PLK1 and FoxM1 expressions positively correlate in papillary thyroid carcinoma and their combined inhibition results in synergistic anti-tumor effects

Polo-like kinase 1 (PLK1; also known as serine/threonine-protein kinase PLK1) serves as a central player in cell proliferation, exerting critical regulatory roles in mitotic processes and cell survival. We conducted an analysis of PLK1 protein expression in a large cohort of samples from papillary thyroid carcinoma (PTC) patients and examined its functional significance in PTC cell lines, both in vitro and in vivo. PLK1 overexpression was noted in 54.2% of all PTC and was significantly associated with aggressive clinicopathological parameters; it was also found to be an independent prognostic marker for shorter recurrence-free survival. Given the significant association between PLK1 and forkhead box protein M1 (FoxM1), and their concomitant overexpression in a large proportion of PTC samples, we explored their correlation and their combined inhibitions in PTC in vitro and in vivo. Inhibition of PLK1 expression indeed suppressed cell proliferation, leading to cell cycle arrest and apoptosis in PTC cell lines. Significantly, the downregulation of PLK1 reduced the self-renewal capability of spheroids formed from PTC cells. Immunoprecipitation analysis shows that PLK1 binds to FoxM1 and vice versa in vitro. Mechanistically, PLK1 knockdown suppresses FoxM1 expression, whereas inhibition of FoxM1 does not affect PLK1 expression, which suggests that PLK1 acts through the FoxM1 pathway. The combined treatment of a PLK1 inhibitor (volasertib) and a FoxM1 inhibitor (thiostrepton) demonstrated a synergistic effect in reducing PTC cell growth in vitro and delaying tumor growth in vivo. This study highlights the important role of PLK1 in PTC tumorigenesis and prognosis. It also highlights the synergistic therapeutic potential of dual-targeting PLK1 and FoxM1 in PTC, unveiling a potential innovative therapeutic strategy for managing aggressive forms of PTC.

Identification and characterization of ATM founder mutation in BRCA-negative breast cancer patients of Arab ethnicity

Breast cancer (BC) is the most prevalent malignancy among women worldwide with germline pathogenic variants/likely pathogenic variants (PVs/LPVs) in BRCA1/2 accounting for a large portion of hereditary cases. Recently, heterozygous PVs/LPVs in the ATM serine/threonine kinase or Ataxia-telangiectasia mutated gene (ATM) has been identified as a moderate susceptibility factor for BC in diverse ethnicities. However, the prevalence of ATM PVs/LPVs in BC susceptibility in Arab populations remains largely unexplored. This study investigated the prevalence of ATM PVs/LPVs among BC patients from Saudi Arabia, employing capture-sequencing technology for ATM PVs/LPVs screening in a cohort of 715 unselected BC patients without BRCA1/2 PVs/LPVs. In addition, founder mutation analysis was conducted using the PHASE program. In our entire cohort, four unique PVs/LPVs in the ATM gene were identified in six cases (0.8%). Notably, one recurrent LPV, c.6115G > A:p.Glu2039Lys was identified in three cases, for which haplotype analysis confirmed as a novel putative founder mutation traced back to 13 generations on average. This founder mutation accounted for half of all identified mutant cases and 0.4% of total screened cases. This study further reveals a significant correlation between the presence of ATM mutation and family history of BC (p = 0.0127). These findings underscore an approximate 0.8% prevalence of ATM germline PVs/LPVs in Arab BC patients without BRCA1/2 PVs/LPVs and suggest a founder effect of specific recurrent ATM mutation. These insights can help in the design of a genetic testing strategy tailored to the local population in Saudi Arabia, thereby, enabling more accurate clinical management and risk prediction.

PALB2 germline mutations in a large cohort of Middle Eastern breast-ovarian cancer patients

The PALB2 gene is a breast cancer (BC) and ovarian cancer (OC) predisposition gene involved in the homologous recombination repair pathway. However, the prevalence and clinicopathological association of PALB2 pathogenic/likely pathogenic (PV/LPV) variants in Middle East is still not fully explored. Total 918 BC/OC patients from Saudi Arabia were selected for PALB2 mutations screening using capture sequencing technology. Five heterozygous PVs or LPVs were identified in six cases, accounting for 0.65% (6/918) of entire cohort. Two cases (33.3%) harbored PVs and four cases (66.7%) carried LPVs. Four PVs/LPVs (80%) were frameshift along with one novel splicing LPV (c.2835-2_2835-1delinsTT). One recurrent LPV (c.3425delT: p.L1142fs) was identified in two cases. All six affected carriers have breast cancer diagnosis with median age of 39.5 years (range 34-49 years). Only two cases (33%) have documented family history of cancer. Breast cancer phenotype was invasive ductal unilateral cancer in all cases with 66.7% of hormone receptor positive and 16% of triple negative tumors. Germline PVs/LPVs in the PALB2 gene were observed in low frequency of 0.65% in Saudi BC and/or OC. Our study confirms one recurrent LPV and one novel LPV in Saudi breast cancer patients.

Overexpression of the pro-protein convertase furin predicts prognosis and promotes papillary thyroid carcinoma progression and metastasis through RAF/MEK signaling

Furin belongs to the pro-protein convertases (PCs) family and its aberrant expression has been documented in various types of cancers; however, its role in thyroid cancer remains unclear. We investigated the expression of furin in a large cohort of Middle Eastern papillary thyroid carcinoma (PTC) patient samples and explored its functional role and mechanism in PTC cell lines in vitro and in vivo. Furin overexpression was observed in 44.6% of all PTC cases and was significantly associated with aggressive clinicopathological parameters and poor outcomes. We show that the knockdown of FURIN suppresses tumor growth, proliferation, migration, invasion, spheroid growth, and progression of epithelial-to-mesenchymal transition (EMT) in B-Raf proto-oncogene, serine/threonine kinase (BRAF) mutant cells, whereas its overexpression in BRAF wild-type PTC cell lines reversed the effect. FURIN knockdown in the BRAF mutant cell line led to reduced tumor growth and increased apoptosis. Mechanistically, FURIN knockdown led to MEK/ERK pathway suppression in BRAF mutant cells, although inhibition of MEK did not affect furin expression, which suggests that furin acts through the MEK/ERK pathway. Furthermore, our study revealed the synergistic antitumor effect of furin depletion and anti-MEK inhibitor treatment. Overall, these results indicate that furin is an important prognostic marker in Middle Eastern PTC and that it plays a crucial role in BRAF-associated MAP/ERK pathway activation and tumorigenesis. Furin inhibition could be a potential therapeutic target for aggressive PTC.

Lynch Syndrome Identification in Saudi Cohort of Endometrial Cancer Patients Screened by Universal Approach

Lynch syndrome (LS) is the most common cause of inherited endometrial cancer (EC). The prevalence and molecular characteristic of LS in Middle Eastern women with EC have been underexplored. To evaluate the frequency of LS in a cohort of EC patients from Saudi Arabia, a total of 436 EC cases were screened utilizing immunohistochemistry (IHC), MLH1 promoter methylation analysis and next-generation sequencing technology. A total of 53 of 436 (12.2%) ECs were classified as DNA mismatch repair-deficient (dMMR). MLH1 promoter hypermethylation was detected in 30 ECs (6.9%). Three ECs (0.7%) were found to be LS harboring germline pathogenic variants (PVs)/likely pathogenic variants (LPVs): two in the MSH2 gene and one in the MSH6 gene. Three ECs (0.7%) were Lynch-like syndrome (LLS) carrying double somatic MSH2 PVs/LPVs. Seven cases were found to have variants of uncertain significance in cancer-related genes other than MMR genes. Our results indicate that LS prevalence is low among Saudi EC patients and LLS is as common as LS in this ethnicity. Our findings could help in better understanding of the prevalence and mutational spectrum of this syndrome in Saudi Arabia, which may help in defining best strategies for LS identification, prevention and genetic counseling for EC patients.

Abstract 5177: Lymph node ratio is superior to AJCC N stage for predicting recurrence in papillary thyroid carcinoma

Objective: Recently, lymph node ratio (LNR) has emerged as an alternative to American Joint Committee on Cancer (AJCC) N stage, with superior prognostic value. The utility of LNR in Middle Eastern Papillary thyroid carcinoma (PTC) remains unknown. Therefore, we retrospectively analyzed a large cohort of 1407 PTC patients for clinico-pathological associations of LNR.

Methods: Receiver operating characteristics (ROC) curve was used to determine the cut-off for LNR. We also performed multivariate logistic regression analysis to determine whether LNR or AJCC N stage was superior in predicting recurrence in PTC.

Results: Based on ROC curve analysis, a cut-off of 0.15 was chosen for LNR. High LNR was significantly associated with adverse clinico-pathological characteristics such as male sex, extrathyroidal extension, lymphovascular invasion, multifocality, bilateral tumors, T4 tumors, lateral lymph node (N1b) involvement, distant metastasis, advanced tumor stage, ATA high risk category and tumor recurrence. On multivariate analysis, we found that LNR was a better predictor of tumor recurrence than AJCC N stage (Odds ratio: 1.96 vs. 1.30; p value: 0.0184 vs. 0.3831). We also found that LNR combined with TNM stage and ATA risk category improved the prediction of recurrence-free survival, compared to TNM stage or ATA risk category alone.

Conclusions: The present study suggests LNR is an independent predictor of recurrence in Middle Eastern PTC. Integration of LNR with 8th edition AJCC TNM staging system and ATA risk stratification will improve the accuracy to predict recurrence in Middle Eastern PTC and help in tailoring treatment and surveillance strategies in these patients.

Citation Format: Sandeep K. Parvathareddy, Abdul K. Siraj, Zeeshan Qadri, Saeeda O. Ahmed, Nabil Siraj, Felisa DeVera, Padmanaban Annaiyappanaidu, Maria A. Sabido, Wael Haqawi, Hassan Aldossari, Khawla S. Al-Kuraya. Lymph node ratio is superior to AJCC N stage for predicting recurrence in papillary thyroid carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5177.

Tumor size is an independent negative prognostic factor for event free survival in children with differentiated thyroid cancer

BACKGROUND

The incidence of pediatric differentiated thyroid carcinoma (DTC) is increasing. Despite the advanced disease at presentation, the overall prognosis of DTC in children is excellent. The aim of this study is to investigate the risk stratifying factors for event free survival (EFS) of pediatric DTC from Middle Eastern ethnicity.

METHODS

Eighty-eight patients aged ≤18 years with diagnosis of primary DTC were retrospectively analyzed. Cox proportional hazards model were used to calculate Hazard Ratios (HR) and Kaplan-Meier analysis were conducted to investigate EFS.

RESULTS

Eighty-eight (23 males and 65 females) pediatric DTCs who underwent surgery and radioactive iodine therapy had been reported (median age at diagnosis 15 years; range 5.9-17.9), with lymph node metastasis (LNM) noted in 70.5% and distant metastasis in 13.6%. Mean follow-up was 8.4 years. Ten-year overall survival rate was 98.4% while 10-year EFS was 79.2%. EFS was negatively impacted by the presence of LNM, distant metastasis and tumor size >4cm. American Thyroid Association risk stratification did not impact EFS in our cohort. Multivariate analysis revealed tumor size >4cm (HR = 5.34; 95% confidence interval (CI) = 1.36 - 20.22; p = 0.0177) and distant metastasis (HR = 8.73; 95% CI = 1.48 - 60.05; p = 0.0154) as independent negative prognostic factors for EFS.

CONCLUSIONS

Primary tumor size and the presence of distant metastasis at diagnosis are the only independent prognostic risk factors for EFS in pediatric DTC in Middle Eastern ethnicity. Children with tumor size over 4cm had poor EFS, which may justify the need of more aggressive treatment and frequent follow-up.

Abstract 730: Annual hazard rate of recurrence in Middle-Eastern papillary thyroid cancer over a long-term follow-up

Predicting the pattern of recurrence is necessary to establish optimal surveillance and treatment strategies. We identified patient population that remain at risk for an event and clarify changes in the hazard rate (HR) for tumor recurrence overtime in Middle Eastern patients with Papillary Thyroid Cancer (PTC). Data for 1201 PTC patients from single institute with median follow-up of 9.5 years were analyzed. Estimated HR were plotted overtime for the entire cohort, as well as for radioactive iodine (RAI) ablation in patients separately. The changes in risk were further analyzed according to clinical variable and factors predictive of early (≤ 5years) and late (>5 years) recurrence were explored using Cox regression analysis. Tumor recurrence was noted in 18.4% (221/1201) patients. The annualized hazard of PTC recurrence was highest during the first 5 years (2.8%), peaking between 1 - 2 years (3.7%), with a second smaller peak between 13 - 14 years (3.2%). Patients receiving RAI therapy had a lower hazard of recurrence compared to those who did not receive RAI therapy (1.5% vs 2.7%, p = 0.0001). Importantly, this difference was significant even in the intermediate-risk PTC patients (0.7% vs 2.3%; p = 0.0001). Interestingly, PTC patients who were male, aged ≥ 55 years, with lymph node involvement and advanced stage disease were still at high risk for late recurrence. In conclusion, we confirmed the validity of double-peaked time-varying pattern for risk of recurrence in Middle-Eastern PTC patients. Furthermore, according to the time distribution of recurrence hazard, we could formulate individualized treatment and surveillance plans in PTC patients.

Citation Format: Abdul K. Siraj, Sandeep K. Parvathareddy, Zeeshan Qadri, Saud Azam, Felisa De Vera, Maha Al-Rasheed, Wael Haqawi, Hassan AlDossari, Khawla S. Al-Kuraya. Annual hazard rate of recurrence in Middle-Eastern papillary thyroid cancer over a long-term follow-up [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 730.

Abstract 729: Prognostic significance of COX-2 over-expression in BRAF mutated Middle Eastern PTC

The cyclooxygenase-2 (COX-2) - prostaglandin E2 (PGE2) pathway has been implicated in carcinogenesis with BRAF mutation shown to promote PGE2 synthesis. This study was conducted to evaluate COX-2 expression in a large cohort of Middle Eastern Papillary Thyroid Carcinoma (PTC) and further evaluate the prognostic significance of COX-2 expression in strata of BRAF mutation status. BRAF mutation analysis was performed by Sanger sequencing and COX-2 expression was evaluated immunohistochemically using tissue microarray. COX-2 over-expression was noted in 43.2% (567/1314) of cases and was significantly associated with poor prognostic markers such as extra-thyroidal extension, lymph node metastasis and higher tumor stage. COX-2 was also an independent predictor of poor disease-free survival (DFS). Most notably, the association of COX-2 expression with DFS differed by BRAF mutation status. COX-2 over-expression was associated with poor DFS in BRAF mutant but not BRAF wild-type PTCs with the multivariate-adjusted hazard ratio of 2.10 (95% CI = 1.52 - 2.92; p < 0.0001) for COX-2 over-expressed tumors in BRAF mutant PTC. In conclusion, the current study shows that COX-2 plays a key role in prognosis of PTC patients. Furthermore, a significant association of COX-2 expression with poor DFS was noted in BRAF mutated tumors. Our data suggests the potential therapeutic role of COX-2 inhibition in patients with BRAF mutated PTC.

Citation Format: Rong Bu, Sandeep K. Parvathareddy, Abdul K. Siraj, Padmanaban Annaiyappanaidu, Kaleem Iqbal, Maha Al Rasheed, Wael Haqawi, Khawla S. Al-Kuraya. Prognostic significance of COX-2 over-expression in BRAF mutated Middle Eastern PTC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 729.

Recurrent Somatic MAP2K1 Mutations in Papillary Thyroid Cancer and Colorectal Cancer

Mitogen-activated protein kinase kinase 1 (MAP2K1) is a dual specificity protein kinase that phosphorylates both threonine and tyrosine residues in ERK. MAP2K1 mutations have been identified in several cancers. However, their role in Middle Eastern papillary thyroid cancer (PTC) and colorectal cancer (CRC) is lacking. In this study, we evaluated the prevalence of MAP2K1 mutations in a large cohort of Middle Eastern PTC and CRC using whole-exome and Sanger sequencing technology. In the discovery cohort of 100 PTC and 100 CRC cases (comprising 50 MAPK mutant and 50 MAPK wildtype cases each), we found one MAP2K1 mutation each in PTC and CRC, both of which were MAPK wildtype. We further analyzed 286 PTC and 289 CRC MAPK wildtype cases and found three MAP2K1 mutant PTC cases and two MAP2K1 mutant CRC cases. Thus, the overall prevalence of MAP2K1 mutation in MAPK wildtype cases was 1.1% (4/336) in PTC and 0.9% (3/339) in CRC. Histopathologically, three of the four MAP2K1 mutant PTC cases were follicular variant and all four tumors were unifocal with absence of extra-thyroidal extension. All the three CRC cases harboring MAP2K1 mutation were of older age (> 50 years) and had moderately differentiated stage II/III tumors located in the left colon. In conclusion, this is the first comprehensive report of MAP2K1 somatic mutations prevalence in PTC and CRC from this ethnicity. The mutually exclusive nature of MAP2K1 and MAPK mutations suggests that each of these mutation may function as an initiating mutation driving tumorigenesis through MAPK signaling pathway.

Abstract 3546: Prevalence of Lynch Syndrome among Middle Eastern endometrial cancer using targeted next generation sequencing

Endometrial carcinoma (EC) is the second most common gynecologic cancer worldwide. Although most ECs are sporadic, 2%-5% tend to be familial, with Lynch syndrome (LS) being the most commonly associated. The purpose of this study was to identify the incidence of LS in a large cohort of Middle eastern ECs and determine the feasibility of microsatellite instability (MSI) screening by immunohistochemistry (IHC) followed by molecular screening in deficient cases. We performed screening of 436 unselected EC for MSI status using IHC, followed by Target Capture sequencing of MSI deficient cases. MLH1 methylation analysis was performed by Real-time PCR, for cases showing deficient MLH1 by IHC. Complete loss of tumor nuclear protein expression in at least one of the four MMR genes was noted in 12.2% (53/436) of EC cases with 32 cases being MLH1 deficient, 10 MSH2 deficient, five MSH6 deficient and six PMS2 deficient. Of the 53 EC cases showing loss of expression in MMR genes, germline MMR mutations were found in four cases (0.9%). Promoter methylation analysis of 32 MLH1 deficient cases showed four cases to be unmethylated (12.5%). Our current study highlights the incidence of LS among patients with EC in Saudi Arabia. Screening of all EC patients using immunohistochemistry and reflex MLH1 promoter methylation testing followed by gene sequencing is feasible and desirable.

Citation Format: Sandeep K. Parvathareddy, Abdul K. Siraj, Rong Bu, Tariq Masoodi, Saud Azam, Wael Haqawi, Khadija Alobaisi, Maha Alrasheed, Valorie Balde, Nabil Siraj, Mark R. Diaz, Laila Ghazwani, Felisa DeVera, Hassan AlDossari, Khawla S. Al-Kuraya. Prevalence of Lynch Syndrome among Middle Eastern endometrial cancer using targeted next generation sequencing [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3546.