Splice switching an oncogenic ratio of SmgGDS isoforms as a strategy to diminish malignancy

Anthony C. Brandt, Lisa McNally, Ellen L. Lorimer, Bethany Unger, Olivia J. Koehn, Kiall F. Suazo, Lisa Rein, Aniko Szabo, Shirng Wern Tsaih, Mark D. Distefano, Michael J. Flister, Frank Rigo, Mark T. McNally, Carol L. Williams

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The chaperone protein SmgGDS promotes cell-cycle progression and tumorigenesis in human breast and nonsmall cell lung cancer. Splice variants of SmgGDS, named SmgGDS-607 and SmgGDS-558, facilitate the activation of oncogenic members of the Ras and Rho families of small GTPases through membrane trafficking via regulation of the prenylation pathway. SmgGDS-607 interacts with newly synthesized preprenylated small GTPases, while SmgGDS-558 interacts with prenylated small GTPases. We determined that cancer cells have a high ratio of SmgGDS-607:SmgGDS-558 (607:558 ratio), and this elevated ratio is associated with reduced survival of breast cancer patients. These discoveries suggest that targeting SmgGDS splicing to lower the 607:558 ratio may be an effective strategy to inhibit the malignant phenotype generated by small GTPases. Here we report the development of a splice-switching oligonucleotide, named SSO Ex5, that lowers the 607:558 ratio by altering exon 5 inclusion in SmgGDS pre-mRNA (messenger RNA). Our results indicate that SSO Ex5 suppresses the prenylation of multiple small GTPases in the Ras, Rho, and Rab families and inhibits ERK activity, resulting in endoplasmic reticulum (ER) stress, the unfolded protein response, and ultimately apoptotic cell death in breast and lung cancer cell lines. Furthermore, intraperitoneal (i.p.) delivery of SSO Ex5 in MMTV-PyMT mice redirects SmgGDS splicing in the mammary gland and slows tumorigenesis in this aggressive model of breast cancer. Taken together, our results suggest that the high 607:558 ratio is required for optimal small GTPase prenylation, and validate this innovative approach of targeting SmgGDS splicing to diminish malignancy in breast and lung cancer.

Original languageEnglish (US)
Pages (from-to)3627-3636
Number of pages10
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number7
StatePublished - Feb 18 2020

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS. This work was supported by National Cancer Institute (NCI) R01 CA188871 (to C.L.W.), NCI R01 CA193343 (to M.J.F.), National Institute of General Medical Sciences R01 GM084152 (to M.D.D.), a Medical College of Wisconsin Cancer Center Multi-Principal Investigator Pilot Grant (to M.T.M. and M.J.F.), Kathy Duffey Fogarty Award for Breast Cancer Research KDF-13 (to M.T.M.), Wisconsin Breast Cancer Showhouse BST-15 (to M.T.M.), METAvivor Foundation (M.J.F.), and Mary Kay Foundation Award Grant 024.16 (to M.J.F.). Additional support was provided by the Joan K. Van Deuren Professor in Breast Cancer Research Award (to C.L.W.), Kathleen M. Duffey Fogarty Eminent Scholar in Breast Cancer Research Award (to C.L.W.), and Nancy Laning Sobczak, PhD, Breast Cancer Research Award (to C.L.W.).

Publisher Copyright:
© 2020 National Academy of Sciences. All rights reserved.


  • Alternative splicing
  • Prenylation
  • RAP1GDS1
  • Small GTPases
  • SmgGDS

PubMed: MeSH publication types

  • Journal Article
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't


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