Injury models have suggested that the lung contains anatomically and functionally distinct epithelial stem cell populations. We have isolated such a regional pulmonary stem cell population, termed bronchioalveolar stem cells (BASCs). Identified at the bronchioalveolar duct junction, BASCs were resistant to bronchiolar and alveolar damage and proliferated during epithelial cell renewal in vivo. BASCs exhibited self-renewal and were multipotent in clonal assays, highlighting their stem cell properties. Furthermore, BASCs expanded in response to oncogenic K-ras in culture and in precursors of lung tumors in vivo. These data support the hypothesis that BASCs are a stem cell population that maintains the bronchiolar Clara cells and alveolar cells of the distal lung and that their transformed counterparts give rise to adenocarcinoma. Although bronchiolar cells and alveolar cells are proposed to be the precursor cells of adenocarcinoma, this work points to BASCs as the putative cells of origin for this subtype of lung cancer.

SUMMARY PARAGRAPH MicroRNAs (miRNAs) are short non-coding RNAs expressed in different tissue and cell types that suppress the expression of target genes. As such, miRNAs are critical cogs in numerous biological processes1,2, and dysregulated miRNA expression is correlated with many human diseases. Certain miRNAs, called oncomiRs, play a causal role in the onset and maintenance of cancer when overexpressed. Tumors that depend on these miRNAs are said to display oncomiR addiction3–5. Some of the most effective anticancer therapies target oncogenes like EGFR and HER2; similarly, inhibition of oncomiRs using antisense oligomers (i.e. antimiRs) is an evolving therapeutic strategy6,7. However, the in vivo efficacy of current antimiR technologies is hindered by physiological and cellular barriers to delivery into targeted cells8. Here we introduce a novel antimiR delivery platform that targets the acidic tumor microenvironment, evades systemic clearance by the liver, and facilitates cell entry via a non-endocytic pathway. We found that the attachment of peptide nucleic acid (PNA) antimiRs to a peptide with a low pH-induced transmembrane structure (pHLIP) produced a novel construct that could target the tumor microenvironment, transport antimiRs across plasma membranes under acidic conditions such as those found in solid tumors (pH ~6), and effectively inhibit the miR-155 oncomiR in a mouse model of lymphoma. This study introduces a new paradigm in the use of antimiRs as anti-cancer drugs, which can have broad impacts on the field of targeted drug delivery.

Lung cancer is the leading cause of cancer deaths worldwide, yet few genetic markers of lung cancer risk useful for screening exist. The let-7 family-of-microRNAs (miRNA) are global genetic regulators important in controlling lung cancer oncogene expression by binding to the 3 ¶ untranslated regions of their target mRNAs. The purpose of this study was to identify single nucleotide polymorphisms (SNP) that could modify let-7 binding and to assess the effect of such SNPs on target gene regulation and risk for non-small cell lung cancer (NSCLC). let-7 complementary sites (LCS) were sequenced in the KRAS 3 ¶ untranslated region from 74 NSCLC cases to identify mutations and SNPs that correlated with NSCLC. The allele frequency of a previously unidentified SNP at LCS6 was characterized in 2,433 people (representing 46 human populations). The frequency of the variant allele is 18.1% to 20.3% in NSCLC patients and 5.8% in world populations. The association between the SNP and the risk for NSCLC was defined in two independent case-control studies. A case-control study of lung cancer from New Mexico showed a 2.3-fold increased risk (confidence interval, 1.1-4.6; P = 0.02) for NSCLC cancer in patients who smoked <40 pack-years. This association was validated in a second independent case-control study. Functionally, the variant allele results in KRAS overexpression in vitro. The LCS6 variant allele in a KRAS miRANA complementary site is significantly associated with increased risk for NSCLC among moderate smokers and represents a new paradigm for let-7 miRNAs in lung cancer susceptibility. [Cancer Res 2008;68(20):8535-40]

is an oncogenic microRNA that regulates several pathways involved in cell division and immunoregulation. It is overexpressed in numerous cancers, is often correlated with poor prognosis, and is thus a key target for future therapies. In this work we show that overexpression of miR-155 in lymphoid tissues results in disseminated lymphoma characterized by a clonal, transplantable pre-B-cell population of neoplastic lymphocytes. Withdrawal of miR-155 in mice with established disease results in rapid regression of lymphadenopathy, in part because of apoptosis of the malignant lymphocytes, demonstrating that these tumors are dependent on miR-155 expression. We show that systemic delivery of antisense peptide nucleic acids encapsulated in unique polymer nanoparticles inhibits miR-155 and slows the growth of these "addicted" pre-B-cell tumors in vivo, suggesting a promising therapeutic option for lymphoma/leukemia. oncogene | oncomiR addiction | nanotechnology M icroRNAs (miRNAs) govern nearly every biological process investigated (1-8). in particular is one of the most salient miRNAs, and although its role in immune function has been the subject of much attention (9-14), manifold studies also implicate it in cancer pathways, particularly those of hematopoietic origin (11,(15)(16)(17)(18)(19)(20)(21). miR-155 is induced in several lymphomas, such as diffuse large B-cell lymphomas, Hodgkin lymphomas, and subsets of Burkitt lymphomas (16,18,22), and ectopic expression of miR-155 in a transgenic mouse model leads to B-cell malignancy (15, 23). Furthermore, miR-155 induction in hematopoietic cells of myeloid origin results in a myeloproliferative pathology characterized by granulocyte/ monocyte expansion in lymphoid tissues (24,25). At the molecular level, miR-155 directly targets SH2-containing inositol phosphatase (SHIP1), a negative regulator of myeloid cell proliferation and survival. Furthermore, in diffuse large B-cell lymphomas, miR-155 induction and subsequent SHIP1 repression are TNF-α-dependent (23,24,26). Although these studies provide compelling evidence for miR-155 involvement in lymphoproliferative disease, the degree to which the survival of these cancers depend on maintained miR-155 expression has not been established, a crucial point to ascertain in determining whether or not inhibition of miR-155 has therapeutic promise.It is known that several protein-coding oncogenes such as Egfr, Myc, Ras, and Her2 (among others) exhibit oncogene addiction and that tumors can become dependent on maintained expression of these genes in mouse models (27)(28)(29). Recently, we described a miR-21-induced mouse model of lymphoma in which tumors were dependent on maintained expression of miR-21, demonstrating that miRNAs are a unique class of genes that mediate oncogene addiction (30).Toward cancer therapy, anti-miR molecules could potentially be used to attenuate oncogenic miRNAs, ultimately exploiting the miRNA dependence exhibited by certain tumors. In recent years, anti-miRs have emerged as useful tools for inhibiting ...