Therapies that target the EGF receptor (EGFR), such as gefitinib (IRESSA), are effective in a subset of patients with advanced non-small cell lung cancer (NSCLC). The differences in intracellular signaling networks between gefitinib-sensitive and -resistant NSCLCs remain poorly understood. In this study, we observe that gefitinib reduces phospho-Akt levels only in NSCLC cell lines in which it inhibits growth. To elucidate the mechanism underlying this observation, we compared immunoprecipitates of phosphoinositide 3-kinase (PI3K) between gefitinib-sensitive and -resistant NSCLC cell lines. We observe that PI3K associates with ErbB-3 exclusively in gefitinib-sensitive NSCLC cell lines. Gefitinib dissociates this complex, thereby linking EGFR inhibition to decreased Akt activity. In contrast, gefitinib-resistant cells do not use ErbB-3 to activate the PI3K͞Akt pathway. In fact, abundant ErbB-3 expression is detected only in gefitinib-sensitive NSCLC cell lines. Two gefitinib-sensitive NSCLC cell lines with endogenous distinct activating EGFR mutations (L858R and Del747-749), frequently observed in NSCLC patients who respond to gefitinib, also use ErbB-3 to couple to PI3K. Down-regulation of ErbB-3 by means of short hairpin RNA leads to decreased phospho-Akt levels in the gefitinibsensitive NSCLC cell lines, Calu-3 (WT EGFR) and H3255 (L858R EGFR), but has no effect on Akt activation in the gefitinib-resistant cell lines, A549 and H522. We conclude that ErbB-3 is used to couple EGFR to the PI3K͞Akt pathway in gefitinib-sensitive NSCLC cell lines harboring WT and mutant EGFRs.Akt ͉ EGF receptor

Tumor growth and metastasis require concomitant growth of new blood vessels, which are stimulated by angiogenic factors, including vascular endothelial growth factor (VEGF), secreted by most tumors. Whereas the angiogenic property and molecular mechanisms of VEGF have been well studied, the biological function of its related homolog, placenta growth factor (PlGF), is poorly understood. Here we demonstrate that PlGF-1, an alternatively spliced isoform of the PlGF gene, antagonizes VEGF-induced angiogenesis when both factors are coexpressed in murine fibrosarcoma cells. Overexpression of PlGF-1 in VEGF-producing tumor cells results in the formation of PlGF-1/VEGF heterodimers and depletion of the majority of mouse VEGF homodimers. The heterodimeric form of PlGF-1/VEGF lacks the ability to induce angiogenesis in vitro and in vivo. Similarly, PlGF-1/VEGF fails to activate the VEGFR-2-mediated signaling pathways. Further, PlGF-1 inhibits the growth of a murine fibrosarcoma by approximately 90% when PlGF-1-expressing tumor cells are implanted in syngeneic mice. In contrast, overexpression of human VEGF in murine tumor cells causes accelerated and exponential growth of primary fibrosarcomas and early hepatic metastases. Our data demonstrate that PlGF-1, a member of the VEGF family, acts as a natural antagonist of VEGF when both factors are synthesized in the same population of cells. The underlying mechanism is due to the formation of functionally inactive heterodimers.

Spinal muscular atrophy (SMA), an autosomal recessive neuromuscular disease, is the leading monogenic cause of infant mortality. Homozygous loss of the gene survival of motor neuron 1 (SMN1) causes the selective degeneration of lower motor neurons and subsequent atrophy of proximal skeletal muscles. The SMN1 protein product, survival of motor neuron (SMN), is ubiquitously expressed and is a key factor in the assembly of the core splicing machinery. The molecular mechanisms by which disruption of the broad functions of SMN leads to neurodegeneration remain unclear. We used an antisense oligonucleotide (ASO)-based inducible mouse model of SMA to investigate the SMN-specific transcriptome changes associated with neurodegeneration. We found evidence of widespread intron retention, particularly of minor U12 introns, in the spinal cord of mice 30 d after SMA induction, which was then rescued by a therapeutic ASO. Intron retention was concomitant with a strong induction of the p53 pathway and DNA damage response, manifesting as γ-H2A.X positivity in neurons of the spinal cord and brain. Widespread intron retention and markers of the DNA damage response were also observed with SMN depletion in human SH-SY5Y neuroblastoma cells and human induced pluripotent stem cell-derived motor neurons. We also found that retained introns, high in GC content, served as substrates for the formation of transcriptional R-loops. We propose that defects in intron removal in SMA promote DNA damage in part through the formation of RNA:DNA hybrid structures, leading to motor neuron death.

The delivery of anti-arthritic genes to the synovial lining of joints is being explored as a strategy for the treatment of rheumatoid arthritis. In this study, we have investigated the use of VSV-G pseudotyped, HIV-1-based lentiviral vectors for gene delivery to articular tissues. Recombinant lentivirus containing a beta-galactosidase/neomycin resistance fusion gene under control of the elongation factor (EF) 1alpha promoter efficiently transduced human and rat synoviocytes and chondrocytes in cell culture. When directly injected into the knees of rats, this vector transduced synovial lining cells, but not other articular tissues such as cartilage. We also constructed a lentiviral vector containing the human interleukin-1 receptor antagonist (IL1RA) cDNA and examined transgene expression in vitro and in vivo following injection into the knee joints of rats. In immunocompetent animals, intra-articular IL1RA expression was high and persisted, at a sharply declining rate, for approximately 20 days. In immunocompromised rats, however, lentivirus-mediated intra-articular expression of human IL1RA was found to persist for at least 6 weeks. Extra-articular expression of the transgene was minimal. These results indicate that lentiviral vectors are capable of efficient in vivo gene transfer to synovium and merit further investigation as a means of providing long-term expression for gene-based treatments of arthritis.

Clinical translation of gene-based therapies for arthritis could be accelerated by vectors capable of efficient intra-articular gene delivery and long-term transgene expression. Previously, we have shown that lentiviral vectors transduce rat synovium efficiently in vivo. Here, we evaluated the functional capacity of transgene expression provided by lentiviral-mediated gene delivery to the joint. To do this, we measured the ability of a lentiviral vector containing the cDNA for human interleukin-1 receptor antagonist (LV-hIL-1Ra) to suppress intra-articular responses to IL-1beta. Groups of rats were injected in one knee with 5 x 10(7) infectious units of LV-IL-1Ra. After 24 h, a range of doses of fibroblasts (3 x 10(3), 10(4), 3 x 10(4), or 10(5) cells) genetically modified to overexpress IL-1beta was injected into both knees. Intra-articular delivery of LV-hIL-1Ra strongly prevented swelling in all treated knees, even in those receiving the greatest dose of IL-1beta(+) cells. Cellular infiltration, cartilage erosion, and invasiveness of inflamed synovium were effectively prevented in LV-hIL-1Ra-treated knees and were significantly inhibited in contralateral joints. Beneficial effects were also observed systemically in the lentivirus-treated animals. Interestingly, intra-articular expression of the IL-1Ra transgene was found to increase in relation to the number of IL-1beta(+) cells injected. Further experiments using GFP suggest this is due to the proliferation of cells, stably modified by the integrative lentivirus, in response to inflammatory stimulation.

Recent research using rodent models of central nervous system gliomas indicates that a combination of gene transfer and drug treatment may be successful in killing tumor cells. In the present study, a mouse fibroblast-derived packaging cell line, psi 2, which releases a replication-defective retrovirus vector bearing the herpes simplex virus type 1 (HSV)-thymidine kinase (TK) gene, was grown with rat C6 tumor cells in the presence and absence of wild type Moloney murine leukemia virus (MoMLV). Consequently, tumor cells became sensitive to ganciclovir, which is selectively converted to a toxic nucleotide analog by HSV-TK. This killing effect was more effective in the presence than in the absence of wild type retrovirus both in culture and in subcutaneous tumors in nude mice. Tumors regressed in vivo and failed to regrow over a subsequent 10-day observation period after combined treatment with packaging cells, wild type MoMLV, and ganciclovir. This killing effect may be augmented by the ability of the helper retrovirus to package the vector in tumor cells and thus extend delivery of the HSV-TK gene to more tumor cells. This represents significant improvement in tumor therapy in this model system as compared with helper-free systems previously reported by the authors and others. Although additional improvements in the therapy can be envisioned, this approach may prove useful in combination with current modes of therapy for these insidious and lethal tumors.

Breast cancer development is a complex pathobiological process involving sequential genetic alterations in normal epithelial cells that results in uncontrolled growth in a permissive microenvironment. Accordingly, physiologically relevant models of human breast cancer that recapitulate these events are needed to study cancer biology and evaluate therapeutic agents. Here, we report the generation and utilization of the human breast cancer in mouse (HIM) model, which is composed of genetically engineered primary human breast epithelial organoids and activated human breast stromal cells. By using this approach, we have defined key genetic events required to drive the development of human preneoplastic lesions as well as invasive adenocarcinomas that are histologically similar to those in patients. Tumor development in the HIM model proceeds through defined histological stages of hyperplasia, DCIS to invasive carcinoma. Moreover, HIM tumors display characteristic responses to targeted therapies, such as HER2 inhibitors, further validating the utility of these models in preclinical compound testing. The HIM model is an experimentally tractable human in vivo system that holds great potential for advancing our basic understanding of cancer biology and for the discovery and testing of targeted therapies.cancer model ͉ human in mouse ͉ tissue reconstitution

Early-onset, generalized primary torsion dystonia (PTD) is an autosomal dominantly inherited disorder, characterized by involuntary movements and abnormal postures. The majority of cases are caused by a 3-bp deletion in the DYT1 gene on chromosome 9q34 that allows for specific genetic testing. We developed a simple, reliable, and cost-effective, PCR-based screening method for this mutation. Testing results from a cohort of 550 cases, including patients with different forms of dystonia and unclassified movement disorders, revealed that 72.2% of the patients with typical early-onset generalized PTD carried the GAG deletion in the DYT1 gene. Among 300 cases with late-onset focal/segmental dystonia, only 3 patients tested positive for the GAG deletion whereas 12.8% of the patients with an unclassified movement disorder were GAG positive. Our results confirm a genotype/phenotype correlation in early-onset PTD and show that application of strict clinical criteria leads to accurate prediction of carrier status in more than two-thirds of patients with this type of dystonia. Currently, we suggest that testing be recommended in individuals with age of onset of dystonia below 30 years and/or a positive family history of early-onset PTD. Testing is not recommended in patients with onset of symptoms after 30 years or in asymptomatic individuals under the age of 18.