P-ERK

Total ERK

Mel888CHL1 WM793

0 10 50 0 10 50 0 10 50 BRAFi(nmol/L)

Supplemental Figure 2: Other surface molecules unaffected

ns

PD-L1

ns

MCSP

DMSO

BRAFi

Supplemental Figure 1: Validation of MAPK pathway inhibition

ns

HLA-DR

*

HLA A,B,C

MFI

Total ERK

P-ERK

WT BRAFi

DTail0 10 50

0 10 50 0 10 50

0 10 50(nmol/L)

Y320A

Supplemental Figure 3. Phospho-ERK expression levels following inhibition treatment

Transduced Mel888 cells

S335A BRAFi(nmol/L)

P-ERK

Total ERK

***

***

ns

ns

HL

A-A

2 s

urf

ac

e e

xp

res

sio

n

(MF

I)

Supplemental Figure 4:HLA-A2 surface expression

following treatment with MEKi

HLA-A2 variants

DTail

WT

S335A

Y320A

DMSO

MEKi

DMSO MEKi

WM793

Supplemental Figure 6. Intracellular IFN- g (DTail and Y320A)

IFN

-g p

os

itiv

e T

ce

lls

(%

o

f C

D8

)

HLA-A2 (DTail)

HLA-A2 (Y320A)

Mel888 WM793

Supplemental Figure 5. MART-1 TIL recognition of peptide-pulsed T2 cells

ns ns

0 4 8 12 48362418

MART-1

b-actin

Supplemental Figure 7. MART-1 protein expression levels following treatment with

BRAFi over 48hrs

Mel888

Hrs. post-BRAFi treatment

Supplemental Figure 8. Mel888 35S pulse-chase time course and MHC-I IP

BRAFi

DMSO

MEKi

DMSO

1 242 4 128 Hrs. post 35S-Met labeling

Mel888

1 242 4 128

0.70.6

0.80.91.01.1

MART-1Relative Density