Exploring the Impact of In Vitro-Transcribed mRNA Impurities on Cellular Responses.

Advances in mRNA technology have enabled mRNA-based therapies to enter a new era of medicine. Such therapies benefit from a single, standardized in vitro transcription (IVT) manufacturing process applicable to a wide range of targets. This process includes several downstream purification steps, which aim to eliminate impurities that potentially affect safety and efficacy. However, it is not fully understood which impurities are the most critical; hence, some efforts are still needed to establish the correlation between RNA impurities and their role in limiting therapeutic efficacy. To study this relationship, we produced in vitro-transcribed mRNAs using several bacteriophage T7 RNA polymerases, including one wild-type and four engineered variants. Important attributes of the mRNA such as integrity, purity, and functional activity were then measured using advanced physicochemical and cellular assays. For impurities including abortive transcripts, mRNAs containing partial poly(A) tails, and double-stranded (ds)RNA byproducts, structure-function relationships have been established by tracking cellular responses (i.e., protein expression, reactogenicity) in multiple cell models. By varying the T7 RNA polymerase, different levels of sense-antisense dsRNA byproducts were measured by mass photometry, contributing directly to immunological reactogenicity in bone marrow-derived dendritic cells. T7 RNA polymerase differences with regard to short (<20 nucleotides) 3'-loopback dsRNA byproducts were also further investigated using native mass spectrometry by precisely resolving these impurities at the nucleotide level. Overall, this study highlights the importance of developing sensitive and advanced analytical methods to characterize IVT mRNA impurities and understand their interaction with cellular machinery in order to ensure quality control of RNA-based therapies.

Effects of asiaticoside on the model of gestational diabetes mellitus in HTR-8/svneo cells via PI3K/AKT pathway.

BACKGROUND: Asiaticoside (AS) has been reported to improve the changes induced by high glucose stimulation, and it may have potential therapeutic effects on gestational diabetes mellitus (GDM). This study aims to explore the effect of AS on the cell model of GDM and the action mechanism of the PI3K/AKT pathway. METHODS: The GDM model was established in HTR-8/Svneo cells with a high glucose (HG) medium. After the cytotoxicity assay of AS, cells were divided into the control group, HG group and HG + AS group to conduct control experiment in cells. The cell proliferation and migration were detected by CCK-8 assay and scratch test, respectively. The mRNA levels of PI3K, AKT2, mTORC1, and GLUT4 in PI3K/AKT signalling pathway were measured by RT-PCR, and the protein expressions of these signalling molecules were monitored by western blot. RESULTS: AS showed a promotion effect on the cell proliferation rate of HTR-8/Svneo cells, and 80 µmol/L AS with a treatment time of 48 h had no cytotoxicity. The cell proliferation rate, migration rate, mRNA levels and protein expressions of PI3K, AKT2, mTORC1, and GLUT4 in the HG group were significantly lower than those in the control group, which were significantly increased in the HG + AS group (p < 0.05). CONCLUSIONS: AS can facilitate the cell proliferation and migration in the cell model of GDM, and might play a role in GDM treatment via PI3K/AKT pathway.

Asiaticoside possesses various pharmacological effects and has been reported to show a beneficial effect on the treatment of diabetes mellitus. This research firstly investigated the effect and mechanism of asiaticoside on gestational diabetes mellitus, and found that asiaticoside could facilitate the cell proliferation and migration of HTR-8/Svneo cells treated with high glucose, and affect the signalling molecules of PI3K/AKT pathway. Therefore, asiaticoside may be a novel useful therapeutic drug in the treatment of gestational diabetes mellitus.

Assessing TCR identity, knock-in efficiency, and potency for individualized TCR-T cell therapy.

Advances in mass spectrometry, genome sequencing techniques, and bioinformatic strategies have accelerated the discovery of cancer-specific neoantigens. Tumors express multiple immunogenic neoantigens, and neoantigen-specific T cell receptors (TCRs) can be identified in peripheral blood's mononuclear cells in cancer patients. Therefore, individualized TCR-based therapies are a promising approach whereby multiple neoantigen-specific TCRs can be selected in each patient, potentially leading to a highly effective treatment for cancer patients. We developed three multiplex analytical assays to determine the quality attributes of the TCR-T cell drug product with a mixture of five engineered TCRs. The identity of each TCR was determined by two NGS-based methods, Illumina MiSeq and PacBio platforms. This approach not only confirms the expected TCR sequences but also differentiates them by their variable regions. The five individual TCR and total TCR knock-in efficiencies were measured by droplet digital PCR using specific reverse primers. A potency assay based on transfection of antigen-encoding-RNA was developed to assess the dose-dependent activation of T cells for each TCR by measuring the surface activation marker CD137 expression and cytokine secretion. This work provides new assays to characterize individualized TCR-T cell products and insights into quality attributes for the control strategy.

Asiaticoside hampers epithelial-mesenchymal transition by promoting PPARG expression and suppressing P2RX7-mediated TGF-ß/Smad signaling in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) accounts for 10-20% of all human ductal adenocarcinomas and has a poor prognosis relative to other subtypes because of its high propensity to develop metastases. Here, the anticancer effects of asiaticoside (AC) against TNBC and the possible underlying mechanism were examined. We found that AC inhibited the TGF-ß1 expression and the SMAD2/3 phosphorylation in TNBC cells, thereby impairing the TGF-ß/SMAD signaling. AC inhibited the migration, invasion, and epithelial-mesenchymal transition (EMT) of TNBC cells by suppressing the TGF-ß/SMAD signaling. Meanwhile, AC inhibited the lung metastasis of TNBC cells in vivo and the expression of p-SMAD2/3 and vimentin, and increased the expression of E-cadherin and ZO-1 in the lung. Peroxisome proliferator activated receptor gamma (PPARG) was identified as a potential target of AC. AC increased PPARG expression, while PPARG knockdown attenuated the therapeutic effect of AC. AC-mediated PPARG overexpression suppressed the transcription of P2X purinoceptor 7 (P2RX7). The restoration of P2RX7 reversed the therapeutic effect of AC. These results suggested that AC blocked P2RX7-mediated TGF-ß/SMAD signaling by increasing PPARG expression, thereby suppressing EMT in TNBC.

C-Terminal Lysine Processing of IgG in Human Suction Blister Fluid: Implications for Subcutaneous Administration.

C-terminal lysine (CTK) is often classified as a potential critical quality attribute for therapeutic antibodies being developed for subcutaneous (SC) administration because of its potential to impact antibody SC bioavailability/pharmacokinetics (PK). This classification both inflates development costs and increases comparability risks for SC administration of antibodies. However, prior risk assessments of CTK have not fully considered biotransformation of CTK in the SC space, which may play an important role given that circulating carboxypeptidases in humans rapidly process CTK on intravenously administered antibodies. Here, CTK biotransformation in biofluid derived from human SC space was investigated. The representative fluid from the human SC space was sampled from 10 healthy human subjects using the suction blister method. Glycosylated antibody containing high levels of CTK (expressed using a carboxypeptidase D CRISPR/Cas9 knockout CHO cell line) was incubated in the collected suction blister fluids (SBFs), recovered using cognate antigen pulldowns, and characterized for remaining CTK levels using intact and reduced liquid chromatography-mass spectrometry (LC-MS) analysis. CTK processing (i.e., carboxypeptidase activity) was evident in all SBF and exhibited first-order kinetics with rate constants of 2.18 ± 0.57 d-1 (at 37 °C). PK simulations that integrated CTK processing pathways and their associated rate constants were subsequently performed using a range of clinically observed PK parameters for therapeutic antibodies, including atezolizumab- and pertuzumab-specific parameters. The impact of CTK content (even up to 100%) on SC PK outcomes such as bioavailability and Ctrough were modest (<14%) for all combinations of PK parameters tested in the sensitivity analysis. This study forms the cornerstone data package for derisking CTK as a PK liability for antibody SC programs and highlights the usefulness of fully considering biotransformation during product quality criticality assessments.

Balancing the Affinity and Pharmacokinetics of Antibodies by Modulating the Size of Charge Patches on Complementarity-Determining Regions.

A localized positive charge on IgG (referred to as a "charge patch") shows an adverse effect on pharmacokinetics (PK), so it would seem to be best practice to avoid charge patches during the discovery stage and closely monitor charge interactions during the development process. In certain circumstances, however, charge patches are required for target binding, in which case completely removing charge patches is not feasible. Therefore, quantitative measurement of a charge patch and its impact on PK is critical to the success of therapeutic antibody development. In this article, we generated mutations of a recombinant human antibody (referred to as mAb1) with disrupted charge patches to investigate how charge patches on IgG antibodies impact both target-binding affinity and PK-related factors. We conclude that it is important to modulate the size of the charge patch in order to balance target-binding affinity and PK.

Maximizing antibody production in a targeted integration host by optimization of subunit gene dosage and position.

Historically, therapeutic protein production in Chinese hamster ovary (CHO) cells has been accomplished by random integration (RI) of expression plasmids into the host cell genome. More recently, the development of targeted integration (TI) host cells has allowed for recombination of plasmid DNA into a predetermined genomic locus, eliminating one contributor to clone-to-clone variability. In this study, a TI host capable of simultaneously integrating two plasmids at the same genomic site was used to assess the effect of antibody heavy chain and light chain gene dosage on antibody productivity. Our results showed that increasing antibody gene copy number can increase specific productivity, but with diminishing returns as more antibody genes are added to the same TI locus. Random integration of additional antibody DNA copies in to a targeted integration cell line showed a further increase in specific productivity, suggesting that targeting additional genomic sites for gene integration may be beneficial. Additionally, the position of antibody genes in the two plasmids was observed to have a strong effect on antibody expression level. These findings shed light on vector design to maximize production of conventional antibodies or tune expression for proper assembly of complex or bispecific antibodies in a TI system.

Probing the importance of clonality: Single cell subcloning of clonally derived CHO cell lines yields widely diverse clones differing in growth, productivity, and product quality.

In the past few decades, a large variety of therapeutic antibodies and proteins have been expressed in Chinese hamster ovary (CHO) cells. This mammalian expression system is robust, scalable, relatively inexpensive, and importantly allows for post-translational modifications that are important for some therapeutic proteins. Historically, CHO cell lines were derived from colonies of cells grown in semi-solid or liquid plates using either serum-containing or serum-free media. Current advancements in cell sorting and imaging technologies have allowed for isolating and imaging single cell progenitors at the seeding step, significantly increasing the probability of isolating clonally derived cell lines. However, it is debatable how much population heterogeneity can be eliminated when clonally derived cell lines, originated from a single cell progenitor, are scaled up. To further investigate this phenomenon, we subcloned two different clonally derived (day 0 imaged and visually inspected) cell lines expressing antibody-X. The results showed that when six randomly chosen subclones of each line were evaluated in a production assay, these subclones displayed a range of variation in titer, specific productivity, growth, and product quality attributes. Some subclones displayed variations in transgene copy numbers. Additionally, clonal derivation did not assure stability of the derived cell lines. Our findings show that cell heterogeneity exists in a population even when derived from a single cell progenitor. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:624-634, 2018.

A strategy to accelerate protein production from a pool of clones in Chinese hamster ovary cells for toxicology studies.

In the biopharmaceutical industry, a clonally derived cell line is typically used to generate material for investigational new drug (IND)-enabling toxicology studies. The same cell line is then used to generate material for clinical studies. If a pool of clones can be used to produce material for IND-enabling toxicology studies (Pool for Tox (PFT) strategy) during the time a lead clone is being selected for clinical material production, the toxicology studies can be accelerated significantly (approximately 4 months at Genentech), leading to a potential acceleration of 4 months for the IND submission. We explored the feasibility of the PFT strategy with three antibodies-mAb1, mAb2, and mAb3-at the 2 L scale. For each antibody, two lead cell lines were identified that generated material with similar product quality to the material generated from the associated pool. For two antibody molecules, mAb1 and mAb2, the material generated by the lead cell lines from 2 L bioreactors was tested in an accelerated stability study and was shown to have stability comparable to the material generated by the associated pool. Additionally, we used this approach for two antibody molecules, mAb4 and mAb5, at Tox and GMP production. The materials from the Tox batch at 400 L scale and three GMP batches at 2000 L scale have comparable product quality attributes for both molecules. Our results demonstrate the feasibility of using a pool of clonally derived cell lines to generate material of similar product quality and stability for use in IND-enabling toxicology studies as was derived from the final production clone, which enabled significant acceleration of timelines into clinical development. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1449-1455, 2017.

Evaluation of heavy chain C-terminal deletions on productivity and product quality of monoclonal antibodies in Chinese hamster ovary (CHO) cells.

Monoclonal antibodies (mAbs) have been well established as potent therapeutic agents and are used to treat many different diseases. During cell culture production, antibody charge variants can be generated by cleavage of heavy chain (HC) C-terminal lysine and proline amidation. Differences in levels of charge variants during manufacturing process changes make it challenging to demonstrate process comparability. In order to reduce heterogeneity and achieve consistent product quality, we generated and expressed antibodies with deletion of either HC C-terminal lysine (-K) or lysine and glycine (-GK). Interestingly, clones that express antibodies lacking HC C-terminal lysine (-K) had considerably lower specific productivities compared to clones that expressed either wild type antibodies (WT) or antibodies lacking HC glycine and lysine (-GK). While no measurable differences in antibody HC and LC mRNA levels, glycosylation and secretion were observed, our analysis suggests that the lower specific productivity of clones expressing antibody lacking HC C-terminal lysine was due to slower antibody HC synthesis and faster antibody degradation. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:786-794, 2017.

Efficient production of bispecific IgG of different isotypes and species of origin in single mammalian cells.

Bispecific IgG production in single host cells has been a much sought-after goal to support the clinical development of these complex molecules. Current routes to single cell production of bispecific IgG include engineering heavy chains for heterodimerization and redesign of Fab arms for selective pairing of cognate heavy and light chains. Here, we describe novel designs to facilitate selective Fab arm assembly in conjunction with previously described knobs-into-holes mutations for preferential heavy chain heterodimerization. The top Fab designs for selective pairing, namely variants v10 and v11, support near quantitative assembly of bispecific IgG in single cells for multiple different antibody pairs as judged by high-resolution mass spectrometry. Single-cell and in vitro-assembled bispecific IgG have comparable physical, in vitro biological and in vivo pharmacokinetics properties. Efficient single-cell production of bispecific IgG was demonstrated for human IgG1, IgG2 and IgG4 thereby allowing the heavy chain isotype to be tailored for specific therapeutic applications. Additionally, a reverse chimeric bispecific IgG2a with humanized variable domains and mouse constant domains was generated for preclinical proof-of-concept studies in mice. Efficient production of a bispecific IgG in stably transfected mammalian (CHO) cells was shown. Individual clones with stable titer and bispecific IgG composition for >120 days were readily identified. Such long-term cell line stability is needed for commercial manufacture of bispecific IgG. The single-cell bispecific IgG designs developed here may be broadly applicable to biotechnology research, including screening bispecific IgG panels, and to support clinical development.

Intravenous transfusion of endothelial progenitor cells that overexpress vitamin D receptor inhibits atherosclerosis in apoE-deficient mice.

Endothelial progenitor cells (EPCs) are widely used for angiogenic therapies, as well as predictive biomarkers to assess cardiovascular disease risk. However, it is unknown that whether overexpressed vitamin D receptor (VDR) in EPCs could help EPCs counteracting atherosclerotic risks. Here, we study intravenous transplantation of genetically modified EPCs over-expressing VDR in regulating endothelial dysfunction and spontaneously arising atherosclerotic plaques of ApoE-deficient mice. Firstly, we found that over-expression of VDR in EPCs could reduce atherosclerotic plaque formation in transplanted ApoE-/- mice. In addition, the concentration of serum HDL-C in ovVDR-EPCs group was much higher than that in control groups (ApoE-/- mice without injection or injected with fresh medium or adenovirus vector). While concentrations of serum total cholesterol, LDL-C, apoB and Lp (a) were negatively correlated with the expression level of VDR. What's more, improved serum concentration of NO and elevated serum and vessel wall expression of eNOS were observed in ovVDR-EPCs group. Furthermore, reduced expression and activity of MMP2, and elevated expression and activity of TIMP2 were detected in ovVDR-EPCs group. Taken together, intravenous transfusion of EPCs that overexpress VDR significantly inhibited atherosclerosis in ApoE-deficient mice and could be used as a potential method for angiogenic therapy.

Evaluation of Heavy-Chain C-Terminal Deletion on Product Quality and Pharmacokinetics of Monoclonal Antibodies.

Due to their potential influence on stability, pharmacokinetics, and product consistency, antibody charge variants have attracted considerable attention in the biotechnology industry. Subtle to significant differences in the level of charge variants and new charge variants under various cell culture conditions are often observed during routine manufacturing or process changes and pose a challenge when demonstrating product comparability. To explore potential solutions to control charge heterogeneity, monoclonal antibodies (mAbs) with native, wild-type C-termini, and mutants with C-terminal deletions of either lysine or lysine and glycine were constructed, expressed, purified, and characterized in vitro and in vivo. Analytical and physiological characterization demonstrated that the mAb mutants had greatly reduced levels of basic variants without decreasing antibody biologic activity, structural stability, pharmacokinetics, or subcutaneous bioavailability in rats. This study provides a possible solution to mitigate mAb heterogeneity in C-terminal processing, improve batch-to-batch consistency, and facilitate the comparability study during process changes.

Carboxypeptidase D is the only enzyme responsible for antibody C-terminal lysine cleavage in Chinese hamster ovary (CHO) cells.

Heterogeneity of C-terminal lysine levels often observed in therapeutic monoclonal antibodies is believed to result from the proteolysis by endogenous carboxypeptidase(s) during cell culture production. Identifying the responsible carboxypeptidase(s) for C-terminal lysine cleavage in CHO cells would provide valuable insights for antibody production cell culture processes development and optimization. In this study, five carboxypeptidases, CpD, CpM, CpN, CpB, and CpE, were studied for message RNA (mRNA) expression by qRT-PCR analysis in two most commonly used blank hosts (DUXB-11 derived DHFR-deficient DP12 host and DHFR-positive CHOK1 host), used for therapeutic antibody production, as well an antibody-expressing cell line derived from each host. Our results showed that CpD had the highest mRNA expression. When CpD mRNA levels were reduced by RNAi (RNA interference) technology, C-terminal lysine levels increased, whereas there was no obvious change in C-terminal lysine levels when a different carboxypeptidase mRNA level was knocked down suggesting that carboxypeptidase D is the main contributor for C-terminal lysine processing. Most importantly, when CpD expression was knocked out by CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) technology, C-terminal lysine cleavage was completely abolished in CpD knockout cells based on mass spectrometry analysis, demonstrating that CpD is the only endogenous carboxypeptidase that cleaves antibody heavy chain C-terminal lysine in CHO cells. Hence, our work showed for the first time that the cleavage of antibody heavy chain C-terminal lysine is solely mediated by the carboxypeptidase D in CHO cells and our finding provides one solution to eliminating C-terminal lysine heterogeneity for therapeutic antibody production by knocking out CpD gene expression. Biotechnol. Bioeng. 2016;113: 2100-2106. © 2016 Wiley Periodicals, Inc.

Fast identification of reliable hosts for targeted cell line development from a limited-genome screening using combined φC31 integrase and CRE-Lox technologies.

The use of targeted integration (TI) in cell line development (CLD) usually introduces one copy of a recombinant gene into a predetermined transcriptionally active locus. This reduces the heterogeneity typically associated with traditional random integration (RI) CLD with regards to varied productivity and instability, resulting from diverse chromosomal influences, varied copy numbers, and repeat-induced rearrangement. As such, TI CLD offers the hope of a predictable and consistent CLD process for establishing stable clones. However, given the low copy number, cell lines established from a TI CLD process tend to exhibit low productivity. Here, we describe our nonviral-based approach for quickly establishing and identifying TI hosts from a limited genome screening. Importantly, the TI hosts identified are consistent and reliable in supporting the production of diverse antibodies regardless of antibody subclass (IgG1 vs. IgG4) or prior traditional CLD performance (relatively easy vs. difficult to express antibodies). Moreover, an approximately twofold increase in titer can be achieved by using a CRE recombinase-mediated cassette exchange (RMCE) strategy with an exchange vector carrying two units of the antibody gene. Two RMCE hosts that were established were able to produce up to ∼ 1.7 and 2 g/L of antibodies in nonoptimized fed-batch shake flask production cultures with chemically defined media. Potentially, this strategy may be applied to the production of bispecific antibodies with a fast turnaround time.

Chinese hamster ovary K1 host cell enables stable cell line development for antibody molecules which are difficult to express in DUXB11-derived dihydrofolate reductase deficient host cell.

Therapeutic monoclonal antibodies (mAb) are often produced in Chinese hamster ovary (CHO) cells. Three commonly used CHO host cells for generating stable cell lines to produce therapeutic proteins are dihydrofolate reductase (DHFR) positive CHOK1, DHFR-deficient DG44, and DUXB11-based DHFR deficient CHO. Current Genentech commercial full-length antibody products have all been produced in the DUXB11-derived DHFR-deficient CHO host. However, it has been challenging to develop stable cell lines producing an appreciable amount of antibody proteins in the DUXB11-derived DHFR-deficient CHO host for some antibody molecules and the CHOK1 host has been explored as an alternative approach. In this work, stable cell lines were developed for three antibody molecules in both DUXB11-based and CHOK1 hosts. Results have shown that the best CHOK1 clones produce about 1 g/l for an antibody mAb1 and about 4 g/l for an antibody mAb2 in 14-day fed batch cultures in shake flasks. In contrast, the DUXB11-based host produced ∼0.1 g/l for both antibodies in the same 14-day fed batch shake flask production experiments. For an antibody mAb3, both CHOK1 and DUXB11 host cells can generate stable cell lines with the best clone in each host producing ∼2.5 g/l. Additionally, studies have shown that the CHOK1 host cell has a larger endoplasmic reticulum and higher mitochondrial mass.

Understanding the intracellular effect of enhanced nutrient feeding toward high titer antibody production process.

One of the major goals in cell culture process development for therapeutic antibody production is to develop methods to reach high titer in classical fed-batch processes. This goal is often achieved through the optimizations of expression vector, cell line, media and cell culture process controls to increase cell specific productivity, viable cell density, and culture longevity. During process optimization for a selected production cell line, cell specific productivity (qP) can vary significantly with culture conditions. Therefore, identifying strategies to maintain maximal specific productivity throughout the entire fed-batch culture and to eliminate cellular/process bottlenecks that prevent high levels of antibody production would be crucial for further advancements in this area. In this work, specific productivity was increased and maintained at high level throughout the course of the culture by the optimization of feed media and feeding strategy. Through the enhancement of nutrient feeding, final titer was increased by 2.5-fold from the platform fed-batch process and reached 7.5 g/L. In addition, further insight upon possible cellular bottlenecks in high yield antibody production was obtained by comparing the levels of heavy chain (HC) and light chain (LC) mRNA and the levels of intracellular antibody between the non-optimized and optimized feeding processes. The mRNA levels of the two processes were measured and exhibited no significant difference suggesting that transcription is not the bottleneck. When intracellular antibody level was studied, the relatively constant level of HC, LC, and intact antibody between days 9 and 14 suggested that translation could be the rate-limiting step under the non-optimized nutrient feeding condition due to the dramatic drop of qP to roughly zero which correlated with the depletion of tyrosine as one of the key amino acids for protein synthesis. Finally, accumulation of unassembled HC but not intact antibody was observed at days 14-18 under the enhanced feeding condition, implying that folding and assembly may be the bottleneck toward the end of the culture.

Importance of cellular microenvironment and circulatory dynamics in B cell immunotherapy.

B cell immunotherapy has emerged as a mainstay in the treatment of lymphomas and autoimmune diseases. Although the microenvironment has recently been demonstrated to play critical roles in B cell homeostasis, its contribution to immunotherapy is unknown. To analyze the in vivo factors that regulate mechanisms involved in B cell immunotherapy, we used a murine model for human CD20 (hCD20) expression in which treatment of hCD20(+) mice with anti-hCD20 mAbs mimics B cell depletion observed in humans. We demonstrate in this study that factors derived from the microenvironment, including signals from the B cell-activating factor belonging to the TNF family/BLyS survival factor, integrin-regulated homeostasis, and circulatory dynamics of B cells define distinct in vivo mechanism(s) and sensitivities of cells in anti-hCD20 mAb-directed therapies. These findings provide new insights into the mechanisms of immunotherapy and define new opportunities in the treatment of cancers and autoimmune diseases.

Evidence for lack of enhanced hedgehog target gene expression in common extracutaneous tumors.

Abnormal hedgehog signaling, most commonly caused by loss of PTCH1 inhibitor activity,drives tumorigenesis of basal cell carcinomas (BCCs). To assess whether other tumors also have abnormal hedgehog signaling, we have assayed RNA from common cancers at nine different sites for levels of expression of hedgehog target genes that are up-regulated uniformly in BCCs. We report here that such dysregulation appears not to be common in the types of non-BCC cancers studied, indicating that the molecular pathogenesis of BCCs, like their frequency and behavior, differs markedly from that of most other cancers.