Elevated SOX11 expression distinguishes basal-like human breast cancer.

Patients diagnosed with basal-like breast cancer face a more aggressive disease course and more dismal prognosis than patients diagnosed with luminal A and luminal B breast cancer molecular subtypes (1-4). We mined published microarray data (5, 6) to understand in an unbiased fashion the most distinguishing transcriptional features of tumors from patients with basal or basal-like subtype breast cancer. We observed transcriptome-wide differential expression of SRY-box 11, SOX11, when comparing tumors of patients with basal-like breast cancer with that of other PAM50 molecular subtypes. SOX11 mRNA was present at significantly higher quantities in the tumors of patients with basal-like breast cancer. Analysis of patient survival data revealed that SOX11 primary tumor expression was correlated with overall survival, with higher SOX11 associated with inferior outcomes - in basal-like patients but not in luminal A, luminal B, HER2+, or normal-like patients. Elevated SOX11 expression appears to distinguish basal-like human breast cancer from the other molecular subtypes.

SOX11 is a sensitive and specific marker for pulmonary high-grade neuroendocrine tumors

Background Synaptophysin (SYN), chromogranin A (CGA), CD56 and insulinoma-associated protein 1 (INSM1) are proposed neuroendocrine (NE) markers used for diagnosis of pulmonary NE tumors. These NE markers have been identified in subsets of non-NE tumors requiring differential diagnosis, thus we sought to explore new NE markers. Methods We evaluated the immunohistochemical expression of SOX11, a transcription factor involved in neurogenesis, in pulmonary NE tumors and large cell carcinomas (LCCs). Results We found that SOX11 showed a sensitivity similar to INSM1 and CGA, and less than SYN and CD56 in small cell lung carcinomas (SCLCs) and large cell neuroendocrine carcinomas (LCNECs). While SOX11 is more specific than the other four markers for diagnosis of high-grade neuroendocrine carcinomas (HG-NECs) because 1) None of LCCs (0/63), the most challenging non-NE tumor type for differential diagnosis due to overlapped morphology with LCNECs displayed SOX11 positivity. While expression of at least one of SYN, CGA, CD56 or INSM1 was identified in approximately 60% (18/30) of LCCs. 2) SOX11 was only expressed in 1 of 37 carcinoid tumors in contrast to diffuse expression of SYN, CGA, CD56 and INSM1. In HG-NECs, we noticed that SOX11 was a good complementary marker for SCLC diagnosis as it was positive in 7 of 18 SYN−/CGA−/CD56− SCLCs and 3 of 8 SYN−/CGA−/CD56−/INSM1− SCLCs, and SOX11 positivity in 4 of 6 SYN−/CGA−/CD56− cases previously diagnosed as LCCs with NE morphology provides additional evidence of NE differentiation for reclassification into LCNECs, which was further confirmed by electromicroscopical identification of neurosecretory granules. We also found SOX11 expression cannot predict the prognosis in patients with HG-NECs. Conclusions Therefore, SOX11 is a useful complementary transcriptional NE marker for diagnosis and differential diagnosis of SCLC and LCNEC.

SOX11 Functions As an Oncogene in Lmo2-Driven T-Cell Lymphoblastic Leukemia (T-ALL)

Background: T-lineage acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy that accounts for 10%-15% of pediatric and 25% of adult ALL cases. Although the prognosis of T-ALL has been improving over time, the outcome of T- ALL patients with primary resistant or relapsed leukemia remains poor. Thus, further advances in the treatment of T-ALL require the identification of new targets for the development of highly specific molecularly targeted drugs. SRY-related HMG-box 11 (SOX11) is a member of the SOXC family, which also includes SOX4 and SOX12. SOX11 is single-exon gene that encodes a transcription factor, but its molecular properties and functions remain incompletely understood. Expression of SOX11 is strongly associated with neurogenic activity, and it is confined to the central nervous system. Aberrant SOX11 upregulation has been observed in several cancer types, such as medulloblastoma, glioma, and B- and T-cell lymphomas. Under physiological conditions, SOX11 is absent in the T-cell lineage. However, SOX11 expression is consistently found in a subset of TAL/LMO T-ALL cases characterized by an abundancy of PTEN mutations and an underrepresentation of NOTCH mutations. Since the expression of SOX11 is restricted to a malignant context, we postulate that SOX11 might act as an oncogene in T-ALL. Aims: We want to assess SOX11's potential to promote a (pre)leukemic state, and to identify the role of SOX11 during oncogenic transformation in vivo. Methods: We generated a R26-SOX11 knock-in mouse model that allows conditional SOX11 expression in thymocytes, by using Lck-Cre (SL). Using this model, we analyzed the (immuno)phenotype and transcriptome of T-cell populations in 8- to 12-weeks old mice. In the future, we will also perform a syngeneic transplantation of SL thymocytes into sublethally irradiated mice to assess their colonizing potential. Additionally, we have set up an aging cohort of SL mice to investigate whether expression of SOX11 suffices to induce malignant transformation. Since the expression of SOX11 is associated with the TAL/LMO subgroup, we also crossed SL mice with a well-established murine T-ALL model, CD2-Lmo2, to give rise to mice that express both transgenes in their thymocytes (SCL). An aging cohort of this T-ALL model was followed, and we generated a survival curve and collected biological samples. These tumor samples are being analyzed, and their transcriptomic profile will be compared with that of mice overexpressing Lmo2 only. Lastly, we will lentivirally transduce human T-ALL cell lines from the TAL/LMO subgroup using a vector for SOX11 expression. These cell-lines will be used to study the consequences of expressing this transcription factor in a pre-established malignant setting. Results: In order to determine the effects of SOX11 expression in T-cells, we collected and analyzed blood, spleen, and thymus of 12-weeks old SL mice and their Cre-negative littermates (WT). To validate this model, we performed real-time PCR and immunoblotting to confirm the overexpression of SOX11 in T-cells. Interestingly, we observed a significant reduction in the number of lymphocytes in the peripheral blood and in the spleen of SL mice. Furthermore, significant changes were found in the proportions of all thymic populations, featuring an increase in double negative (DN) T-cells (Fig. 1A), particularly the DN3 subpopulation (Fig. 1B), and a decreased double positive CD4/CD8 fraction (DP). Based on that finding, we decided to sort out DN3 and DP cells from WT and SL thymi, and performed RNA-sequencing to further characterize the effect of SOX11 in these cells. In addition, we are following a cohort of SL mice, but so far no tumor formation was observed (average age of the cohort=300-days old). On the other hand, simultaneous overexpression of SOX11 and Lmo2 greatly accelerated the development of T-cell malignancies in SCL mice when compared with CD2-Lmo2 mice (Fig. 1C; median survival of 177 days versus 307; p<0.0001), revealing a synergistic effect upon combination of both genetic events. Not surprisingly, most tumors were composed of immature T-cells, mainly DN cells, and no noteworthy differences were found between the composition and location of SCL and CD2-Lmo2 tumors. Conclusion: We showed that SOX11 skews the normal development of thymocytes in vivo. Additionally, we developed a murine SOX11 T-ALL model, thus confirming an oncogenic role for SOX11. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

SOX11, CD70 and Treg cells configure the tumor immune microenvironment of aggressive mantle cell lymphoma

Mantle cell lymphoma (MCL) is a mature B-cell neoplasm with a heterogeneous clinical and biological behavior. SOX11 oncogenic expression contributes to the aggressiveness of these tumors by different mechanisms including tumor and stromal cell interactions. However, the precise composition of the immune cell microenvironment of MCL, its possible relationship to SOX11 expression, and how it may contribute to tumor behavior is not well known. Here, we performed an integrative transcriptome analysis of 730 immune-related genes combined with the immune cell phenotype analysis by immunohistochemistry in SOX11+ and SOX11- primary nodal MCL cases and non-neoplastic reactive lymph nodes (RLN). SOX11+ MCL had a significant lower T-cell intratumoral infiltration compared to negative cases. A reduced expression of MHCI/II-like and T-cell costimulation and signaling activation related transcripts was significantly associated with poor clinical outcome. Moreover, we identified CD70 as a SOX11 direct target gene, whose overexpression was induced in SOX11+ but not SOX11- tumor cells by CD40L in vitro. CD70 was overexpressed in primary SOX11+ MCL and it was associated with an immune unbalance of the tumor microenvironment characterized by increased number of effector Treg cell infiltration, higher proliferation, and aggressive clinical course. CD27 was expressed with moderate to strong intensity in 76% of cases. Overall, our results suggest that SOX11 expression in MCL is associated with an immunosuppressive microenvironment characterized by CD70 overexpression in tumor cells, increased Treg cell infiltration and downmodulation of antigen-processing and -presentation and T-cell activation that could promote MCL progression and represent a potential target for tailored therapies.

Mantle Cell Lymphoma: An Immunomorphologic Study with SOX11 from a Tertiary Care Cancer Centre in Southern India

Introduction: Mantle Cell Lymphoma (MCL) is a relatively rare Non-Hodgkin Lymphoma (NHL) of mature B cells forming 5-7% of NHL. SOX11 has emerged as a useful antibody in the diagnosis of MCL with prognostic significance. Aim: To evaluate the immunomorphologic features and significance of SOX11 expression in MCL at a tertiary care cancer institute. Materials and Methods: This was a descriptive study which was conducted at a tertiary care cancer centre in Southern India over a period of five years from January 2013 to December 2017. Seventy six cases of newly diagnosed MCL with paraffin blocks were included in the study. Immunohistochemistry (IHC) with a panel of antibodies including SOX11 was carried out on Formalin Fixed Paraffin Embedded (FFPE) sections. Morphologic, immunologic findings were analysed and correlated with clinical data and survival, using Chi-square and Independent sample t-test to compare data and Kaplan-Meir method with Log Rank test for survival analysis. Results: Mantle Cell Lymphoma (MCL) formed in 5.8% of NHL with a striking male predominance (M:F ratio, 4.4:1), with mean age of 58 years at presentation and females at a younger age. Nearly 80% of patients presented at an advanced stage. Cervical lymphadenopathy was the most common presenting feature, followed by involvement of the gastrointestinal tract. There were 59 cases of classic and 17 cases of blastoid and pleomorphic MCL, with diffuse pattern being the most common in 36 (47.4%) cases. In the present study, 64 (92.8%) cases expressed SOX11 and showed heterogeneous staining with high expression in 34 (53.1%) cases and low expression in 30 (46.9%) cases. Ki-67 proliferation of more than 30% was seen in 52 (68.4%) cases and 30% or less in 24 (31.6%) cases. None of these findings had statistically significant correlation with survival, though high Ki-67, high MCL International Prognostic Index (MIPI) and blastoid/pleomorphic cases had relatively worse Overall Survival (OS). Conclusion: MCL is a disease of the elderly and in the present study it affected females at a slightly younger age as compared to males. SOX11 expression was heterogeneous in neoplastic cells and was complementary to cyclin D1 for diagnosis of MCL however, the staining intensity had no effect on survival.

Regulation of SOX11 expression through CCND1 and STAT3 in mantle cell lymphoma

The neural transcription factor SOX11 is usually highly expressed in typical mantle cell lymphoma (MCL), but it is absent in the more indolent form of MCL. Despite being an important diagnostic marker for this hard-to-treat malignancy, the mechanisms of aberrant SOX11 expression are largely unknown. Herein, we describe 2 modes of SOX11 regulation by the cell-cycle regulator cyclin D1 (CCND1) and the signal transducer and activator of transcription 3 (STAT3). We found that ectopic expression of CCND1 in multiple human MCL cell lines resulted in increased SOX11 transcription, which correlated with increased acetylated histones H3K9 and H3K14 (H3K9/14Ac). Increased H3K9/14Ac and SOX11 expression was also observed after histone deacetylase 1 (HDAC1) or HDAC2 was depleted by RNA interference or inhibited by the HDAC inhibitor vorinostat. Mechanistically, we showed that CCND1 interacted with and sequestered HDAC1 and HDAC2 from the SOX11 locus, leading to SOX11 upregulation. Interestingly, our data revealed a potential inverse relationship between phosphorylated Y705 STAT3 and SOX11 expression in MCL cell lines, primary tumors, and patient-derived xenografts. Functionally, inactivation of STAT3 by inhibiting the upstream Janus kinase (JAK) 1 or JAK2 or by STAT3 knockdown was found to increase SOX11 expression, whereas interleukin-21 (IL-21)–induced STAT3 activation or overexpression of the constitutively active form of STAT3 decreased SOX11 expression. In addition, targeting SOX11 directly by RNA interference or indirectly by IL-21 treatment induced toxicity in SOX11+ MCL cells. Collectively, we demonstrate the involvement of CCND1 and STAT3 in the regulation of SOX11 expression, providing new insights and therapeutic implications in MCL.

SOX11: friend or foe in tumor prevention and carcinogenesis?

Sex-determining region Y-related high-mobility-group box transcription factor 11 (SOX11) is an essential member of the SOX transcription factors and has been highlighted as an important regulator in embryogenesis. SOX11 studies have only recently shifted focus from its role in embryogenesis and development to its function in disease. In particular, the role of SOX11 in carcinogenesis has become of major interest in the field. SOX11 expression is elevated in a wide variety of tumors. In many cancers, dysfunctional expression of SOX11 has been correlated with increased cancer cell survival, inhibited cell differentiation, and tumor progression through the induction of metastasis and angiogenesis. Nevertheless, in a limited number of malignancies, SOX11 has also been identified to function as a tumor suppressor. Herein, we review the correlation between the expression of SOX11 and tumor behaviors. We also summarize the mechanisms underlying the regulation of SOX11 expression and activity in pathological conditions. In particular, we focus on the pathological processes of cancer targeted by SOX11 and discuss whether SOX11 is protective or detrimental during tumor progression. Moreover, SOX11 is highlighted as a clinical biomarker for the diagnosis and prognosis of various human cancer. The information reviewed here should assist in future experimental designs and emphasize the potential of SOX11 as a therapeutic target for cancer.