MLH1/PMS2 Expression Could Tell Classical NTRK Fusion in Fluorescence In Situ Hybridization Positive Colorectal Carcinomas

NTRK gene alterations were enriched in hepatoid or enteroblastic differentiation type of gastric cancer

Aims Currently, the clinicopathological characteristics of gastric cancer (GC) with oncogenic NTRK alterations are not well known. Although NTRK fusion has been identified as prevalent in DNA mismatch repair protein deficient (dMMR) colorectal cancer (CRC), the relationship between NTRK alterations and dMMR protein expression in GC has not been previously explored.

METHODS

Our study comprised 51 cases of EBV(Epstein-barr virus)-associated gastric carcinomas, 94 cases of dMMR GC, 90 cases of gastric adenocarcinoma with hepatoid or enteroblastic differentiation (GAHED) and 256 cases of conventional GC. Furthermore, to investigate the connection between NTRK fusion and dMMR proteins, we collected dMMR tumours of various types, including 21 cases of duodenal adenocarcinomas, 46 endometrioid carcinomas and 82 CRCs. NTRK fusion and amplification were screened in GC and various types of dMMR tumours using fluorescence in situ hybridisation (FISH), while cases positive for FISH translocation underwent next-generation sequencing testing.

RESULTS

Our findings revealed the existence of two cases each of NTRK fusions and NTRK amplifications, which were all enriched in case of GAHED. Additionally, following an analysis of several types of cancers, we discovered that NTRK gene alterations were only present in dMMR CRC.

CONCLUSIONS

Our results indicate that NTRK gene alterations are not enriched in GC with dMMR but are specifically enriched in cases of GAHED.

Feasibility of two-step approach for screening NTRK fusion in two major subtypes of non-small cell lung cancer within a large cohort

Our objective is to investigate a cost-effective approach to screen for NTRK fusion in the major subtypes of non-small cell lung cancer (NSCLC). Evaluate the concordance between immunohistochemistry (IHC) and next-generation sequencing (NGS), as well as between fluorescence in situ hybridization (FISH) and NGS, to detect any discrepancies in methodological consistency between lung adenocarcinoma (LADC) and lung squamous cell carcinoma (LSCC). Analyze the factors influencing IHC results. A cohort of 1654 patients with NSCLC underwent screening for NTRK fusion using whole slide IHC. The positive cases were analyzed by both FISH and NGS. Totally, 57 tested positive for pan-TRK, with positivity rates of 0.68% (10/1467) for LADC and 29.01% (47/162) for LSCC. FISH showed separate NTRK1 and NTRK3 rearrangements in two pan-TRK-positive LADCs, while all LSCCs tested negative. NGS confirmed functional NTRK fusion in two FISH-positive cases: one involving TPM3-NTRK1 and the other involving SQSTM1-NTRK3. A non-functional fusion of NTRK2-XRCC1 was detected in LSCC, while FISH was negative. According to our approach, the prevalence of NTRK fusion in NSCLC is 0.12%. The concordance rate between IHC and RNA-based NGS was 20% (2/10) in LADC and 0% (0/162) in LSCC. When the positive criteria increased over 50% of tumor cells showing strong staining, the concordance would be 100% (2/2). A concordance rate of 100% (2/2) was observed between FISH and RNA-based NGS in LADC. The expression of pan-TRK was significantly correlated with the tumor proportion score (TPS) of PD-L1 (p < 0.05) and transcript per million (TPM) values of NTRK2 (p < 0.05). We recommend using IHC with strict criteria to screen NTRK fusion in LADC rather than LSCC, confirmed by RNA-based NGS directly. When the NGS results are inconclusive, FISH validation is necessary.

HER2 overexpression/amplification status in colorectal cancer: a comparison between immunohistochemistry and fluorescence in situ hybridization using five different immunohistochemical scoring criteria

OBJECTIVE

Although HER2 has gradually become an important therapeutic target for colorectal cancer (CRC), a unified and standard HER2 scoring system was still not established in CRC, and the debatable results of immunohistochemistry and fluorescence in situ hybridization (FISH) in CRC requires further exploration.

METHODS

In this study, we use five immunohistochemical (IHC) scoring criteria (i.e., IRS-p, IRS-m, GEA-s, GEA-b and HERACLES) and two FISH criteria to evaluate HER2 status, and further evaluate the correlation between HER2 status and clinicopathological features, survival in a large, unselected Chinese cohort of 664 CRCs.

RESULTS

Finally, we set HER2/CEP17 ratio ≥ 2.0, or an average HER2 copy number ≥ 6.0 as FISH-positive threshold and the amplification rate of HER2 gene was 7.08% (47/664).The HER2 positivity (IHC 3+) was 2.71%, 3.16%, 2.56%, 2.71% and 3.16%, according to the IHC scoring criteria of IRS-p, IRS-m, GEA-s, GEA-b and HERACLES, respectively. Set FISH results as the golden standard; receiver-operating characteristic analysis showed that IRS-p had both high sensitivity and specificity than other IHC scoring systems to evaluate HER2 status. Based on IRS-p criterion, There were significant differences in tumor differentiation (p = 0.038), lymphatic vascular invasion (p = 0.001), pN stage (p value = 0.043), and overall survival (p < 0.001) among IHC score 0-3 + groups. Meanwhile, there were significant differences in pT stage (p = 0.031), pN stage (p = 0.009) and overall survival (p < 0.001) among FISH subgroups.

CONCLUSION

The IRS-p criterion was more suitable for assessing the HER2 status in CRC patients than other IHC criteria. Whereas for FISH scoring system, only HER2/CEP17 < 2.0, meanwhile HER2cn < 4.0 and HER2cn ≥ 6.0 were subgroups with unique clinicopathological characteristics.

Pan-tropomyosin receptor kinase immunohistochemistry is a feasible routine screening strategy for NTRK fusions in mismatch repair-deficient colorectal carcinomas

We have previously revealed the high enrichment of NTRK fusion in mismatch repair deficient (dMMR) CRCs. Optimized diagnostic approaches are urgently needed to identify dMMR CRCs that could benefit from TRK inhibitor therapy. A consecutive cohort of 240 surgically resected dMMR CRCs from 2015 to 2021 was collected for pan-TRK immunohistochemistry (IHC) using pan-TRK clone EPR17341 (VENTANA). We analyzed the sensitivity and specificity of pan-TRK IHC with sequential DNA/RNA-based Next Generation Sequencing (NGS) as the reference method and further explored IHC staining patterns and their correlation with fusion variants in dMMR CRCs. Of 240 dMMR CRCs, 15 (6.2%) were stained positive for pan-TRK IHC, and the sensitivity and specificity were both 100%. Five staining patterns were revealed, which correlated with fusion variants. Diffuse and strong positivity in membrane and cytoplasm were detected in all 6 cases with TPM3-NTRK1 fusions (6/15, 40%). Weak granular cytoplasmic staining, including diffuse or focal positivity, was found in 6 NTRK3 fusions (3 ETV6-NTRK3 and 3 EML4-NTRK3) (6/15, 40%). Diffuse and strong nuclear positivity was noticed in 2 LMNA-NTRK1 fusions (2/15, 13.3%). Intense granular cytoplasmic staining was observed in the only case with PLEKHA6-NTRK1 fusion (1/15, 6.7%). Interestingly, pan-TRK positivity was observed in one case with precursor lesions in both precancerous and cancerous regions, whereas MLH1 loss was restricted to the cancerous region. In summary, an optimized multi-step algorithm using pan-TRK IHC as a screening method was proposed to identify CRC patients harboring NTRK fusions.

The sensitivity of pan-TRK immunohistochemistry in solid tumours: A meta-analysis

INTRODUCTION

Since the approval of neurotrophic tropomyosin receptor kinase (NTRK) tyrosine kinase inhibitors for fist-line advanced stage pan-cancer therapy, pathologists and molecular biologists have been facing a complex question: how should the large volume of specimens be screened for NTRK fusions? Immunohistochemistry is fast and cheap, but the sensitivity compared to RNA NGS is unclear.

METHODS

We performed RNA-based next-generation sequencing on 1,329 cases and stained 24 NTRK-rearranged cases immunohistochemically with pan-TRK (ERP17341). Additionally, we performed a meta-analysis of the literature. After screening 580 studies, 200 additional NTRK-rearranged cases from 13 studies, analysed with sensitive molecular diagnostics as well as pan-TRK IHC, were included.

RESULTS

In the included 224 NTRK-rearranged solid tumours, the sensitivity for pan-TRK IHC was 82% and the false-negative rate was 18%. NTRK3 fusions had more false negatives (27%) compared to NTRK1 (6%) and NTRK2 (14%) (p = 0.0006). Membranous, nuclear and peri-nuclear staining patterns strongly correlated with different fusion products, with membranous staining being more prevalent in NTRK1 and NTRK2, nuclear in NTRK3, and perinuclear in NTRK1.

CONCLUSION

Despite a reduction in the number of molecular analysis, using pan-TRK immunohistochemistry as a prescreening method to detect NTRK fusions in solid tumours will miss 18% of all NTRK-fused cases (especially involving NTRK3). Therefore, the most comprehensive and optimal option to detect NTRK fusions is to perform molecular testing on all eligible cases. However, in case of financial or logistical limitations, an immunohistochemistry-first approach is defensible in tumours with a low prevalence of NTRK fusions.