Oncogenic Kras is required for both the initiation and maintenance of pancreatic cancer in mice

Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan, USA.
The Journal of clinical investigation (Impact Factor: 13.22). 02/2012; 122(2):639-53. DOI: 10.1172/JCI59227
Source: PubMed


Pancreatic cancer is almost invariably associated with mutations in the KRAS gene, most commonly KRASG12D, that result in a dominant-active form of the KRAS GTPase. However, how KRAS mutations promote pancreatic carcinogenesis is not fully understood, and whether oncogenic KRAS is required for the maintenance of pancreatic cancer has not been established. To address these questions, we generated two mouse models of pancreatic tumorigenesis: mice transgenic for inducible KrasG12D, which allows for inducible, pancreas-specific, and reversible expression of the oncogenic KrasG12D, with or without inactivation of one allele of the tumor suppressor gene p53. Here, we report that, early in tumorigenesis, induction of oncogenic KrasG12D reversibly altered normal epithelial differentiation following tissue damage, leading to precancerous lesions. Inactivation of KrasG12D in established precursor lesions and during progression to cancer led to regression of the lesions, indicating that KrasG12D was required for tumor cell survival. Strikingly, during all stages of carcinogenesis, KrasG12D upregulated Hedgehog signaling, inflammatory pathways, and several pathways known to mediate paracrine interactions between epithelial cells and their surrounding microenvironment, thus promoting formation and maintenance of the fibroinflammatory stroma that plays a pivotal role in pancreatic cancer. Our data establish that epithelial KrasG12D influences multiple cell types to drive pancreatic tumorigenesis and is essential for tumor maintenance. They also strongly support the notion that inhibiting KrasG12D, or its downstream effectors, could provide a new approach for the treatment of pancreatic cancer.

Download full-text


Available from: Stefanie Galbán, Mar 25, 2014
  • Source
    • "Transgenic mouse models represent another distinct system that have been utilized in cancer research. These models are most often used to assess the impact of relevant oncogenic mutations to tumorigenesis and therapeutic response for a variety of human cancers including pancreatic ductal adenocarcinoma [29], [30], soft-tissue sarcoma [31], lung adenocarcinoma [32], HNC [33] and many others. The scope of questions that can be examined by transgenic mice is quite broad as exemplified by prior studies on transgenic mice expressing human papillomavirus (HPV) oncogenes in which interactions between these specific oncogenes with fanconi anemia deficiency genes [34], estrogen and cervical cancer progression [35], and oncoprotein expression in relation to lymphocyte trafficking [36] have been elucidated. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background Patient derived xenografts (PDXs) for head and neck cancer (HNC) and other cancers represent powerful research platforms. Most groups implant patient tissue into immunodeficient mice immediately although the significance of this time interval is anecdotal. We tested the hypothesis that the time from tumor excision to implantation is crucial for PDX passaging and establishment. Methods We examined whether time or storage medium affected PDX viability for passaging two established HNC PDXs (UW-SCC34, UW-SCC52). Tumors were harvested, stored in ice-cold media or saline for 0–48 hours, and implanted into new mice. Tumor growth was compared by two-way ANOVA with respect to time and storage condition. Three new HNC PDXs (UW-SCC63-65) were generated by implanting patient tissue into mice immediately (Time 0) and 24 hours after receiving tissue from the operating room. Results Similar quantities of tumor were implanted into each mouse. At the end of the experiment, no significant difference was seen in mean tumor weight between the media and saline storage conditions for UW-SCC34 or UW-SCC52 (p = 0.650 and p = 0.177, respectively). No difference in tumor formation prevalence was seen on the basis of time from harvest to implantation (≥13 of 16 tumors grew at every time point). Histological analysis showed strong similarity to the initial tumor across all groups. Tumors developed at both Time 0 and 24 hours for UW-SCC63 and UW-SCC64. Conclusions We demonstrated that neither storage medium nor time from tumor excision to implantation (up to 48 hours) affected viability or histological differentiation in a subsequent passage for two HNC PDXs. Moreover, we revealed that fresh patient tissue is viable up to 24 hours post-resection. This information is important as it applies to the development and sharing of PDXs.
    PLoS ONE 06/2014; 9(6):e100995. DOI:10.1371/journal.pone.0100995 · 3.23 Impact Factor
  • Source
    • "Therefore, it is highly desirable to discover and characterize more effective therapeutic targets for pancreatic cancer treatment. The oncogene KRAS plays an essential role in the progression of pancreatic cancer [9] [10]. In our previous studies , two stable transfected cell lines (P-M and P-W) were constructed through lentivirus-mediated short hairpin RNA (shRNA) targeting of the KRAS gene in PANC-1 cells, enabling us to investigate the cellular response to KRAS knockdown [11]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Pancreatic cancer remains a major unsolved health problem lacking a potent therapeutic option. Our previous studies showed that the ribosomal protein L39 (RPL39) gene was up-regulated after long-term silencing of oncogenic KRAS in pancreatic cancer PANC-1 cells, which indicated that RPL39 may be important for pancreatic cancer development and survival. In the current study, small interfering RNA (siRNA) targeting of the RPL39 gene was performed to determine the effects of the RPL39 gene on growth of pancreatic cancer PANC-1 and BxPC-3 cells in vitro and in vivo. Results from in vitro experiments showed that knockdown of RPL39 expression with RPL39-siRNA suppressed cell proliferation and specifically enhanced cell apoptosis significantly in both PANC-1 and BxPC-3 cells. The increase of caspase-8 activities and the loss of mitochondrial membrane potential after RPL39 silencing indicated that the RPL39 gene may be involved in caspase-8-related mitochondrial apoptosis. Further, treatment with the RPL39-siRNA inhibited the growth of a human pancreatic cancer xenograft in BALB/c nude mice, accompanied by a decreased expression of RPL39. In the xenograft tumors with injection of RPL39-siRNA, the expressions of Ki-67 and CD31 were significantly down-regulated, and apoptosis was markedly induced. Our findings suggested that siRNA against the RPL39 gene may be of value for gene therapy of pancreatic cancer.
    Biotechnology Journal 05/2014; 9(5):652-663. DOI:10.1002/biot.201300321 · 3.49 Impact Factor
  • Source
    • "Because Dicer deletion in this model permits pancreatic development we were able to explore the role of Dicer function in Kras mediated PDA development. Mouse models have revealed that oncogenic Kras can act as a “master regulator” of PDA development, establishing lineages that can give rise to PanINs and PDA and remaining critical for progression[1], [2], [3]. Considerable evidence suggests that acinar cells can give rise to PanINs by undergoing ADM, a process during which acinar cells lose terminal differentiation at the expense of a de-differentiated, duct like state[4], [5], [6], [7]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: miRNA levels are altered in pancreatic ductal adenocarcinoma (PDA), the most common and lethal pancreatic malignancy, and intact miRNA processing is essential for lineage specification during pancreatic development. However, the role of miRNA processing in PDA has not been explored. Here we study the role of miRNA biogenesis in PDA development by deleting the miRNA processing enzyme Dicer in a PDA mouse model driven by oncogenic Kras. We find that loss of Dicer accelerates Kras driven acinar dedifferentiation and acinar to ductal metaplasia (ADM), a process that has been shown to precede and promote the specification of PDA precursors. However, unconstrained ADM also displays high levels of apoptosis. Dicer loss does not accelerate development of Kras driven PDA precursors or PDA, but surprisingly, we observe that mouse PDA can develop without Dicer, although at the expense of proliferative capacity. Our data suggest that intact miRNA processing is involved in both constraining pro-tumorigenic changes in pancreatic differentiation as well as maintaining viability during PDA initiation.
    PLoS ONE 05/2014; 9(5):e95486. DOI:10.1371/journal.pone.0095486 · 3.23 Impact Factor
Show more