KIT expression in normal and neoplastic renal tissues: Immunohistochemical and molecular genetic analysis

Anti-CD117 immunotherapy to eliminate hematopoietic and leukemia stem cells

Precise replacement of diseased or dysfunctional organs is the goal of regenerative medicine and has appeared to be a distant goal for a long time. In the field of hematopoietic stem cell transplantation, this goal is now becoming tangible as gene-editing technologies and novel conditioning agents are entering the clinical arena. Targeted immunologic depletion of hematopoietic stem cells (HSCs), which are at the very root of the hematopoietic system, will enable more selective and potentially more effective hematopoietic stem cell transplantation in patients with hematological diseases. In contrast to current conditioning regimes based on ionizing radiation and chemotherapy, immunologic conditioning will spare mature hematopoietic cells and cause substantially less inflammation and unspecific collateral damage to other organs. Biological agents that target the stem cell antigen CD117 are the frontrunners for this purpose and have exhibited preclinical activity in depletion of healthy HSCs. The value of anti-CD117 antibodies as conditioning agents is currently being evaluated in early clinical trials. Whereas mild, antibody-based immunologic conditioning concepts might be appropriate for benign hematological disorders in which incomplete replacement of diseased cells is sufficient, higher efficacy will be required for treatment and elimination of hematologic stem cell malignancies such as acute myeloid leukemia and myelodysplastic syndrome. Antibody-drug conjugates, bispecific T-cell engaging and activating antibodies (TEAs), or chimeric antigen receptor (CAR) T cells might offer increased efficacy compared with naked antibodies and yet higher tolerability and safety compared with current genotoxic conditioning approaches. Here, we summarize the current state regarding immunologic conditioning concepts for the treatment of HSC disorders and outline potential future developments.

Histopathologic and Immunohistochemistry Findings in Feline Renal Cell Carcinoma

The biological behavior and immunohistochemical features of feline renal cell carcinoma (RCC) have not been well characterized. In the present study, immunohistochemical examinations were performed in 12 feline cases of RCC. The RCC consisted of solid ( n = 2), solid-tubular ( n = 2), tubular ( n = 3), papillary ( n = 2), tubulopapillary ( n = 2), and sarcomatoid ( n = 1) type lesions. Of the cases with RCC, 1 developed metastatic disease and 6 cases had no evidence of recurrence at 80 to 2292 days after surgery. One papillary-type tumor had cuboidal cells with scant cytoplasm and monomorphic nuclei, and the other had pseudostratified columnar cells with abundant cytoplasm. Immunohistochemistry revealed that the tumor cells in most cases were positive for cytokeratin (CK)7, CK20, KIT, and CD10, with the exception of cases of the solid type with clear cytoplasm (solid anaplastic), papillary type with columnar cells, and sarcomatoid types. A small number of tumor cells in the solid anaplastic and in the sarcomatoid types were positive for aquaporin-1. Increased expression of N-cadherin and Twist along with nuclear accumulation of β-catenin were observed in the sarcomatoid type. These results indicated that CK, KIT, and CD10 are relatively strongly expressed in most feline RCC. The solid anaplastic RCC exhibited CD10 expression with the absence of distal tubule marker expression. Although immunohistochemistry profiles were relatively consistent with those described in human RCC, the histopathologic features were different from those seen in humans. Epithelial-mesenchymal transition (EMT) marker expression in the current cases may suggest the involvement of an EMT-like mechanism in the development of sarcomatoid RCC in cats.

Identification and Validation of Radiographic Enhancement for Reliable Differentiation of CD117(+) Benign Renal Oncocytoma and Chromophobe Renal Cell Carcinoma

Purpose: The diagnostic differential for CD117/KIT(+) oncocytic renal tumor biopsies is limited to benign renal oncocytoma versus chromophobe renal cell carcinoma (ChRCC); however, further differentiation is often challenging and requires surgical resection. We investigated clinical variables that might improve preoperative differentiation of CD117(+) renal oncocytoma versus ChRCC to avoid the need for benign tumor resection.Experimental Design: A total of 124 nephrectomy patients from a single institute with 133 renal oncocytoma or ChRCC tumors were studied. Patients from 2003 to 2012 comprised a retrospective cohort to identify clinical/radiographic variables associated with renal oncocytoma versus ChRCC. Prospective validation was performed among consecutive renal oncocytoma/ChRCC tumors resected from 2013 to 2017.Results: Tumor size and younger age were associated with ChRCC, and multifocality with renal oncocytoma; however, the most reliable variable for ChRCC versus renal oncocytoma differentiation was the tumor:cortex peak early-phase enhancement ratio (PEER) using multiphase CT. Among 54 PEER-evaluable tumors in the retrospective cohort [19 CD117(+), 13 CD117(-), 22 CD117-untested], PEER classified each correctly as renal oncocytoma (PEER >0.50) or ChRCC (PEER ≤0.50), except for four misclassified CD117(-) ChRCC variants. Prospective study of PEER confirmed 100% accuracy of renal oncocytoma/ChRCC classification among 22/22 additional CD117(+) tumors. Prospective interobserver reproducibility was excellent for PEER scoring (intraclass correlation coefficient, ICC = 0.97) and perfect for renal oncocytoma/ChRCC assignment (ICC = 1.0).Conclusions: In the largest clinical comparison of renal oncocytoma versus ChRCC to our knowledge, we identified and prospectively validated a reproducible radiographic measure that differentiates CD117(+) renal oncocytoma from ChRCC with potentially 100% accuracy. PEER may allow reliable biopsy-based diagnosis of CD117(+) renal oncocytoma, avoiding the need for diagnostic nephrectomy. Clin Cancer Res; 24(16); 3898-907. ©2018 AACR.

Next-Generation Sequencing to Detect Deletion of RB1 and ERBB4 Genes in Chromophobe Renal Cell Carcinoma: A Potential Role in Distinguishing Chromophobe Renal Cell Carcinoma from Renal Oncocytoma

Overlapping morphologic, immunohistochemical, and ultrastructural features make it difficult to diagnose chromophobe renal cell carcinoma (ChRCC) and renal oncocytoma (RO). Because ChRCC is a malignant tumor, whereas RO is a tumor with benign behavior, it is important to distinguish these two entities. We aimed to identify genetic markers that distinguish ChRCC from RO by using next-generation sequencing (NGS). NGS for hotspot mutations or gene copy number changes was performed on 12 renal neoplasms, including seven ChRCC and five RO cases. Matched normal tissues from the same patients were used to exclude germline variants. Rare hotspot mutations were found in cancer-critical genes (TP53 and PIK3CA) in ChRCC but not RO. The NGS gene copy number analysis revealed multiple abnormalities. The two most common deletions were tumor-suppressor genes RB1 and ERBB4 in ChRCC but not RO. Fluorescence in situ hybridization was performed on 65 cases (ChRCC, n = 33; RO, n = 32) to verify hemizygous deletion of RB1 (17/33, 52%) or ERBB4 (11/33, 33%) in ChRCC, but not in RO (0/32, 0%). In total, ChRCCs (23/33, 70%) carry either a hemizygous deletion of RB1 or ERBB4. The combined use of RB1 and ERBB4 fluorescence in situ hybridization to detect deletion of these genes may offer a highly sensitive and specific assay to distinguish ChRCC from RO.

Nephrogenic adenoma of the urinary tract: clinical, histological, and immunohistochemical characteristics

Nephrogenic adenoma is a benign condition of the urinary tract resulting from the displacement and seeding of renal tubular cells from the renal pelvis to the urethra. A retrospective series of 134 cases collected from four hospitals in three different countries was analyzed in this study. Recorded clinical data included age and sex, topography, urological antecedents, coexistent lesions, and follow-up. Cytonuclear and architectural features were reviewed, and PAX-8, p63, PSMA, S100A1, CEA, EMA, CD117, cannabinoid receptor CB1, AMACR, E-cadherin, and CD10 antibodies were included in an immunohistochemical panel. Males predominated (105 M/29 F) with an average age of 66 years (range, 14-96). Urothelial carcinoma was the most frequent clinical antecedent (43.2 %) and also the most common coexisting lesion (14 %). Tubular architecture was the most frequent pattern detected (40 %) although most cases showed a mixed pattern (45.5 %). Deep infiltrative growth into the muscularis propria occurred in two cases. EMA and PAX-8 were expressed in 100 % of nephrogenic adenomas, while E-cadherin reactivity was observed in 66.6 % of cases, cannabinoid receptor CB1 in 25 %, CD10 in 13.6 %, CD117 in 4.1 %, and AMACR in 2.7 %. For the rest of the antigens, no reactivity was found. The average time lapse between the pathological antecedent and the discovery of a nephrogenic adenoma was 32 months. We conclude that nephrogenic adenoma displays a broad spectrum of histological features that may mimic malignancy. In our experience, CB1 immunostaining adds a further argument in favor of a renal origin of this lesion. The combination of PAX-8+, p63-, and EMA + distinguishes nephrogenic adenoma from urothelial and prostate carcinoma, its most frequent malignant look-alikes.

Stem cell factor expression after renal ischemia promotes tubular epithelial survival

Background

Renal ischemia leads to apoptosis of tubular epithelial cells and results in decreased renal function. Tissue repair involves re-epithelialization of the tubular basement membrane. Survival of the tubular epithelium following ischemia is therefore important in the successful regeneration of renal tissue. The cytokine stem cell factor (SCF) has been shown to protect the tubular epithelium against apoptosis.

Methodology/Principal Findings

In a mouse model for renal ischemia/reperfusion injury, we studied how expression of c-KIT on tubular epithelium and its ligand SCF protect cells against apoptosis. Administration of SCF specific antisense oligonucleotides significantly decreased specific staining of SCF following ischemia. Reduced SCF expression resulted in impaired renal function, increased tubular damage and increased tubular epithelial apoptosis, independent of inflammation. In an in vitro hypoxia model, stimulation of tubular epithelial cells with SCF activated survival signaling and decreased apoptosis.

Conclusions/Significance

Our data indicate an important role for c-KIT and SCF in mediating tubular epithelial cell survival via an autocrine pathway.

KIT, PDGFRalpha and EGFR analysis in nephroblastoma

Nephroblastoma prognosis has dramatically improved, but an unfavourable prognostic subgroup warrants development of novel therapeutic strategies. Selective KIT, PDGFRalpha and epidermal growth factor receptor (EGFR) tyrosine kinase inhibition evolved as powerful targeted therapy for gastrointestinal stromal tumours and non-small-cell lung cancer. To investigate a potential role for tyrosine kinase inhibition, we analyzed 209 nephroblastomas for immunohistochemical KIT and EGFR expression, 63 nephroblastomas for mutations in KIT exons 9, 11, 13, EGFR exons 18, 19, 20 and 21, and all 209 nephroblastomas for PDGFRalpha exons 12, 14 and 18. Twenty-two tumours (10.5%) expressed KIT, 31 (14.8%) EGFR, and 10 (4.8%) both KIT and EGFR, respectively. KIT expression was relatively more common among high-risk tumours (6/27; 22.3%) compared to low-/intermediate-risk tumours (26/181; 14.4%). Nine patients deceased, four of which had high-risk tumours with KIT expression in two of four and EGFR expression in one of four. There were no KIT, PDGFRalpha or EGFR mutations. Our results suggest no significant contribution of KIT, EGFR or PDGFRalpha mutations to nephroblastoma pathogenesis. Despite a trend towards association of immunohistochemical KIT and EGFR expression with poor outcome in high-risk nephroblastomas, statistical analysis did not yield significant correlations in this subgroup. Therefore, it remains open if KIT, PDGFRalpha or EGFR tyrosine kinase inhibition constitute a therapeutic target in nephroblastoma in the absence of KIT, PDGFRalpha or EGFR mutations.

Partial fanconi syndrome induced by imatinib therapy: a novel cause of urinary phosphate loss

Imatinib mesylate (Gleevec, Glivec; Novartis, Basel, Switzerland) is a specific tyrosine kinase inhibitor that has become the gold-standard treatment for patients with chronic myeloid leukemia. Several tyrosine kinases inhibited by imatinib are expressed in the kidney, and although the drug is usually well tolerated, several cases of acute renal failure were reported. We describe for the first time a case of a patient treated by imatinib for chronic myeloid leukemia who developed partial Fanconi syndrome with mild renal failure, which leads to a discussion of the pathophysiological characteristics of imatinib-induced renal toxicity. Patients on long-term imatinib treatment should be monitored for renal failure, as well as proximal tubule dysfunction, including hypophosphatemia.

Concurrent occurrence of three primary neoplasms with different hystotype in the same kidney, associated with an adenoma of the omolateral adrenal gland: first case report

We present an unusual case of concurrent occurrence of three synchronous primary tumors in the same kidney (oncocytoma, chromophobe renal cell carcinoma, angiomyolipoma) associated to an adenoma of the omolateral adrenal gland in a patient with no evident clinical symptoms. The immunohistochemistry showed a positivity for KIT in oncocytoma and chromophobe cell carcinoma, and a weak positivity in the angiomyolipoma, only in the cells positive for HMB-45. This is the first report of this kind of presentation.

Targeted therapy for renal cell carcinoma: a new therapeutic paradigm

Renal cell carcinoma is the most common tumor of the kidney. It has an unpredictable behavior and poor response to systemic therapy. Developing newer therapy for this disease is a priority considering the high recurrence rate and the small subset of patients who benefit from the use of cytokines such as interferon-alpha or interleukin-2. Identifying molecular targets and targeting various biomarkers has revolutionized the therapeutic approach to advanced and metastatic renal cell carcinoma. Although some of the antiangiogenic agents and receptor tyrosine kinase inhibitors appear promising, further understanding of their mechanism of action and the patient population who would benefit most from such agents is still being explored. As numerous targeted agents are entering the clinical investigation arena in a relatively short period of time, newer challenges in renal cell carcinoma therapeutics are emerging. Some of the future challenges in using targeted antineoplastic agents in renal cell carcinoma will include evaluating their long-term safety and benefit, using the particular drug in the appropriate patient population after appropriate stratification and studying the combination of some of these drugs for synergy or additive effects.