C-kit overexpression is not associated with KIT gene mutations in chromophobe renal cell carcinoma or renal oncocytoma

Targeting KIT With Antibody-Drug Conjugates in Chromophobe Renal Cell Carcinoma

INTRODUCTION

Chromophobe renal cell carcinoma (ChRCC) is the third most common type of RCC. There are no proven therapies for patients with metastatic ChRCC, with a median survival of 27 months. KIT (CD117) is a membrane-associated tyrosine kinase receptor. Antibody-drug conjugates (ADC) targeting KIT were previously found to be safe and effective in preclinical models of KIT-positive cancers but have not been tested in ChRCC.

RESULTS

In The Cancer Genome Atlas, KIT mRNA expression is higher in ChRCC than any other tumor type with the mean expression 12 times higher than matched normal kidney. Of the 15 metastatic ChRCC specimens stained for KIT at our institution, 87% were positive. In single-cell RNA sequencing data, KIT and SCF, the KIT ligand, are co-expressed in ChRCC tumor cells. We found that KIT mRNA expression is significantly higher in ChRCC-derived cells compared to clear cell renal cell carcinoma (ccRCC)-derived cells and normal kidney cells. Western blot analysis confirmed KIT expression in 5 ChRCC cell lines. Despite high KIT expression, knockdown of KIT or treatment with KIT targeting tyrosine kinase inhibitors did not decrease ChRCC cell proliferation. LOP628, a KIT ADC, decreased the viability of the ChRCC-derived cells by ∼60% with no effect on ccRCC cells.

CONCLUSION

Together, these data demonstrate that KIT is a viable therapeutic target for antibody-drug conjugates in ChRCC, providing a foundation for further investigation into KIT-targeted therapies.

Smoking enhanced the expression of c-kit in chromophobe renal cell carcinoma

INTRODUCTION

Smoking is an important risk factor for inducing renal cell carcinoma (RCC), but its specific mechanism affecting the development of RCC remains to be elucidated. Chromophobe RCC (ChRCC) is a subtype of RCC. Many studies have shown smoking is closely associated with RCC occurrence and c-kit plays a critical role in the progression of RCC, however, few studies focus on ChRCC. This study investigated the molecular mechanism between smoking and the c-kit pathway in ChRCC.

METHODS

Differentially expressed genes (DEGs) were obtained from The Cancer Genome Atlas (TCGA) in ChRCC and the expression of KIT in ChRCC was analyzed through the TCGA database combined with Gene Expression Omnibus (GEO) and oncomine databases. Moreover, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses and Protein Protein Interaction (PPI) network analysis were performed to explore the function of KIT and correlated DEGs as well as its co-expression genes in ChRCC. Finally, ChRCC patient samples were used to verify the effect of smoking on the c-kit expression.

RESULTS

The results showed that KIT is one of the DEGs and plays a vital role in ChRCC tumorigenesis. Interestingly, the expression of c-kit in cancer tissues of 27 smoking patients was significantly higher than that of 25 non-smoking patients (p<0.05), which suggests smoking might enhance the expression of c-kit in ChRCC patients.

CONCLUSIONS

Our results demonstrate that smoking might play a pivotal role in the ChRCC tumorigenesis via a pathway related to c-kit, and provided new insight into the relationship between smoking and the c-kit pathway in ChRCC.

c-Kit Receptors as a Therapeutic Target in Cancer: Current Insights

c-Kit is a type III receptor tyrosine kinase (RTK) that has an essential role in various biological functions including gametogenesis, melanogenesis, hematopoiesis, cell survival, and apoptosis. c-KIT aberrations, either overexpression or loss-of-function mutations, have been implicated in the pathogenesis and development of many cancers, including gastrointestinal stromal tumors, mastocytosis, acute myeloid leukemia, breast, thyroid, and colorectal cancer, making c-KIT an attractive molecular target for the treatment of cancers. Therefore, a lot of effort has been put into investigating the utility of tyrosine kinase inhibitors for the management of c-KIT mutated tumors. This review of the literature illustrates the role of c-KIT mutations in many cancers, aiming to provide insights into the role of TKIs as a therapeutic option for cancer patients with c-KIT aberrations. In conclusion, c-KIT is implicated in different types of cancer, and it could be a successful molecular target; however, proper detection of the underlying mutation type is required before starting the appropriate personalized therapy.

Low-grade oncocytic renal tumor (LOT): mutations in mTOR pathway genes and low expression of FOXI1

Low-grade oncocytic renal tumor (LOT) is an emerging provisional entity, described as rare solid renal oncocytic/eosinophilic tumor sharing diffuse CK7 and negative CD117 immunoprofile. The links between LOT and other eosinophilic chromophobe like-renal cell carcinomas (RCC) are currently discussed. We sequenced tumoral DNA with a next generation sequencing panel for kidney cancer and carried out immunohistochemical analyses with CK7, CD117, SDHB, 4EBP1-P, S6K-P, and FOXI1 antibodies in a series of ten cases of LOT (9 females, 1 male; mean age at surgery: 66 years, 42.3 to 83.4) retrospectively diagnosed from a cohort of 272 tumors initially classified as chromophobe RCC (CHRCC). All LOT were single, without known hereditary predisposition, classified stage pT1 (70%), pT2 (20%) or pT3a (10%). Morphological features were similar to previous descriptions and clinical behavior was indolent for the six cases with available follow-up. We identified genetic variations in mTOR pathway related genes in 80% of cases, MTOR (7 cases) or TSC1 (1 case). Expression of FOXI1 was absent in all cases. In 9 LOT, 4EBP1-P and S6K-P were overexpressed, suggesting mTOR pathway activation.Our data highlights the major role of mTOR pathway in tumorigenesis of LOT mostly due to activating MTOR gene variations. Absence of FOXI1 expression is a strong argument to distinguish LOT from eosinophilic CHRCC and to bring them closer to other recently described FOXI1 negative eosinophilic-CHRCC like with MTOR/TSC mutations. Altogether, our data argue to consider LOT as a distinct entity with a favorable clinical outcome. However, in case of metastasis, an accurate diagnosis of LOT would be essential for the patient's management and could allow targeted therapy.

Non-clear cell renal carcinomas: Review of new molecular insights and recent clinical data

Non-clear cell renal cell carcinomas (nccRCC) represent a highly heterogeneous group of kidney tumors, consisting of the following subtypes: papillary carcinomas, chromophobe renal cell carcinoma, so-called unclassified carcinomas or aggressive uncommon carcinomas such as Bellini carcinoma, renal cell carcinoma (RCC) with ALK rearrangement or fumarate hydratase-deficient RCC. Although non-clear cell cancers account for only 15 to 30% of renal tumors, they are often misclassified and accurate diagnosis continues to be an issue in clinical practice. Current therapeutic strategy of metastatic nccRCC is based primarily on guidelines established for clear cell tumors, the most common subtype, however this approach remains poorly defined. To date, published clinical trials for all histological nccRCC subtypes have been collectively characterized into one group, in contrast to clear cell RCC, and given the small numbers of cases, the interpretation of study results continues to be challenging. This review summarizes the available literature for each nccRCC subtype and highlights the lack of supportive evidence from prospective clinical trials and retrospective studies. Future trials should evaluate treatment approaches which focus on a specific histological subtype and progress in treating nccRCC will be contingent on understanding the unique biology of their individual histologies.

Comprehensive Immunoprofiles of Renal Cell Carcinoma Subtypes

In recent years, renal epithelial tumors have been among the fastest reclassifying tumors, requiring updates to the tumor classification system. Nonetheless, immunohistochemistry (IHC) remains the most widely used tool for renal epithelial tumors. In this proposal, we aimed to create the most efficient IHC panel for categorizing the diverse subtypes of renal tumors, and to find out more specific immunohistochemical results in each subtype or each antibody. A total of 214 renal tumors were analyzed using 10 possible IHC markers to differentiate subtypes, including three major renal cell carcinoma (RCC) subtypes, clear-cell type (50 cases), papillary type (50 cases), and chromophobe type (20 cases), and minor subtypes (MiT RCC, 13 cases; collecting duct carcinoma, 5 cases; and oncocytoma, 10 cases). A triple immunomarker (cytokeratin 7 (CK7)-carbonic anhydrase IX (CAIX)- alpha-methylacyl-CoA racemase (AMACR)) panel is useful in particular high-grade clear-cell tumors. If IHC remains ambiguous, the use of an adjunctive panel can be suggested, including CD10, epithelial membrane antigen, cathepsin K, c-kit, hepatocyte nuclear factor 1-β, and E-cadherin. For an efficient immunohistochemical strategy for subtyping of RCC, we conclude that the CK7-CAIX-AMACR panel is the best primary choice for screening subtyping.

Clinicopathological characteristics of KIT and protein kinase C-δ expression in adenoid cystic carcinoma: comparison with chromophobe renal cell carcinoma and gastrointestinal stromal tumour

AIMS

KIT overexpression is frequently observed in adenoid cystic carcinomas (AdCCs), chromophobe renal cell carcinomas (ChRCCs), and gastrointestinal stromal tumours (GISTs). Persistent KIT activation has been reported to be mediated by protein kinase C (PKC)-δ in a subset of colon cancers with wild-type KIT overexpression, and by PKC-θ in GISTs with mutant KIT overexpression. To elucidate the clinical implications of PKC-δ and PKC-θ expression in KIT-expressing tumours, we investigated the expression of KIT, PKC-δ and PKC-θ in AdCCs and ChRCCs in comparison with GISTs.

METHODS AND RESULTS

KIT expression, PKC-δ expression and PKC-θ expression were analysed in whole sections from 41 AdCCs, 40 ChRCCs and 56 GISTs by immunohistochemistry. Membranous expression of KIT was found in 34 AdCCs and all ChRCCs, whereas cytoplasmic expression of KIT was found in 46 GISTs. In AdCCs, PKC-δ expression was associated with histological grade (P = 0.049), lymphovascular invasion (P = 0.004), perineural invasion (P = 0.002), and KIT positivity (P = 0.002). PKC-δ positivity was associated with shorter relapse-free survival (RFS) (P = 0.017) and a tendency for there to be shorter overall survival (OS) (P = 0.090) in patients with AdCCs. No clinicopathological associations were observed between PKC-δ and KIT expression in ChRCCs. In GISTs, PKC-θ expression was associated with higher mitotic count (P = 0.011) and high grade according to the modified National Institutes of Health criteria (P < 0.001). PKC-θ positivity was associated with shorter RFS (P = 0.016) and a tendency for there to be shorter OS (P = 0.051) in patients with GISTs.

CONCLUSIONS

PKC-δ expression is associated with KIT expression and the prognosis of patients with AdCCs, suggesting that PKC-δ may be a potential therapeutic target for AdCCs.

Expression and clinicopathological correlations of retinoid acid receptor responder protein 1 in renal cell carcinomas

AIM

To evaluate the expression and prognostic value of RARRES1 at protein level in renal cell carcinoma (RCC).

MATERIALS & METHODS

Expression profile of RARRES1 was analyzed in 903 documented RCC followed by clinicopathological correlations and survival analysis.

RESULTS

RARRES1 expression was seen in 72.5% of RCC. A stronger RARRES1 expression was seen in high grade compared with low grade RCC (p < 0.001). Logrank tests revealed shorter overall survival in RARRES1 positive RCC (p = 0.006) and in pT1/2 tumors with RARRES1 expression (p = 0.002).

CONCLUSION

The variable expression profile in low and high grade RCC may reflect and confirm the differences of previous gene expression analysis. There was a significant prognostic value of RARRES1 expression in patients with RCC, especially in pT1/2 tumors.