The basal cell nevus syndrome (BCNS) is characterized by developmental abnormalities and by the postnatal occurrence of cancers, especially basal cell carcinomas (BCCs), the most common human cancer. Heritable mutations in BCNS patients and a somatic mutation in a sporadic BCC were identified in a human homolog of the Drosophila patched (ptc) gene. The ptc gene encodes a transmembrane protein that in Drosophila acts in opposition to the Hedgehog signaling protein, controlling cell fates, patterning, and growth in numerous tissues. The human PTC gene appears to be crucial for proper embryonic development and for tumor suppression.

Basal-cell carcinomas (BCCs) are the commonest human cancer. Insight into their genesis came from identification of mutations in the PATCHED gene (PTCH) in patients with the basal-cell nevus syndrome, a hereditary disease characterized by multiple BCCs and by developmental abnormalities. The binding of Sonic hedgehog (SHH) to its receptor, PTCH, is thought to prevent normal inhibition by PTCH of Smoothened (SMO), a seven-span transmembrane protein. According to this model, the inhibition of SMO signalling is relieved following mutational inactivation of PTCH in basal-cell nevus syndrome. We report here the identification of activating somatic missense mutations in the SMO gene itself in sporadic BCCs from three patients. Mutant SMO, unlike wild type, can cooperate with adenovirus E1A to transform rat embryonic fibroblast cells in culture. Furthermore, skin abnormalities similar to BCCs developed in transgenic murine skin overexpressing mutant SMO. These findings support the role of SMO as a signalling component of the SHH-receptor complex and provide direct evidence that mutated SMO can function as an oncogene in BCCs.

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Cancer cells are known to execute reprogramed metabolism of glucose, amino acids, and lipids. Here, we report a significant role of cholesterol metabolism in cancer metastasis. By employing label-free Raman spectromicroscopy, we found an aberrant accumulation of cholesteryl ester in human pancreatic cancer specimens and cell lines, mediated by acyl-CoA cholesterol acyltransferase-1 (ACAT-1) enzyme. Expression of ACAT-1 showed a correlation with poor patient survival. Abrogation of cholesterol esterification, either by an ACAT-1 inhibitor or by shRNA knockdown, significantly suppressed tumor growth and metastasis in an orthotopic mouse model of pancreatic cancer. Mechanically, ACAT-1 inhibition increased intracellular free cholesterol level, which was associated with elevated endoplasmic reticulum stress and caused apoptosis. Collectively, our results demonstrate a new strategy for treating metastatic pancreatic cancer by inhibiting cholesterol esterification.

Hedgehog (Hh) signaling is deregulated in multiple human cancers including pancreatic ductal adenocarcinoma (PDA). Because KRAS mutation represents one of the earliest genetic alterations and occurs almost universally in PDA, we hypothesized that oncogenic KRAS promotes pancreatic tumorigenesis in part through activation of the Hh pathway. Here, we report that oncogenic KRAS activates hedgehog signaling in PDA cells, utilizing a downstream effector pathway mediated by RAF/ MEK/MAPK but not phosphatidylinositol 3-kinase (PI3K)/ AKT. Oncogenic KRAS transformation of human pancreatic ductal epithelial cells increases GLI transcriptional activity, an effect that is inhibited by the MEK-specific inhibitors U0126 and PD98059, but not by the PI3K-specific inhibitor wortmannin. Inactivation of KRAS activity by a small interfering RNA specific for oncogenic KRAS inhibits GLI activity and GLI1 expression in PDA cell lines with activating KRAS mutation; the MEK inhibitors U0126 and PD98059 elicit a similar response. In addition, expression of the constitutively active form of BRAF E600 , but not myr-AKT, blocks the inhibitory effects of KRAS knockdown on Hh signaling. Finally, suppressing GLI activity leads to a selective attenuation of the oncogenic transformation activity of mutant KRAS-expressing PDA cells. These results demonstrate that oncogenic KRAS, through RAF/MEK/ MAPK signaling, is directly involved in the activation of the hedgehog pathway in PDA cells and that collaboration between these two signaling pathways may play an important role in PDA progression. Pancreatic ductal adenocarcinoma (PDA)2 is the fourth leading cause of cancer-related death for both men and women in the United States. It was estimated that in 2006 33,730 new cases would be diagnosed, and 32,300 would die from the disease (American Cancer Society Cancer Facts and Figures 2006). Therefore, PDA is one of the most lethal human diseases, with a 5-year survival rate of less than 4% and a median survival of less than 6 months.PDA is one of the better-characterized neoplasms at the genetic level. There are now sufficient clinical, genetic, and pathological data to support a tumor progression model for PDA in which the pancreatic ductal epithelium progresses from normal to increased grades of pancreatic intraepithelial neoplasia to invasive cancer (1, 2). Accompanying the progressive morphological changes is the sequential accumulation of genetic alterations in the KRAS oncogene and the tumor suppressors INK4A, p53, and SMAD4/DPC4, although these alterations have not been linked to the acquisition of specific histopathological attributes (3-5). In addition to these frequent genetic abnormalities, mutations in the tumor suppressors BRCA2, TGFBR1, and TGFBR2, the serine-threonine kinases AKT2 and LKB1/STK11, and certain DNA mismatch-repair genes represent other less common genetic events in PDA (6 -11).Aberrant RAS activation plays a critical role in tumorigenesis; activating RAS mutations are found in 30% of all human cancers (12). Of all human can...

Liver cancers, the majority of which are hepatocellular carcinomas (HCCs), rank as the fourth in cancer mortality worldwide and are the most rapidly increasing type of cancer in the United States. However, the molecular mechanisms underlying HCC development are not well understood. Activation of the hedgehog pathway is shown to be involved in several types of gastrointestinal cancers. Here, we provide evidence to indicate that hedgehog signaling activation occurs frequently in HCC. We detect expression of Shh, PTCH1 and Gli1 in 115 cases of HCC and in 44 liver tissues adjacent to the tumor. Expression of Shh is detectable in about 60% of HCCs examined. Consistent with this, hedgehog target genes PTCH1 and Gli1 are expressed in over 50% of the tumors, suggesting that the hedgehog pathway is frequently activated in HCCs. Of five cell lines screened, we found Hep3B, Huh7 and PLC/PRF/5 cells with detectable hedgehog target genes. Specific inhibition of hedgehog signaling in these three cell lines by smoothened (SMO) antagonist, KAAD-cyclopamine, or with Shh neutralizing antibodies decreases expression of hedgehog target genes, inhibits cell growth and results in apoptosis. In contrast, no effects are observed after these treatments in HCC36 and HepG2 cells, which do not have detectable hedgehog signaling. Thus, our data indicate that hedgehog signaling activation is an important event for development of human HCCs.

Mutations in PATCHED (PTC), the human homolog of the Drosophila patched gene, have been identified in most exons of the gene in patients with the basal cell nevus syndrome and in sporadic basal cell carcinomas. We have screened the 23 PTC exons for mutations using single strand conformation polymorphism analysis of DNA from 86 basal cell nevus syndrome probands, 26 sporadic basal cell carcinomas, and seven basal cell nevus syndrome-associated basal cell carcinomas. This screen identified mutations located in eight exons in 13 of the basal cell nevus syndrome patients and in three of the tumors. The most common mutations were frameshifts resulting in premature chain termination. These results provide further evidence for the crucial role of PTC as a tumor suppressor in human keratinocytes.

Abnormal activation of the hedgehog-signaling pathway is the pivotal abnormality driving the growth of basal cell carcinomas (BCCs), the most common type of human cancer. Antagonists of this pathway such as cyclopamine may therefore be useful for treatment of basal cell carcinomas and other hedgehog-driven tumors. We report here that chronic oral administration of cyclopamine dramatically reduces (ϳ66%) UVBinduced basal cell carcinoma formation in Ptch1 ؉/؊ mice. Fas expression is low in human and murine basal cell carcinomas but is up-regulated in the presence of the smoothened (SMO) antagonist, cyclopamine, both in vitro in the mouse basal cell carcinoma cell line ASZ001 and in vivo after acute treatment of mice with basal cell carcinomas. This parallels an elevated rate of apoptosis. Conversely, expression of activated SMO in C3H10T1/2 cells inhibits Fas expression. Fas/Fas ligand interactions are necessary for cyclopamine-mediated apoptosis in these cells, a process involving caspase-8 activation. Our data provide strong evidence that cyclopamine and perhaps other SMO antagonists are potent in vivo inhibitors of UVB-induced basal cell carcinomas in Ptch1 ؉/؊ mice and likely in humans because the majority of human basal cell carcinomas manifest mutations in PTCH1 and that a major mechanism of their inhibitory effect is through up-regulation of Fas, which augments apoptosis.