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Carlos Baliñas



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    MA17 - Molecular Mechanisms and Therapies (ID 143)

    • Event: WCLC 2019
    • Type: Mini Oral Session
    • Track: Biology
    • Presentations: 1
    • Now Available
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      MA17.06 - Plakophilin 1 Enhances MYC Expression, Promoting Squamous Cell Lung Cancer (Now Available) (ID 823)

      15:45 - 17:15  |  Author(s): Carlos Baliñas

      • Abstract
      • Presentation
      • Slides

      Background

      Plakophilin 1 (PKP1) is a member of the arm-repeat (armadillo) and plakophilin gene families, being an important component of the desmosome. Although desmosomes loss-of-function has been associated with increased cell migration and pro-oncogenic activity, we have observed consistent PKP1 overexpression in patient samples of squamous cell lung cancer (SqCLC) in comparison with lung adenocarcinoma (LUAD) and non-tumoral controls from two datasets achieved by our group, and also from three additional independent datasets.

      Method

      In order to explore this paradox, we developed in vitro and in vivo PKP1 gain/loss functional models in SqCLC cell lines and also we challenged our hypothesis in some LUAD cell lines.

      Result

      Greater cell dissemination but reduced cell proliferation was observed in CRISPR-Cas9 induced, PKP1-knockout clones. Furthermore, PKP1 expression promoted cell proliferation, cell survival, and in vivo xenograft engraftment.

      Interestingly, we demonstrated through several functional experiments (chromatin immunoprecipitation, RNA immunoprecipitation, direct mutagenesis combined with luciferase assays, Western blot, qPCR... among others), and in 7 cell lines from different lung cancer subtypes (5 SqCLC and 2 LUAD cell lines), and different contexts (with and without PKP1 basal expression in order to set up gain and loss expression assays), that these pro-oncogenic activities were mediated by the functional direct relationship between PKP1 and the oncogene MYC. Specifically, PKP1 enhances MYC translation, and MYC increases PKP1 transcription, linking both proteins in a positive feedforward loop.

      Conclusion

      These observations provide a new molecular mechanism of cancer development, revealing PKP1 as a novel oncogene in SqCLC, and as an effective post-transcriptional regulator of MYC, which has been described as overexpressed in around 70% of NSCLC tumors.

      Moreover, PKP1 unveiled as a valuable diagnostic biomarker and a potential therapeutic target for SqCLC. Importantly, PKP1 inhibition may open up the possibility of indirectly targeting MYC, not only in NSCLC (where, as mentioned before, is frequently overexpressed), but also in other tumors. This is of particular interest, because MYC is an oncogene that is dysregulated in most human cancers and is acknowledged as a “most wanted” target for cancer therapy.

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