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Tumor Discovery Somatic mutations in POLE and POLD1 in colorectal cancer

3.2. Clinicopathological and molecular significance Table 3. Clinicopathological and molecular features of
of POLE/POLD1-mutations in CRC POLE/POLD1‑mutated colorectal cancer
There was no significant association or correlation between Features POLE/POLD1‑ POLE/POLD1‑ P‑value
POLE/POLD1 variants and any of the clinicopathological wild type mutant
and molecular features examined (Table 3). However, 90% Age 69.73 (±1.26) 63.22 (±3.94) 0.093
of the POLE/POLD1-mutated tumors were microsatellite years years
stable, and 80% of them were also aneuploid. This lack of Gender
association was observed irrespective of whether POLE Male 45 5 0.731
and POLD1 were analyzed separately or together.
Female 28 4
3.3. Functional effects of POLE and POLD1 variants Anatomical sites
The possible effects of the POLE and POLD1 variants on the Colon 50 8 0.271
proofreading activities of the enzymes were tested in silico Rectum 23 1
using the PROVEAN batch protein and the PON-P2 Tumor size 4.78 (±0.23) cm 6.67 (±1.33) cm 0.199
protein prediction tools. The results showed that whereas Tumor grade
both variants identified in POLD1 could confer possible Low grade 1 0 1.000
“deleterious,” “damaging,” and “pathogenic” effects on the
protein by all of PROVEAN, SIFT, and PON-P2 predictions, High grade 70 9
respectively, four of the POLE variants (L455Q, T278M, Tumor stage
L432P, and D414N) were predicted to be deleterious/ T2 and earlier 10 0 0.592
damaging/pathogenic by all three prediction tools, one T3 and later 62 9
(A374V) was scored neutral/tolerated by all three, whereas Nodal stage
two (G433D and T457A) were predicted to be damaging
or pathogenic by at least one prediction tool (Table 4). The N0 32 3 0.725
POLE exon 14 codon 461 variant identified gives rise to N1 40 6
a stop codon, which we considered to have a deleterious/ TNM stage
damaging effect on protein translation. In total, nine of the Stages 1 and 2 30 3 0.731
10 POLE/POLD1 variants identified were predicted to alter Stages 3 and 4 42 6
the proofreading activities of the enzymes.
Perineural invasion
4. Discussion Absent 49 6 1.000

Using a combination of QMC-PCR, COLD-PCR, and Sanger Present 21 3
sequencing, 10 non-recurrent variants were detected in the Vascular invasion
endonuclease domains of POLE and POLD1 in 12% of CRC Absent 31 1 0.080
cases. The QMC-PCR demonstrated excellent performance Present 41 9
in amplifying FFPE DNA, which facilitated effective Residual tumor
mutation detection by HRM analyses [16]. The COLD-PCR,
an established method for enriching minor mutant alleles, Absent 67 9 1.000
was also employed. We have also previously utilized Present 4 0
18
COLD-PCR followed by HRM analyses (COLD-HRM) to Duke stage
differentiate between germline and somatic mutations. 23 Stages A and B 32 3 0.724
First, the age of POLE/POLD1-mutant CRC patients Stages C and D 38 6
was significantly lower than that of the wild-type patients, Microsatellite status
indicating a potential association between younger age MSS 68 9 0.549
and these mutations. This finding aligns with previous
studies suggesting that POLE and POLD1 mutations MSI 5 1
are more prevalent in younger CRC patients and may Ploidy status
contribute to early-onset CRC. This observation aligns Aneuploid 37 8 0.137
with prior research indicating a higher prevalence of Diploid 29 2
POLE and POLD1 mutations in younger CRC patients, Abbreviations: MSI: Microsatellite instability; MSS: Microsatellite
implicating them in early-onset CRC. Second, the stable.
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Volume 3 Issue 3 (2024) 6 doi: 10.36922/td.3659