype and increased likelihood of recurrence for HER2+ breast cancers. Telomerase is reactivated in tumor cells, including CSCs, but has limited activity in normal tissues, providing support for the use of telomerase inhibition in anti-cancer therapy. Telomerase inhibition via an antagonistic oligonucleotide, imetelstat (GRN163L), has been shown to be effective in limiting cell growth in vitro and limiting tumor growth. Moreover, we have previously shown imetelstat can decrease metastases to the lungs, leading us to question if this is due to imetelstat targeting the CSC population. In this thesis, we investigated the effects of imetelstat on CSC and non-CSC populations of HER2+ breast cancer cell lines, as well as a triple negative breast cancer cell line, which lacks HER2 overexpression. Imetelstat inhibited telomerase activity in both CSC and non-CSC subpopulations. Moreover, imetelstat treatment alone and in combination with trastuzumab significantly reduced the CSC fraction and inhibited CSC functional ability, as shown by a significant decrease in mammosphere counts and invasive potential. Tumor growth rate was slower in combination treated mice compared to either drug alone. Additionally, there was a trend toward decreased CSC marker expression in imetelstat treated xenograft cells compared to vehicle control. The decrease in CSC marker expression we observed occurred prior to and after telomere shortening, suggesting imetelstat acts on the CSC subpopulation in telomere length dependent and independent mechanisms. Our study suggests addition of imetelstat to trastuzumab may enhance the effects of HER2 inhibition therapy.