Maria S. Romero

We show that two commonly occurring epidermal growth factor receptor (EGFR) somatic mutations, L858R and an in-frame deletion mutant, Del(746-750), exhibit distinct enzymatic properties relative to wild-type EGFR and are differentially sensitive to erlotinib. Kinetic analysis of the purified intracellular domains of EGFR L858R and EGFR Del(746-750) reveals that both mutants are active but exhibit a higher K(M) for ATP and a lower K(i) for erlotinib relative to wild-type receptor. When expressed in NR6 cells, a cell line that does not express EGFR or other ErbB receptors, both mutations are ligand dependent for receptor activation, can activate downstream EGFR signaling pathways, and promote cell cycle progression. As expected from the kinetic analysis, the EGFR Del(746-752) is more sensitive to erlotinib inhibition than the EGFR L858R mutant. Further characterization shows that these mutations promote ligand-dependent and anchorage-independent growth, and cells harboring these mutant receptors form tumors in immunocompromised mice. Analysis of tumor lysates reveals that the tumorigenicity of the mutant EGFR cell lines may be due to a differential pattern of mutant EGFR autophosphorylation as compared with wild-type receptor. Significant inhibition of tumor growth, in mice harboring wild-type EGFR receptors, is only observed at doses of erlotinib approaching the maximum tolerated dose for the mouse. In contrast, the growth of mutant tumors is inhibited by erlotinib treatment at approximately one third the maximum tolerated dose. These findings suggest that EGFR somatic mutations directly influence both erlotinib sensitivity and cellular transformation.

A striking feature of colon tumors is the significant reduction of goblet cells. Although targeted deletion of Math1 in mice leads to a loss of intestinal secretory cells, including goblet cells, the role of Hath1 in colon tumorigenesis remains unknown. Here we report that Hath1, the human ortholog of Math1, was dramatically down-regulated in colon tumor samples and colon cancer cell lines. Overexpression of Hath1 in HT29, an aggressive colon cancer cell line, resulted in a significant inhibition on cell proliferation, anchorage-independent growth in soft agar and, more importantly, growth of human colon cancer cell xenografts in athymic nude mice. Such inhibition was accompanied by altered expression of a goblet cell differentiation marker, MUC2, and cell cycle regulators cyclin D1 and p27kip1. Hath1 expression also was up-regulated on inhibition of the Wnt pathway, which has been well implicated in colon tumorigenesis. Hence, this study suggests that Hath1 may be a novel factor downstream of the Wnt pathway capable of suppressing anchorage-independent growth of colon cancer cell lines. More importantly, this study is the first to establish a link between down-regulation of Hath1 expression and colon tumorigenesis.

This is a review of the fine-needle aspirates (FNAs) of nine pilomatrixomas (PMs) found in a series of 1,500 FNAs performed on skin nodules. The objective is to determine and list the cytologic findings that might mislead the less-experienced cytopathologist and to give him advice on how to avoid such errors. The following recommendations are made: 1) The FNAs should be carried out and the smears interpreted by the same person. 2) Clinical data, particularly age and location, are of paramount importance. 3) Shadow cells are pathognomonic of PMs. 4) Basaloid nuclei with prominent nucleoli should not be overdiagnosed. 5) Use both Papanicolaou and Diff-Quik stains. 6) Think of PM when performing and interpreting aspirations from subcutaneous growths located in the head and neck of young persons.

The smears of fine-needle aspirates corresponding to 137 histologically proven basal-cell carcinomas (BCCs) were reviewed. Satisfactory for evaluation were 127 smears; the remaining 10 were unsatisfactory. In 124 cases (97.6%), the cytologic diagnoses coincided with the histologic ones. The remaining 3 were false negatives, and the subsequent histologic correlation demonstrated superficial BCC missed by the needle. The cytologic criteria that permitted a diagnosis of BCC were: variable-sized and irregular-shaped cohesive epithelial clusters, round to oval monomorphic nuclei, bland chromatin pattern, and sparse cytoplasm. In 35 cases, a panel of antibodies was used in the smears and in the respective histologic sections. Epithelial clusters of BCC showed an intense and diffuse positivity for AE-3 and BerEP4, while UEAI and AE-1 were negative. Although HMB45 and S100-A tested negative in the epithelial clusters, a faint and sparse focal positivity for HMB45 and S-100A was seen in some clusters. This positivity is believed to correspond to just a few normal melanocytes and Langerhans cells trapped in the neoplastic epithelial clusters. In the histologic correlates, the same results were obtained, although HMB45 positivity was more conspicuous at the periphery of the neoplastic nests.