Daniel Steinbach

The scaffold protein family of IQ motif-containing GTPase-activating proteins (IQGAP1, 2, and 3) share a high degree of homology and comprise six functional domains. IQGAPs bind and regulate the cytoskeleton, interact with MAP kinases and calmodulin, and have GTPase-related activity, as well as a RasGAP domain. Thus, IQGAPs regulate multiple cellular processes and pathways, affecting cell division, growth, cell–cell interactions, migration, and invasion. In the past decade, significant evidence on the function of IQGAPs in signal transduction during carcinogenesis has emerged. Compared with IQGAP1, IQGAP2 and IQGAP3 were less analyzed. In this review, we summarize the different signaling pathways affected by IQGAP2 and IQGAP3, and the antithetic roles of IQGAP2 and IQGAP3 in different types of cancer. IQGAP2 expression is reduced and plays a tumor suppressor role in most solid cancer types, while IQGAP3 is overexpressed and acts as an oncogene. In lymphoma, for example, IQGAPs have partially opposite functions. There is considerable evidence that IQGAPs regulate a multitude of pathways to modulate cancer processes and chemoresistance, but some questions, such as how they trigger this signaling, through which domains, and why they play opposite roles on the same pathways, are still unanswered.

The progression of non-muscle-invasive bladder cancer (NMIBC) to muscle-invasive bladder cancer (MIBC) is a major challenge in urologic oncology. However, understanding of the molecular processes remains limited. The dysregulation of IQGAP2 is becoming increasingly evident in most tumor entities, and it plays a role in multiple oncogenic pathways, so we evaluated the role of IQGAP2 in bladder cancer. IQGAP2 was downregulated in tumors compared with normal urothelium tissues and cells. IQGAP2 effectively attenuated bladder cancer cell growth independently from apoptosis. Reduced IQGAP2 promoted EMT in bladder cancer cells via activation of the MAPK/ERK pathway. In addition, IQGAP2 might influence key cellular processes, such as proliferation and metastasis, through the regulation of cytokines. In conclusion, we suggest that IQGAP2 plays a tumor-suppressing role in bladder cancer, possibly via inhibiting the MAPK/ERK pathway and reducing cytokines.

Bladder cancer (BC) is characterised by a high recurrence and progression rate. However, the molecular mechanisms of BC progression remain poorly understood. BCL9L, a coactivator of β-catenin was mutated in the 5′ and 3′ untranslated regions (UTRs). We assessed the influence of UTRs mutations on BCL9L, and the role of BCL9L and Wnt/β-catenin signalling in BC cells. UTR mutations were analysed by a luciferase reporter. BCL9L protein was assessed by immunohistochemistry in BC tissues. Cell proliferation was examined by crystal violet staining and by the spheroid model. Moreover, migration and invasion were analysed in real-time using the xCelligence RTCA system. The A > T mutation at 3′ UTR of BCL9L reduces the luciferase reporter mRNA expression and activity. BCL9L is predominantly increased in dysplastic urothelial cells and muscle-invasive BC. Knockdown of BCL9L and inhibition of Wnt/β-catenin signalling significantly repress the proliferation, migration and invasion of Cal29 and T24. In addition, BCL9L knockdown reduces mRNA level of Wnt/β-catenin target genes in Cal29 but not in T24 cells. BCL9L and Wnt/β-catenin signalling play an oncogenic role in bladder cancer cells and seems to be associated with BC progression. Nevertheless, the involvement of BCL9L in Wnt/β-catenin signalling is cell-line specific.

Bladder cancer is a very heterogeneous disease and the molecular mechanisms of carcinogenesis and progression are insufficiently investigated. From the DNA sequencing analysis of matched non-muscle-invasive bladder cancer (NMIBC) and muscle-invasive bladder cancer (MIBC) samples from eight patients, we identified the tumour-associated gene SLC35F2 to be mutated in the 5′ and 3′ untranslated region (UTR). One mutation in 3′UTR increased the luciferase activity reporter, suggesting its influence on the protein expression of SLC35F2. The mRNA level of SLC35F2 was increased in MIBC compared with NMIBC. Furthermore, in immunohistochemical staining, we observed a strong intensity of SLC35F2 in single tumour cells and in the border cells of solid tumour areas with an atypical accumulation around the nucleus, especially in the MIBC. This suggests that SLC35F2 might be highly expressed in aggressive and invasive tumour cells. Moreover, knockdown of SLC35F2 repressed the growth of bladder cancer cells in the monolayer and spheroid model and suppressed migration and invasion of bladder cancer cells. In conclusion, we suggest that SLC35F2 is involved in bladder cancer progression and might provide a new therapeutic approach, for example, by the anti-cancer drug YM155, a cargo of the SLC35F2 transporter.

Routine second transurethral resection (TUR) for non-muscle-invasive bladder cancer (NMIBC) is common practice in Germany. Applicability of European Organization for Research and Treatment of Cancer (EORTC) and Spanish Urological Club for Oncological Treatment (CUETO) models in NMIBC patients is still controversial. Aim of the study was to assess the performance of EORTC and CUETO predictive models in NMIBC patients treated with second TUR.

Aim was to identify methylated genes with functional involvement in cisplatin‐resistance development of epithelial ovarian cancer (EOC). Genome‐wide analyses of hypermethylated CpG‐islands in resistant cell lines in combination with qRT‐PCR analyses were used to identify epigenetically silenced genes. EOC‐Type‐II tumors were analyzed for gene methylation and expression and TCGA data were interrogated in‐silico. Experiments revealed 37 commonly hypermethylated genes in resistant cells of which Tribbles 2 (TRIB2) showed the most pronounced downregulation on mRNA level and was characterized further. TRIB2 showed a reactivation after 5′‐Aza‐Cytidine treatment in resistant cells but a cisplatin‐dependent, prominent upregulation on mRNA level in sensitive cells, only. Re‐expression in resistant A2780 cells increased the sensitivity to cisplatin and other DNA‐damaging agents, but not taxanes. Contrary, knockdown of TRIB2 increased resistance to cisplatin in sensitive cells. TRIB2 was involved in the induction of a cisplatin‐dependent cell cycle arrest and apoptosis by influencing p21 and survivin expression. An increased Pt‐DNA‐adduct formation in TRIB2 re‐expressing cells did not translate in higher levels of dsDNA damage (yH2AX‐foci). Thus, TRIB2 is potentially involved in the signal transduction from nucleotide excision repair of intrastrand cross links. Importantly, patient stratification of two homogenous cohorts of EOC‐Type‐II patients from Jena (n = 38) and the TCGA (n = 149) by TRIB2 mRNA expression consistently revealed a significantly decreased PFS for patients with low TRIB2 levels (log‐rank p < 0.05). Tumors from resistant patients expressed the lowest levels of TRIB2. Downregulation of TRIB2 contributes to platin‐resistance and TRIB2 expression should be validated as prognostic and predictive marker for EOC.

Purpose Cytokeratin 20 (CK20) and insulin-like growth factor 2 (IGF2) were previously proposed to be elevated in clinical samples from patients with bladder cancer (BCa). A two cohort design validation study was used to assess the relevance for BCa detection by transcript quantitation of both markers in urine samples. Their diagnostic value was assessed in comparison with voided urine cytology (VUC). Methods RNA isolation was carried out using cellular sediments of urine samples from 196/103 histologically positive BCa patients, as well as 97/50 control subjects for the test (TC) and validation cohort (VC), respectively. Urinary transcript levels of CK20 and IGF2 were determined by qPCR. Results Relative transcript levels were significantly elevated 3.4/11-fold for CK20 and 188/64-fold for IGF2 (p < 0.001) in urine sediments of BCa patients compared to controls in the TC and VC, respectively. In a combined analysis, the resulting sensitivity (SN) (SN_TC: 77.9; SN_VC: 90.3%) and specificity (SP) (SP_TC: 88.0; SP_VC: 84.0%) were similar to that of VUC. The sensitivity of VUC in combination with CK20 and IGF2 was considerably increased (SN_TC: 94.6; SN_VC: 93.2%) while specificity was reduced (SP_TC: 72.0; SP_VC: 82.0%) compared to VUC alone in the test and validation cohort. Conclusions Transcript levels of IGF2 and CK20 enabled the detection of BCa with a diagnostic performance similar to VUC. Combined analysis of voided urine cytology together with altered transcript levels of CK20 and IGF2 enhanced sensitivity, but did not improve overall test performance.

Osteonecrosis (ON) is a debilitating side effect of anti-leukemic treatment. Thus far, the role of leukemic infiltration (LI) of bone is unclear. The first 30 children aged ≥10 years, who were enrolled in the ongoing OPAL trial and had MRI studies at diagnosis and at 6 months, were analyzed. MRI revealed extensive LIs in 24 (80%) patients. The signal abnormalities changed back to a physiological signal in 29 out of 30 children at 6 months. Of the 24 children with LIs at diagnosis, 3 (12.5%) developed ON ≥ II, whereas 4 (66.7%) patients without LIs subsequently developed ON ≥ II (p = .016). No differences between children initially presenting with/without LIs were observed concerning age, pubertal stage, white blood count, immunophenotype, and clinical presentation. Initial radiological LI of bone and, thus, single MRI at diagnosis cannot identify children at high risk of developing radiological ON at 6 months into treatment.