Global profiling of EGFR gene mutation, amplification, regulation and tissue protein expression in unknown primary carcinomas: to target or not to target?
BACKGROUND
Epidermal growth factor receptor (EGFR) signalling contributes to malignant transformation and survival. We studied molecular predictors of benefit from EGFR-modulating therapies in patients with cancer of unknown primary (CUP).


METHODS
Tumours from paraffin-embedded biopsies of 50 patients with CUP were stained for EGFR protein by immunohistochemistry. Polymerase chain reaction amplification, single-strand conformational polymorphism and direct sequencing were used to study EGFR intron 1 cytosine-adenosine (CA) repeat length as well as exon 18, 19, 21 activating mutations and amplification.


RESULTS
Thirty-seven tumours (74%) expressed EGFR protein but only six (12%) strongly. Regarding intron 1 CA repeat length, we detected five alleles with CA repeat numbers 16-20, allele 16 being the most common (39%). All samples were heterozygous, the commonest genotype consisting of 16/18 dinucleotides (78%). Five samples had three intron 1 alleles and were associated with EGFR overexpression in 40% of cases. There was no evidence of EGFR exon 18, 19, 21 amplification. Two mutations were detected: Exon 21 2508 C > T, a silent nucleotide polymorphism (R836R) and a G > A substitution in sequences flanking exon 19 (IVS19 + 24G > A) resulting in aberrant mRNA splicing. Neither EGFR protein expression nor CA repeat length were prognostic factors for survival.


CONCLUSIONS
Our data depict absence of molecular predictors of benefit from EGFR modulation in patients with CUP. Study of its molecular pathophysiology and targeting other molecular pathways may be warranted instead.
Dova
Leukothea
L
Haematological Laboratory, Molecular Biology Unit, Ioannina University Hospital, Ioannina, Greece.
Pentheroudakis
George
G
Georgiou
Ioannis
I
Malamou-Mitsi
Vassiliki
V
Vartholomatos
George
G
Fountzilas
George
G
Kolaitis
Nikolaos
N
Kitsiou
Evangelia
E
Pavlidis
Nicholas
N
D000368:Aged; D000369:Aged, 80 and over; D001483:Base Sequence; D017931:DNA Primers; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D020869:Gene Expression Profiling; D018773:Genes, erbB-1; D006801:Humans; D007150:Immunohistochemistry; D007438:Introns; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics*; D009382:Neoplasms, Unknown Primary / Q000235:genetics*; D016133:Polymerase Chain Reaction
D017931:DNA Primers; D004273:DNA, Neoplasm; D009363:Neoplasm Proteins