Indiana University-Purdue University Indianapolis (IUPUI)Neurofibromatosis Type 1 (NF1) is a highly penetrant autosomal dominant
genetic disorder where mutations in the tumor suppressor gene NF1 leads to decreased
neurofibromin. The most debilitating manifestation is the presence of complex multilineage
Schwann cell-derived plexiform neurofibromas (PN). Historically, little clinical
success has been achieved targeting PN through surgery or chemotherapies. I performed
an shRNA library screen of patient-derived Schwann cell lines to identify novel
therapeutic targets to disrupt PN formation and progression. An shRNA library screen of
human kinases and Rho-GTPases was performed in NF1-/- and paired NF1 competent
immortalized Schwann cell lines. Following sequencing, candidates were identified. We
previously developed a novel mouse model of NF1 wherein a neural crest specific Postncre
targeted loxp-flanked Nf1 that replicated the PN found in patients. Additional cohorts
of mice were generated with biallelic deletion of Rac1 (Nf1f/fRac1f/f Postn-Cre+; DKO ).
Mice were aged for 9 months and peripheral nerves were harvested and fixed in formalin.
Peripheral nerve size was measured and tumors were identified through blinded analysis
of hematoxylin and eosin and Masson’s Trichrome (collagen) stained slides. Rho family
members, including RAC1, were identified as candidates through an shRNA library
screen. Genetic disruption of Rac1 in the Schwann cell lineage resulted in the prevention
of tumor formation in DKO mice, as observed by peripheral nerve size and histological
analysis. I observed an average of 14.8 +/- 2.65 tumors per mouse in the Nf1f/f Postnviii
Cre+ cohort compared to 0 tumors in the DKO (p<0.0001). Following an shRNA library
screen, RAC1 was identified as a candidate to modulate PN formation. Biallelic deletion
of Rac1 in vivo prevented PN formation. I demonstrate that a candidate identified in an
shRNA library screen can translate to an biological effect in a mouse model of PN
