RAC1

Overview

RAC1 is a Rho-family GTPase involved in actin cytoskeleton organization, cell migration, and proliferation signaling. The RAC1 P29S hotspot mutation is one of the most common recurrent driver mutations in melanoma, arising from UV-induced C>T transitions at a dipyrimidine context and activating RAC1-driven proliferative signaling.

Alterations observed in the corpus

  • RAC1 P29L hotspot mutation found in a melanocyte from a tanning cohort donor in a study of molecular effects of indoor tanning; this variant is a known melanoma driver at the P29 hotspot PMID:38895302.
  • Significantly mutated in melanoma WES cohort (121 tumors); RAC1 P29S was identified as a recurrent hotspot mutation driven by UV-signature mutagenesis PMID:22817889
  • Recurrent RAC1 P29S hotspot mutation identified in melanoma WES cohort (147 tumors, Yale); among significantly mutated genes in melanoma PMID:22842228
  • RAC1 activation is driven by recurrent mutations in upstream regulators ELMO1, DOCK2, TRIO, TIAM1, VAV2, and ECT2 in esophageal adenocarcinoma (EAC), with downstream effector PAK1 recurrently amplified at 11q13; RAC1 itself is not directly mutated PMID:23525077
  • RAC1 P29S recurrent gain-of-function mutation found in 3/14 pre-treatment melanoma tumors of early-resistance patients (P=0.026); associated with early resistance to RAF inhibitors PMID:24265153
  • RAC1 P29S hotspot mutation identified in cutaneous squamous cell carcinoma (cSCC), at the same residue as reported in melanoma PMID:25303977
  • In cutaneous melanoma (SKCM), RAC1 is a UV-signature hot-spot significantly mutated gene occurring in 6.9% of cases; previously linked to BRAF-inhibitor resistance (Van Allen et al., 2014; Watson et al., 2014). PMID:26091043
  • P29S hotspot in 2 desmoplastic melanoma tumors. PMID:26343386
  • RAC1 Q61R mutation in one prostate tumor; paralogous to RAS Q61 hotspot PMID:26544944
  • RAC1 novel hotspot mutations at codons 12, 34, and 61 (G12V/R, P34R, Q61R/K) identified in ~5% of germ cell tumors — highest reported incidence across cancer types in TCGA at time of publication; functionally validated to activate PAK1 and MEK1/2 phosphorylation PMID:27646943.

Cancer types (linked)

  • Melanoma (MEL) — RAC1 P29L identified as a pathogenic driver mutation in a melanocyte clonal expansion study, consistent with UV-induced mutagenesis in tanning-exposed individuals PMID:38895302.

Co-occurrence and mutual exclusivity

  • RAC1 P29L was identified in the tanning cohort alongside other UV-driven driver mutations (BRAF L597R, BRAF G466R, NF1 multiple LOF) across different donor melanocytes, reflecting field cancerization PMID:38895302.

Therapeutic relevance

  • RAC1-mutant melanomas are typically BRAF/NRAS wild-type and thus resistant to BRAF/MEK inhibitors; targeted therapies directed at RAC1 or downstream effectors are under investigation.

Open questions

  • Whether indoor tanning preferentially expands RAC1 P29-mutant clones relative to BRAF-mutant clones, and the relative risk contributions of each driver mutation type to melanoma development in tanning-exposed individuals PMID:38895302.

Sources

This page was processed by crosslinker on 2026-05-14. - PMID:22817889

This page was processed by crosslinker on 2026-05-14. - PMID:22842228

This page was processed by crosslinker on 2026-05-14. - PMID:23525077

This page was processed by crosslinker on 2026-05-14. - PMID:24265153

This page was processed by crosslinker on 2026-05-14. - PMID:25303977

This page was processed by crosslinker on 2026-05-14. - PMID:26091043

This page was processed by crosslinker on 2026-05-14. - PMID:26343386

This page was processed by crosslinker on 2026-05-14. - PMID:26544944

This page was processed by crosslinker on 2026-05-14. - PMID:27646943

This page was processed by entity-page-writer on 2026-05-15.