CD137 (4-1BB, TNFRSF9) plays a crucial role in T-cell activation, proliferation, and antiviral immunity. Biallelic TNFRSF9 variants cause CD137 deficiency, a rare inborn error of immunity characterized by Epstein-Barr virus (EBV)-induced hemophagocytic lymphohistiocytosis (HLH) and lymphoproliferation/malignancy. In this study, we aimed to characterize the clinical, immunological, and genetic spectrum of CD137 deficiency to provide insights into patient management. We recruited two patients carrying the same homozygous large deletion encompassing exons 1-6 of the TNFRSF9 gene and reviewed previously reported cases. The genetic defect was identified by whole-exome sequencing and confirmed by multiplex ligation-dependent probe amplification. Reported variants included missense, splice-site, and frameshift variants, large deletions, and compound heterozygous variants. A total of 14 patients, including the two newly reported cases, exhibited recurrent sinopulmonary infections and EBV viremia. HLH occurred in four patients (28.5%), including both newly reported patients, while lymphoma developed in seven patients (50%). Most patients were of Middle Eastern origin, and parental consanguinity was documented in 12 of 14 patients (85%). Hematopoietic stem cell transplantation (HSCT) was performed in 35.7% (5/14) of patients, with a median age of 9 years (range, 7-17 years) among four reported cases. All transplanted patients were alive at the last follow-up, whereas mortality occurred exclusively among non-transplanted patients, including EBV-positive cases. These findings expand the phenotypic and mutational spectrum of CD137 deficiency and highlight the importance of incorporating copy number variant analysis into exome-based diagnostic pipelines when conventional single-nucleotide variant analysis is inconclusive. HSCT remains the only potentially curative treatment, and early molecular diagnosis is essential to enable timely consideration of HSCT and to mitigate life-threatening EBV-driven immunopathology.

Lymphoproliferative disorders (LPDs) associated with inborn errors of immunity (IEI) are rare entities and their genetic basis is not well defined. We performed targeted deep sequencing using a panel of 529 genes to investigate the single nucleotide variants (SNVs), insertion/deletions (INDELs), structural rearrangements (SVs), and copy number variants (CNVs) in 16 lymphoproliferations associated with IEI belonging to a cohort of 14 patients. Histomorphologically, the cases were classified into B-cell hyperplasia (n = 1); polymorphic B-lymphoproliferative disorder (n = 8); polymorphic B-lymphoproliferative disorder with focal increased large cell component bordering large B cell lymphoma (n = 3); and large B-cell lymphoma (n = 4). Fourteen of the 16 cases were EBV positive. Across the patients, 40 variants were identified. The majority of the genes affected were those involved in DNA damage response pathways and transcriptional regulation. Pathogenic SNVs, INDELs, and CNVs were increased in cases with a large B cell component vs other cases. Heterozygous SNVs in protein interaction domains of EMSY were identified in 3 cases, suggesting that it may have a predisposing role in the development of lymphoproliferations. Deletions involving the TNFAIP3 gene (copy number losses) were also recurrent, identified in 3 of 16 cases (18.8

Accurate prediction of CNS relapse in DLBCL remains challenging despite existing models like IPI and CNS-IPI. This study aimed to develop a machine learning (ML)-based prognostic model. A retrospective cohort of 664 R-CHOP-treated DLBCL patients was analyzed; 44 (6.6%) experienced CNS relapse at a median of 9.3 months. ML models, including Random Survival Forests (RSF) and Gradient Boosting Machines (GBM), were developed and validated using the entire cohort (n = 664), irrespective of CNS relapse. RSF demonstrated high discriminative ability (C-index: 0.91) and low prediction error (Integrated Brier Score [IBS]: 0.057), while GBM yielded comparable performance (C-index: 0.88, IBS: 0.042), both outperforming traditional scores such as IPI and CNS-IPI. Key predictors included extranodal site number, high-risk organ involvement, and ECOG performance status, although ECOG lost significance in Fine and Gray competing risks analysis, likely due to early mortality. ML-based models offer enhanced predictive accuracy and support personalized CNS risk assessment in DLBCL.

Primary central nervous system large B-cell lymphoma (PCNS-LBCL) is a rare, aggressive lymphoma that affects immune-privileged sites. Immune checkpoint molecules have been implicated in its aggressive biology, and promising results have emerged from immune checkpoint inhibitor therapy in relapsed/refractory cases. This study evaluates the tumor microenvironment (TME), immune checkpoint molecule expression, and the relationship with 9p24.1 gene region alterations in a large cohort of PCNS-LBCL, with detailed quantitative analyses. Tissue microarrays were constructed with 57 PCNS-LBCL cases and 45 systemic non-germinal center diffuse large B-cell lymphoma (DLBCL) controls. Immunostaining for CD3, CD8, CD68, CD163, PD-1, PD-L1, PD-L2, EBER in situ hybridization (ISH), and FISH for PD-L1/PD-L2 copy number alterations and translocations were performed. Digital image analysis was used for quantitative evaluations, which were compared with clinical and pathologic parameters. PCNS-LBCL showed significantly lower T-cell and histiocyte presence in the TME compared with nodal DLBCL ( P <0.001), independent of preoperative steroid therapy. Cytotoxic T-cell ratio was higher in PCNS-LBCL ( P <0.001). PD-1, PD-L1, and PD-L2 expressions in the TME of PCNS-LBCL were 89%, 96%, and 90%, respectively, and were positively correlated with TME density. Tumor cell expressions of PD-L1 and PD-L2 were 31% and 34%, respectively. FISH alterations in the 9p24.1 region were infrequent and did not consistently correlate with protein expression in either PCNS-LBCL or DLBCL. Higher CD8+ T-cell and CD68+ histiocyte counts were associated with better survival in PCNS-LBCL. Lower TME density and high expression of PD-1/PD-L1/PD-L2 in PCNS-LBCL reflect the unique CNS microanatomy and may contribute to poorer prognosis. These findings support the potential benefit of immune checkpoint inhibitors in treating PCNS-LBCL, aligning with ongoing clinical trials and current literature.

Biological differences exist between invasive ductal carcinoma (IDC) and IDC + ductal carcinoma in situ (DCIS) tumors including variations in tumor grade, hormone receptor status, human epidermal growth factor receptor 2 (HER2) expression, proliferative activity and molecular subtype. The present study evaluated the impact of the coexistence of IDC + DCIS on tumor microenvironment, tumor-infiltrating lymphocytes (TILs), clinical and pathological features, prognosis and survival. A total of 165 patients with IDC and 404 with IDC + DCIS were enrolled and treated in the outpatient clinic, Hacettepe University Department of Medical Oncology (Ankara, Turkey) between January 2014 and July 2021. Compared with IDC, patients with IDC + DCIS were more likely to be hormone receptor-positive and had a lower rate of mastectomy and Ki-67 index (both P<0.05). The co-existence of DCIS was associated with significantly improved overall survival (OS) and disease-free survival (DFS) (both P<0.05). Furthermore, patients with IDC had 2.14-fold higher odds of death and 2.44-fold higher odds of recurrence/distant metastasis/death than patients with IDC + DCIS. The present study supports the behavioral differences of IDC and IDC + DCIS and suggests these two groups of tumors may also behave differently in terms of antitumor immune response. As the DCIS component is positively associated with favorable prognostic features, the presence of the DCIS is associated with improved DFS and OS. DCIS accompaniment may have prognostic value for patients with breast cancer.

Background. Non-Hodgkin lymphoma of the larynx in children is a rare condition. Diagnosis is difficult as its symptoms are usually attributed to respiratory tract infections and pubertal voice changes. Case Presentations. We report two children diagnosed with laryngeal B-cell lymphoma based on imaging and histopathological findings. We also review other pediatric cases of laryngeal lymphoma documented in the literature, detailing tumor locations, lymphoma types, stages, etiological factors, and treatment regimens of these patients. Conclusion. Diagnosis of laryngeal lymphoma is challenging. Although certain imaging features can be suggestive of the disease, a definitive diagnosis requires histopathological examination. Surgery is not required for the treatment, and chemotherapy is the main treatment approach. Early diagnosis is important.

Phosphodiesterase 4D (PDE4D) is a member of the phosphodiesterase family of enzymes, catalyzing the hydrolysis of cAMP second messenger and inhibiting cAMP signaling. Targeting PDE4D raises the intracellular cAMP levels, leading to apoptosis and cell cycle arrest in different tumor types. However, its contribution to drug resistance and metastasis is still elusive. lncRNAs are more than 200 nucleotides in length and carry out diverse functions including transcriptional regulation, and regulation of proteins or RNA molecules by direct binding and stabilization. LINC00152 is an oncogenic lncRNA that promotes survival, proliferation, epithelial-mesenchymal transition (EMT) and invasiveness in cancer cells. Despite being a driver in several key oncogenic processes, whether LINC00152 is an upstream regulator of PDE4D to drive endocrine resistance and metastasis in ER+ breast cancer remains to be elucidated. Here we showed that LINC00152 stabilizes PDE4D mRNA, thus driving tamoxifen resistance upon deactivation of the cAMP/PKA/CREB axis. Overexpressing PDE4D rescues LINC00152-mediated tamoxifen resistance by blocking tamoxifen-induced ferroptosis. In addition, we demonstrated that inhibiting LINC00152 or PDE4D reduces the migration of endocrine resistant cells upon PKA-mediated blockage of TGF-β signaling. Targeting PDE4D using the clinically-tested PDE4D selective inhibitor, BPN14770 significantly reduces spontaneous metastasis in the highly aggressive, endocrine resistant-mimicking MMTV-PyMT model in vivo. Importantly, we showed that high levels of PDE4D mRNA is associated with worse metastasis-free survival in endocrine-treated ER+ breast cancer patients. Overall, we identified the highly oncogenic lncRNA, LINC00152 as an upstream regulator of PDE4D, which drives endocrine resistance and metastasis in the highly aggressive ER+ breast cancer. Ozge Saatci, Rashedul Alam, Kim-Tuyen Huynh-Dam, Aynur Isik, Meral Uner, Nevin Belder, Pelin Ersan, Unal M. Tokat, Burge Ulukan, Metin Cetin, Kubra Calisir, Mustafa E. Gedik, Hilal Bal, Ozlem Sener Sahin, Yasser Riazalhosseini, Denis Thieffry, Daniel Gautheret, Besim Ogretmen, Sercan Aksoy, Aysegul Uner, Aytekin Akyol, Ozgur Sahin. LINC00152-regulated PDE4D mediates drug resistance and metastasis in highly aggressive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr LB019.

Extramedullary involvement of acute myeloid leukemia (AML), aka myeloid sarcoma, is a rare phenomenon in acute megakaryoblastic leukemia with RBM15:: MRTFA(MKL1) fusion, which might mimic non-hematologic malignancies. A 7-month-old infant presented with leukocytosis, hepatosplenomegaly, multiple lymphadenopathies, and a solid mass in the right thigh. Initially, the patient was diagnosed with a malignant vascular tumor regarding the expression of vascular markers from the biopsy of the right thigh lesion that was performed after the inconclusive bone marrow biopsy. The second bone marrow biopsy, which was performed due to the partial response to sarcoma treatment, showed hypercellular bone marrow with CD34 and CD61-positive spindle cell infiltration and > 20% basophilic blasts with cytoplasmic blebs. RNA sequencing of soft tissue biopsy revealed the presence of RBM15::MRTFA(MKL1) fusion. Based on these findings, myeloid sarcoma/AML with RBM15::MRTFA(MKL1) fusion diagnosis was made. AML with RBM15::MRTFA(MKL1) fusion can initially present as extramedullary lesions and might cause misdiagnosis of non-hematologic malignancies.

Abstract Endocrine therapies, modulating ER level and/or activity, and the CDK4/6 inhibitors are among the standard-of-care (SOC) therapies used in estrogen receptor-positive (ER+) breast cancer. However, most ER+ breast cancer patients eventually develop resistance to SOC, representing a major clinical challenge that reduces clinical outcome. Therefore, elucidating the common mechanisms of sensitivity and resistance to SOC therapies, and identifying novel actionable targets are urgently needed. Here, we demonstrated that cell death induced by endocrine therapies and CDK4/6 inhibitors involves toxic PARP1 trapping and generation of a functional BRCAness (i.e., BRCA1/2 deficiency) phenotype, leading to transcriptional blockage. We showed that this is achieved by activation of the cAMP/reactive oxygen species (ROS)/DNA damage axis upon downregulation of phosphodiesterase 4D (PDE4D). Importantly, we identified PDE4D as a novel ER target gene that in turn stimulates ER activity in a feedforward loop in endocrine-responsive models. However, during SOC resistance, an ER-to-EGFR switch induces PDE4D overexpression via c-Jun. Inhibition of PDE4D using BPN14770, the first-in-class PDE4D allosteric inhibitor that has successfully completed Phase II trials in Fragile X syndrome, reinstates PARP1 trapping and BRCAness, leading to drug sensitization in vitro and in vivo. Furthermore, inhibition of EGFR or PARP1 recapitulates the effects of PDE4D targeting and overcomes SOC resistance irrespective of the BRCA1/2 status in cell line models, primary cultures and organoids of endocrine resistant ER+ PDXs. Notably, we demonstrated that high PDE4D mRNA and protein expression is associated with dramatically worse disease-free survival and overall survival in endocrine therapy-treated ER+ breast cancer. Given the availability of potent and non-toxic PDE4D inhibitors, and clinically approved EGFR and PARP1 inhibitors, our findings have great translational potential to improve the clinical outcome of refractory ER+ breast cancers. Citation Format: Ozge Saatci, Metin Cetin, Meral Uner, Unal M. Tokat, Ioulia Chatzistamou, Elodie Montaudon, Aytekin Akyol, Sercan Aksoy, Aysegul Uner, Elisabetta Marangoni, Mathew Sajish, Ozgur Sahin. Targeting PDE4D reinstates toxic PARP trapping via cAMP-ROS-DNA damage axis and restores the efficacy of standard of care in treatment-refractory ER+ breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 563.

Chronic granulomatous disease (CGD) is a congenital disorder impairing phagocyte function, causing recurrent, life-threatening infections, and is rarely seen in adulthood. We present a 36-year-old male initially diagnosed with pneumonia. Bronchoalveolar lavage and blood cultures yielded Burkholderia multivorans/cepacia complex, sputum cultures Aspergillus niger. Despite the antimicrobial treatment, his condition deteriorated. His clinical and laboratory findings indicated hemophagocytic lymphohistiocytosis. He responded to steroids. Nitroblue tetrazolium and dihydroergotamine-123 tests confirmed CGD. Whole exome sequencing identified NCF1 deletion. He received interferon-gamma, voriconazole, and trimethoprim-sulfamethoxazole. Allogeneic hematopoietic stem cell transplantation was planned. This case report improves understanding of CGD in adults, aiming to enhance diagnostic and therapeutic strategies.

Background: Multicentric Castleman disease (MCD) is a rare, aggressive lymphoproliferative disorder. Human herpesvirus-8 (HHV-8) has an important role in the pathogenesis of the disease and its association with Kaposi’s sarcoma has been reported, especially in people living with human immunodeficiency virus (HIV). In this report, we present the case of HHV-8 positive MCD accompanied by Kaposi’s sarcoma and multiple myeloma in an HIV-negative patient. Case Report: A 78-year-old man with Kaposi’s sarcoma presented with B symptoms, pancytopenia, lymphadenopathy, and splenomegaly. The bone marrow biopsy demonstrated 70% lambda-restricted monotypic plasma cell infiltration consistent with plasma dyscrasia. Also, the patient was diagnosed with HHV-8 positive MCD as a result of inguinal lymph node excisional biopsy. Treatment was initiated including ganciclovir and methylprednisolone and followed by rituximab. The patient passed away at the 24th hour of rituximab infusion due to shock. Conclusions: MCD and associated malignancies are difficult to treat and have a poor prognosis. More studies and data are needed to manage these patients.

Abstract Trastuzumab emtansine (T-DM1) was the first and one of the most successful antibody–drug conjugates (ADC) approved for treating refractory HER2-positive breast cancer. Despite its initial clinical efficacy, resistance is unfortunately common, necessitating approaches to improve response. Here, we found that in sensitive cells, T-DM1 induced spindle assembly checkpoint (SAC)-dependent immunogenic cell death (ICD), an immune-priming form of cell death. The payload of T-DM1 mediated ICD by inducing eIF2α phosphorylation, surface exposure of calreticulin, ATP and HMGB1 release, and secretion of ICD-related cytokines, all of which were lost in resistance. Accordingly, ICD-related gene signatures in pretreatment samples correlated with clinical response to T-DM1–containing therapy, and increased infiltration of antitumor CD8+ T cells in posttreatment samples was correlated with better T-DM1 response. Transforming acidic coiled-coil containing 3 (TACC3) was overexpressed in T-DM1–resistant cells, and T-DM1 responsive patients had reduced TACC3 protein expression whereas nonresponders exhibited increased TACC3 expression during T-DM1 treatment. Notably, genetic or pharmacologic inhibition of TACC3 restored T-DM1–induced SAC activation and induction of ICD markers in vitro. Finally, TACC3 inhibition in vivo elicited ICD in a vaccination assay and potentiated the antitumor efficacy of T-DM1 by inducing dendritic cell maturation and enhancing intratumoral infiltration of cytotoxic T cells. Together, these results illustrate that ICD is a key mechanism of action of T-DM1 that is lost in resistance and that targeting TACC3 can restore T-DM1–mediated ICD and overcome resistance. Significance: Loss of induction of immunogenic cell death in response to T-DM1 leads to resistance that can be overcome by targeting TACC3, providing an attractive strategy to improve the efficacy of T-DM1.

Abstract Introduction Primary hyperparathyroidism (PHP) and malignancies are the most common causes of hypercalcemia. Nevertheless, PHP might be observed in coexisting with malignancies. We aimed to present a patient who underwent surgery for PHP and was diagnosed with thyroid MALToma. Clinical Case A 65-year-old female presented with fatigue for one year. The patient's medical history was unremarkable. On examination, thyroid gland was non-palpable. On laboratory, serum calcium (Ca), phosphorus (P) and parathormone (PTH) levels were 11 mg/dL (R: 8.8-10.6), 2.4 mg/dL (R: 2.5-4.5) and 157 pg/mL, respectively; vitamin-D was 23.63 µg/L and increased urinary Ca (400 mg per-day). She was euthyroid, and thyroid antibody elevated. Ultrasound (US) revealed multiple hypoechoic areas and a lesion (18×14 mm) in the vicinity of inferior right thyroid gland. Parathyroid scintigraphy revealed significant increase of metabolic activity posterior to the right lobe of the thyroid. She underwent right thyroid lobectomy thyroidectomy. Pathology revealed mucosa-associated lymphoid tissue (MALT) lymphoma of the thyroid. No parathyroid lesion noted. Then she was referred to our clinic. US revealed hypoechoic areas at remaining thyroid with no extra finding. We performed tru-cut biopsy from thyroid lesion. On immunochemistry, lymphoid cells were diffusely immunoreactive for CD3, CD5, CD20 and CD43 in the ymphocytes. Ki-67 index was 40%. Hence, the diagnosis of MALT lymphoma of the thyroid gland in the background of Hashimoto's thyroiditis. PTH staining of patient's previous pathology specimen was unremarkable. Pretreatment baseline 18F-flurodeoxyglucose PET/CT (FDG) revealed increased uptake (SUVmax: 5.1) in hypodense nodular structure in the posterior left lobe of the thyroid gland (Figure 1). FDG was suggestive of stage IE. Mild 18F-FCH uptake was observed suspected as parathyroid lesion next to the inferior left lobe. 4D-CT showed similar results. All imaging methods and we examined patient via US that revealed hypoechoic lesion with polar blood supply in the left lobe inferior (parathyroid adenoma). The patient were under rituximab 375 mg/m2 per week for 4 cycles. At the end of treatment, there were no sign of residual disease. Reoperation has not been planned due to the improvement of the patient's symptoms, and lymphoma with indolent course. Conclusion 10% of PHP cases may have a concomitant malignancy, while association with lymphoma is even rarer. MALT lymphoma of the thyroid gland is a rare malignancy with an indolent course. The combination of these two rare conditions hard to orchestrate. As in our case, detection of parathyroid lesions becomes more difficult in the background of a low grade lymphoma. Indolent lymphomas have limited sensitivity with FDG. FCH could be more sensitive for discriminating parathyroid lesions and indolent lymphomas. It may be useful to confirm the localization of the PHP in such cases using multiple techniques involving FCH.Figure 1.Pre-treatment avid FCH uptake (A, B) and mild FDG uptake (C, D) related with thyroid MALToma; post-treatment complete remission shown in FDG (E, F); highly vascular paratracheal lesion at 4D-CT (G, H asterixis), the same lesion with mild FCH uptake (I-N arrows) and the same lesion with hypoechoic sonographic appearance evaluated as parathyroid adenoma (O arrow).