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\title{Concurrence of a Kinase-dead BRAF and an Oncogenic KRAS Gain-of-function
Mutation in Juvenile Xanthogranuloma}



\author[1]{Markus Seidel}%
\author[2]{Luka Brčić}%
\author[2]{Gerald Hoefler}%
\author[3]{Caroline Hutter}%
\author[3]{Milen Minkov}%
\author[1]{Laura Sophie Steffen}%
\author[1]{Armin Zebisch}%
\author[1]{Martin Benesch}%
\affil[1]{Medizinische Universitat Graz}%
\affil[2]{Medizinische Universitat Graz Institut fur Pathologie}%
\affil[3]{International LCH Study Reference Center CCRI St Anna Kinderkrebsforschung Medical University of Vienna Austria}%


\vspace{-1em}



  
  \date{May 24, 2024}


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\textbf{Concurrence of a Kinase-dead \emph{BRAF} and an
Oncogenic\emph{KRAS} Gain-of-function Mutation in Juvenile
Xanthogranuloma}

\textbf{Markus G. Seidel\textsuperscript{1,2,9}, Luka
Brcic\textsuperscript{3}, Gerald Hoefler\textsuperscript{3}, Caroline
Hutter\textsuperscript{4, 5}, Milen Minkov\textsuperscript{4, 6}, Laura
Sophie Steffen\textsuperscript{1}, Armin Zebisch\textsuperscript{7, 8,
9}, Martin Benesch\textsuperscript{1}}

\textsuperscript{1}Division of Pediatric Hematology-Oncology, Department
of Pediatrics and Adolescent Medicine, Medical University of Graz, Graz,
Austria

\textsuperscript{2}Research Unit for Pediatric Hematology and
Immunology, Medical University of Graz, Graz, Austria

\textsuperscript{3}Diagnostic and Research Institute of Pathology,
Medical University of Graz, Graz, Austria

\textsuperscript{4}International LCH Study Reference Center, CCRI, St.
Anna Kinderkrebsforschung, Medical University of Vienna, Austria

\textsuperscript{5}St. Anna Children's Hospital, Medical University of
Vienna, Austria

\textsuperscript{6}Medical Faculty, Sigmund Freud Private University,
Vienna, Austria

\textsuperscript{7}Division of Hematology, Medical University of Graz,
Graz, Austria

\textsuperscript{8}Otto-Loewi-Research Center for Vascular Biology,
Immunology and Inflammation, Division of Pharmacology, Medical
University of Graz, Graz, Austria

\textsuperscript{9}\emph{Correspondence:} \textbf{Markus G Seidel} , MD,
Division of Pediatric Hematology-Oncology, Department of Pediatrics and
Adolescent Medicine, Auenbruggerplatz 38, Medical University of Graz,
A-8036 Graz, Austria; e-mail: markus.seidel@medunigraz.at ;\textbf{Armin
Zebisch} , MD, Division of Hematology, Medical University of Graz, Graz,
Austria Auenbruggerplatz 38, A-8036 Graz, Austria; e-mail:
armin.zebisch@medunigraz.at .

\emph{Word count:} 536

\emph{Key words:} BRAF; KRAS; juvenile xanthogranuloma (JXG);
vemurafenib; MAPK/ERK signaling pathway; Langerhans cell histiocytosis
(LCH).

\textbf{To the Editor}

Juvenile xanthogranuloma (JXG) is a very rare benign tumor of
histiocytic origin. Being derived from CD14+ dermal dendrocytes, JXG
represents the most common type of non-Langerhans cell histiocytosis
(non-LCH) and typically affects young infants\textsuperscript{1,2}.
Although it is usually confined to solitary, or rarely multiple,
yellow-reddish papulous lesions of the skin (monosystemic) that tend to
regress spontaneously over the course of a few years, JXG may also
extend to ocular, visceral, and central nervous system
(multisystem/systemic) disease\textsuperscript{2}. Cutaneous lesions
generally heal without or sometimes with atrophic scarring, whereas
ocular or visceral involvement may result in severe, even
life-threatening morbidity and require systemic treatment, historically
consisting of agents used in the therapy of LCH (prednisolone, vinca
alkaloids, 6-mercaptopurine, cytarabine, cladribine; \emph{see
also}LCH-IV protocol of the Histiocyte Society at
www.histiocytesociety.org,\emph{ClinicalTrials} identifier:
NCT02205762)\textsuperscript{2-5}. In analogy to LCH and other non-LCH
diseases, recent studies have confirmed the presence of activating
mutations in the MAPK signaling pathways in many cases of systemic JXG,
or rarely, kinase fusions involving BRAF, ALK, or NTRK in various
non-LCH lesions\textsuperscript{6,7}. Vemurafenib has been shown to be
effective in achieving clinical remissions in refractory multisystem
\emph{BRAF} p.V600E-mutated LCH\textsuperscript{8}. Consequently, also
patients with severe systemic JXG may be offered an effective targeted
therapy in the future.

We report on a female infant with multiple cutaneous lesions of JXG
affecting her face, upper trunk and proximal upper extremities. A
concurrence of a \emph{BRAF} p.D594N and a \emph{KRAS} p.G12V mutation
with identical allele frequencies of 12-13\% was detected in these
lesions. The same constellation of both \emph{BRAF} loss-of-function
and\emph{KRAS} gain-of-function mutations occurring simultaneously has
been experimentally explained by a mechanism of oncogenic RAS-dependent
CRAF binding of BRAF and paradoxical activation of the MAPK pathway via
CRAF in the presence of kinase-dead (class III) variants of BRAF or
pharmacological inhibition of BRAF \emph{in vitro} and \emph{in
vivo\textsuperscript{9,10}} . In line, patients treated with BRAF
inhibitors are at risk to develop RAS-mutated keratoacanthomas or
squamous cell carcinomas\textsuperscript{11}, and class III BRAF
mutations were detected in melanoma, colorectal carcinoma, and non-small
cell lung cancer and are typically linked to oncogenic RAS mutations,
NF1 deletions, or increased receptor tyrosine kinase signaling
(\emph{reviewed in} \textsuperscript{12-15}); whereby the exact sequence
of these events remains to be elucidated.

The child is clinically stable and neither eyes, nor visceral organs or
the CNS are affected as determined by imaging and ophthalmological
studies. To date, she is 30 months of age and has been observed without
therapy for one year with a mild ``waxing and waning'' course of the
skin lesions. In contrast, three other children diagnosed with unifocal
cutaneous JXG within the same year at our institution, did not show any
alteration of the genes analyzed (sequencing panel includes \emph{BRAF,
GNA11, GNAQ, HRAS, KRAS, RAC1, CDKN2A, KIT, MAP2K1, PIK3CA, PTEN} ).
This finding and the presence of \emph{MAP2K1} besides \emph{BRAF}
p.V600E mutations in a substantial proportion of current local LCH
patients analyzed with the same panel (MAP2K1 p.F53\_Q58delinsL, n=2;
BRAF V600E n=4; total LCH patients analyzed n= 12) highlight the need
for detailed tumor genotyping and awareness of the affected stage within
the altered signaling pathway prior to initiation of kinase-directed
treatment in histiocytosis to identify the precise target and avoid
unnecessary adverse effects.

\textbf{Conflict of interest}

The authors declare that the research was conducted in the absence of
any commercial or financial relationships that could be construed as a
potential conflict of interest.

\textbf{Funding}

MGS was in part funded by the Steirische Kinderkrebshilfe (Styrian
Children's Cancer Aid).

\textbf{References}

1. Weitzman S, Jaffe R. Uncommon histiocytic disorders: the
non-Langerhans cell histiocytoses. \emph{Pediatr Blood Cancer} .
2005;45(3):256-264.

2. B\selectlanguage{ngerman}üttgen K, Levy M. Juvenile Xanthogranuloma (JXG). In: Corona R ed.
UpToDate ®. Waltham, MA: UpToDate, Wolters Kluwer; 2021.

3. Rajendra B, Duncan A, Parslew R, Pizer BL. Successful treatment of
central nervous system juvenile xanthogranulomatosis with
cladribine.\emph{Pediatr Blood Cancer} . 2009;52(3):413-415.

4. Maintz L, Wenzel J, Irnich M, Reinhard H, Bieber T. Successful
treatment of systemic juvenile xanthogranulomatosis with cytarabine and
2-chlorodeoxyadenosine: case report and review of the
literature.\emph{Br J Dermatol} . 2017;176(2):481-487.

5. Histiocyte\_Society, Histiocytosis NACf, Minkov M. ClinicalTrials.gov
Identifier: NCT02205762: LCH-IV, International Collaborative Treatment
Protocol for Children and Adolescents With Langerhans Cell
Histiocytosis. ClinicalTrialsgov. Vol. 2022 U.S. National Library of
Medicine: National Institutes of Health; 2014.

6. Xu J, Huang X, Wen Y, et al. Systemic Juvenile Xanthogranuloma has a
Higher Frequency of ALK Translocations than BRAFV600E Mutations. \emph{J
Am Acad Dermatol} . 2020.

7. Diamond EL, Durham BH, Haroche J, et al. Diverse and Targetable
Kinase Alterations Drive Histiocytic Neoplasms. \emph{Cancer Discov} .
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8. Donadieu J, Larabi IA, Tardieu M, et al. Vemurafenib for Refractory
Multisystem Langerhans Cell Histiocytosis in Children: An International
Observational Study. \emph{J Clin Oncol} . 2019;37(31):2857-2865.

9. Heidorn SJ, Milagre C, Whittaker S, et al. Kinase-dead BRAF and
oncogenic RAS cooperate to drive tumor progression through
CRAF.\emph{Cell} . 2010;140(2):209-221.

10. Yao Z, Yaeger R, Rodrik-Outmezguine VS, et al. Tumours with class 3
BRAF mutants are sensitive to the inhibition of activated
RAS.\emph{Nature} . 2017;548(7666):234-238.

11. Su F, Viros A, Milagre C, et al. RAS mutations in cutaneous
squamous-cell carcinomas in patients treated with BRAF
inhibitors.\emph{N Engl J Med} . 2012;366(3):207-215.

12. Lin Q, Zhang H, Ding H, et al. The association between BRAF mutation
class and clinical features in BRAF-mutant Chinese non-small cell lung
cancer patients. \emph{J Transl Med} . 2019;17(1):298.

13. Sahin IH, Klostergaard J. BRAF Mutations as Actionable Targets: A
Paradigm Shift in the Management of Colorectal Cancer and Novel
Avenues.\emph{JCO Oncol Pract} . 2021;17(12):723-730.

14. Dankner M. Targeted Therapy for Colorectal Cancers With Non-V600
BRAF Mutations: Perspectives for Precision Oncology. \emph{JCO Precis
Oncol} . 2018;2:1-12.

15. Lokhandwala PM, Tseng LH, Rodriguez E, et al. Clinical mutational
profiling and categorization of BRAF mutations in melanomas using next
generation sequencing. \emph{BMC Cancer} . 2019;19(1):665.

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