Virtual Library

 x 
My Library Virtual Library FAQ

Start Your Search

Alissa Poteete



Author of

  • +

    MA17 - Molecular Mechanisms and Therapies (ID 143)

    • Event: WCLC 2019
    • Type: Mini Oral Session
    • Track: Biology
    • Presentations: 1
    • Now Available
    • +

      MA17.10 - Lactate Transporter Blockade as a Strategy to Overcome VEGF Inhibitor-Resistance in LKB1-Deficient NSCLC (Now Available) (ID 2647)

      15:45 - 17:15  |  Author(s): Alissa Poteete

      • Abstract
      • Presentation
      • Slides

      Background

      STK11/LKB1 alterations are found in 20-30% of NSCLC and used to co-occur with KRAS mutations. Because LKB1 activates AMPK, many of the best known functions of LKB1 are attributed to its ability to control metabolic alterations in cells. Our laboratory have previously reported that loss of LKB1 promotes enhanced glycolysis and elevated lactate production and more recently we demonstrated that STK11/LKB1 mutations are the strongest predictors of de novo resistance to immunotherapy in NSCLC. Prior studies have revealed an association between alterations in the LKB1/AMPK pathway and worse clinical outcomes in NSCLC and in patients treated with chemotherapy and bevacizumab. Given the roles of LKB1 in the regulation of cell metabolism and resistance to immunotherapy, it is feasible that LKB1 also impacts on the response to anti-angiogenic therapies.

      Method

      Xenograft mouse models were established by subcutaneous injection of H460 cells (LKB1-deficient) and H460 LKB1-expressing in nude mice and LKR10 (KRASG12D) LKB1 wild-type (K) or LKB1- knockout (KL) into 129Svmice. Mice were randomized to vehicle or B20-4.1.1 anti-VEGF antibody. Glycolytic activity of LKB1-intact and -deficient NSCLC cells was measured by Seahorse assay. We analyzed gene expression of SLC16A3 (MCT4) by qPCR and Western blot. Genetic disruption of MCT4 in the K and KL cell lines was done using CRISPR-Cas9 and mouse models were established by subcutaneous injection into mice.

      Result

      Mice bearing LKB1-expressing H460 xenografts treated with anti-VEGF antibody showed a significant decrease in tumor volume (p<0.05) compared with their vehicle-treated counterparts. However, mice bearing LKB1-deficient H460 xenografts showed markedly reduced efficacy of anti-VEGF therapy compared with that in LKB1-expressing xenografts. Anti-VEGF therapy significantly reduced growth of LKR10 K tumors (p<0.001) but not in LKR10 KL tumors. Microvascular density was not increased in KL tumors following anti-VEGF treatment compared to K. Human isogenic LKB1-deficient cells showed a significantly increased rate of glycolysis and lactate secretion compared with cells expressing LKB1. Human and murine LKB1-deficient cells also had increased MCT4 expression compared to K cells. Immunofluorescence and RPPA analysis of tumor samples from the K and KL mouse models showed that KL tumors upregulated MCT4 protein expression compared with K tumors (p<0.0001). The genetic disruption of MCT4 KL tumors significantly improved tumor volume reduction to anti-VEGF therapies in vivo (p<0.001).

      Conclusion

      LKB1 loss is associated with increased lactate secretion and resistance to VEGF inhibition in NSCLC. The targeting of the lactate transporter MCT4 enhance the sensitivity of LKB1-deficient NSCLC to anti-VEGF therapy.

      Only Members that have purchased this event or have registered via an access code will be able to view this content. To view this presentation, please login, select "Add to Cart" and proceed to checkout. If you would like to become a member of IASLC, please click here.

      Only Active Members that have purchased this event or have registered via an access code will be able to view this content. To view this presentation, please login or select "Add to Cart" and proceed to checkout.

  • +

    P1.14 - Targeted Therapy (ID 182)

    • Event: WCLC 2019
    • Type: Poster Viewing in the Exhibit Hall
    • Track: Targeted Therapy
    • Presentations: 1
    • Moderators:
    • Coordinates: 9/08/2019, 09:45 - 18:00, Exhibit Hall
    • +

      P1.14-08 - Activity of Poziotinib and Other 2nd-Gen Quinazoline EGFR TKIs in Atypical Exon18 and Acquired Osimertinib Resistance Mutants (ID 2694)

      09:45 - 18:00  |  Author(s): Alissa Poteete

      • Abstract

      Background

      In EGFR, exon 18 encodes for the P-loop (L718-V726), and mutations in this region (G719S/A, L718Q/V, G724S) are known to reduce sensitivity to osimertinib and first-generation EGFR TKIs. Osimertinib resistance is associated with a number of acquired mutations in exons 19 and 20 (S784F, L747S, C797S and L792H). We investigated the frequency and drug sensitivity of these and other osimertinib-resistant EGFR mutations

      Method

      We generated ~50 different Ba/F3 cell line models expressing classical and/or atypical EGFR mutations (exons 18-21) and evaluated the transforming ability and sensitivity to 14 EGFR TKIs including non-covalent (first-generation), afatinib, dacomitinib, and poziotinib (quinazoline and covalent, second-generation), and covalent T790M-specific (third-generation) inhibitors. Impact of atypical mutations was analyzed by in silico modeling.

      Result

      We found 3.6% (N=32/895) of EGFR-mutant patients had atypical, exon 18, P-loop mutations in the MD Anderson GEMINI database. Modeling of classical EGFR mutations revealed osimertinib has distinct interactions between the solvent front of osimertinib and residues within the P-loop of EGFR, whereas second-generation quinazoline TKIs, such as poziotinib, extend into the pocket, near T790, lacking these interactions. Mutations in the P-loop were predicted to shift osimertinib out of alignment with V726 and F723, causing resistance to osimertinib but not quinazoline-based TKIs. Atypical exon 18 mutations (G719S/A, L718Q/V, G724S) had IC50 values of 113.6nM, 1.6nM, and 137.5nM for first-, second-, and third-generation TKIs, respectively. Second-generation TKIs inhibited G719S/A-T790M mutations at concentrations 2-fold lower than third-generation TKIs (IC50 = 23.4nM and 46nM). Osimertinib-resistance mutations (L747S, S784F, C797S, L792H) co-occurring with classical sensitizing mutations (L858R or ex19del) had IC50 values of 56.8nM, 1.4nM, and 996nM to first, second and third-generation inhibitors. Of the second-generation TKIs tested, poziotinib was the most potent for atypical exon 18 P-loop mutations; G719S/A-T790M mutations; and classical mutants with acquired osimertinib-resistance mutations (IC50= 0.4nM, 3.2nM, 0.8nM).

      Conclusion

      Exon 18 atypical P-loop mutations and osimertinib-resistance mutations demonstrated high sensitivity to second-generation quinazoline TKIs, compared to first- and third-generation inhibitors. Mutations in the P-loop of EGFR confer resistance to third-generation TKIs by destabilizing solvent front interactions of the molecule, and osimertinib-resistance mutations interfere with covalent binding at C797. Second-generation TKIs, especially poziotinib, are potent inhibitors of these mutations because they have increased hydrophobic interactions at the back of the drug binding cleft that are retained without covalent binding. Together, these data indicate that poziotinib and other second-generation TKIs may be useful for the treatment of NSCLC patients with atypical P-loop and selected osimertinib-resistant EGFR mutations.