CKD and risk of renal cell carcinoma: a causal association?

Renal Cell Carcinoma in End-Stage Kidney Disease and the Role of Transplantation

Kidney transplant patients have a higher risk of renal cell carcinoma (RCC) compared to non-transplanted end-stage kidney disease (ESKD) patients. This increased risk has largely been associated with the use of immunosuppression; however, recent genetic research highlights the significance of tissue specificity in cancer driver genes. The implication of tissue specificity becomes more obscure when addressing transplant patients, as two distinct metabolic environments are present within one individual. The oncogenic potential of donor renal tissue is largely unknown but assumed to pose minimal risk to the kidney transplant recipient (KTR). Our review challenges this notion by examining how donor and recipient microenvironments impact a transplant recipient's associated risk of renal cell carcinoma. In doing so, we attempt to encapsulate how ESKD-RCC and KTR-RCC differ in their incidence, pathogenesis, outcome, and approach to management.

Kidney Function and Risk of Renal Cell Carcinoma

BACKGROUND

We evaluated the temporal association between kidney function, assessed by estimated glomerular filtration rate (eGFR), and the risk of incident renal cell carcinoma (RCC). We also evaluated whether eGFR could improve RCC risk discrimination beyond established risk factors.

METHODS

We analyzed the UK Biobank cohort, including 463,178 participants of whom 1,447 were diagnosed with RCC during 5,696,963 person-years of follow-up. We evaluated the temporal association between eGFR and RCC risk using flexible parametric survival models, adjusted for C-reactive protein and RCC risk factors. eGFR was calculated from creatinine and cystatin C levels.

RESULTS

Lower eGFR, an indication of poor kidney function, was associated with higher RCC risk when measured up to 5 years prior to diagnosis. The RCC HR per SD decrease in eGFR when measured 1 year before diagnosis was 1.26 [95% confidence interval (95% CI), 1.16-1.37], and 1.11 (95% CI, 1.05-1.17) when measured 5 years before diagnosis. Adding eGFR to the RCC risk model provided a small improvement in risk discrimination 1 year before diagnosis with an AUC of 0.73 (95% CI, 0.67-0.84) compared with the published model (0.69; 95% CI, 0.63-0.79).

CONCLUSIONS

This study demonstrated that kidney function markers are associated with RCC risk, but the nature of these associations are consistent with reversed causality. Markers of kidney function provided limited improvements in RCC risk discrimination beyond established risk factors.

IMPACT

eGFR may be of potential use to identify individuals in the extremes of the risk distribution.

The relationship between blood pressure and risk of renal cell carcinoma

BACKGROUND

The relation between blood pressure and kidney cancer risk is well established but complex and different study designs have reported discrepant findings on the relative importance of diastolic blood pressure (DBP) and systolic blood pressure (SBP). In this study, we sought to describe the temporal relation between diastolic and SBP with renal cell carcinoma (RCC) risk in detail.

METHODS

Our study involved two prospective cohorts: the European Prospective Investigation into Cancer and Nutrition study and UK Biobank, including >700 000 participants and 1692 incident RCC cases. Risk analyses were conducted using flexible parametric survival models for DBP and SBP both separately as well as with mutuality adjustment and then adjustment for extended risk factors. We also carried out univariable and multivariable Mendelian randomization (MR) analyses (DBP: ninstruments = 251, SBP: ninstruments = 213) to complement the analyses of measured DBP and SBP.

RESULTS

In the univariable analysis, we observed clear positive associations with RCC risk for both diastolic and SBP when measured ≥5 years before diagnosis and suggestive evidence for a stronger risk association in the year leading up to diagnosis. In mutually adjusted analysis, the long-term risk association of DBP remained, with a hazard ratio (HR) per standard deviation increment 10 years before diagnosis (HR10y) of 1.20 (95% CI: 1.10-1.30), whereas the association of SBP was attenuated (HR10y: 1.00, 95% CI: 0.91-1.10). In the complementary multivariable MR analysis, we observed an odds ratio for a 1-SD increment (ORsd) of 1.34 (95% CI: 1.08-1.67) for genetically predicted DBP and 0.70 (95% CI: 0.56-0.88) for genetically predicted SBP.

CONCLUSION

The results of this observational and MR study are consistent with an important role of DBP in RCC aetiology. The relation between SBP and RCC risk was less clear but does not appear to be independent of DBP.

Kidney Cancer and Chronic Kidney Disease: Too Close for Comfort

Kidney cancer and chronic kidney disease are two renal pathologies with very different clinical management strategies and therapeutical options. Nonetheless, the cellular and molecular mechanisms underlying both conditions are closely related. Renal physiology is adapted to operate with a limited oxygen supply, making the kidney remarkably equipped to respond to hypoxia. This tightly regulated response mechanism is at the heart of kidney cancer, leading to the onset of malignant cellular phenotypes. Although elusive, the role of hypoxia in chronic kidney diseases is emerging as related to fibrosis, a pivotal factor in decaying renal function. The present review offers a perspective on the common biological traits shared between kidney cancer and chronic kidney disease and the available and prospective therapies for both conditions.

Associations Between Kidney Function, Proteinuria, and the Risk of Kidney Cancer: A Nationwide Cohort Study Involving 10 Million Participants

Chronic kidney disease in its later stages is associated with increased risk of kidney cancer. We investigated whether chronic kidney disease at milder stages is associated with increased kidney cancer risk, using a retrospectively selected cohort of 9,809,317 adults in the Republic of Korea who participated in a nationwide health screening (2009-2016). We examined the impact of estimated glomerular filtration rate (eGFR), dipstick proteinuria, and interactive associations between the 2 factors on the risk of incident kidney cancer. During a median follow-up period of 7.3 years, 10,634 kidney cancers were identified. After adjustment for multiple confounders, participants with a reduced eGFR had an increased risk of kidney cancer (for eGFR <30 mL/minute/1.73 m2, adjusted hazard ratio = 1.18 (95% confidence interval: 1.01, 1.39); for eGFR 30-59 mL/minute/1.73 m2, adjusted hazard ratio = 1.22 (95% confidence interval: 1.14, 1.31)) compared with those with an eGFR of 60-89 mL/minute/1.73 m2. A dose-response relationship between the severity of proteinuria and incident kidney cancer was observed. Analyses of joint effects of eGFR and dipstick proteinuria showed that with the presence of proteinuria, kidney cancer incidence was markedly increased along with decreasing eGFR. Reduced eGFR and proteinuria are significantly associated with subsequent risk of kidney cancer, possibly in a synergistic manner.

Bioinformatic gene analysis for possible biomarkers and therapeutic targets of hypertension-related renal cell carcinoma

BACKGROUND

Renal cell carcinoma (RCC) is one of the most prevalent malignant tumors of the urinary system. Hypertension can cause hypertensive nephropathy (HN). Meanwhile, Hypertension is considered to be related to kidney cancer. We analyzed co-expressed genes to find out the relationship between hypertension and RCC and show possible biomarkers and novel therapeutic targets of hypertension-related RCC.

METHODS

We identified the differentially expressed genes (DEGs) of HN and RCC through analyzing Gene Expression Omnibus (GEO) datasets GSE99339, GSE99325, GSE53757 and GSE15641 by means of bioinformatics analysis, respectively. Then we evaluated these genes with protein-protein interaction (PPI) networks, Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and CTD database. Subsequently, we verified co-expressed DEGs with Gene Expression Profiling Interactive Analysis (GEPIA) database. Finally, corresponding predicted miRNAs of co-expressed DEGs were identified and verified via mirDIP database and Starbase, respectively.

RESULTS

We identified 9 co-expressed DEGs, including BCAT1, CORO1A, CRIP1, ESRRG, FN1, LYZ, PYCARD, SAP30, and PTRF. CRIP1 and ESRRG and their corresponding predicted miRNAs, especially hsa-miR-221-5p, hsa-miR-205-5p, hsa-miR-152-3p and hsa-miR-137 may be notably related to hypertension-related RCC.

CONCLUSIONS

CRIP1 and ESRRG genes have great potential to become novel biomarkers and therapeutic targets concerning hypertension-related RCC.

Renal Cell Carcinoma in Renal Transplantation: The Case for Surveillance

INTRODUCTION

Between January 2013 and September 2015, 135 consecutive renal transplant patients were screened prospectively with ultrasound for renal cell carcinoma (RCC).

RESULTS

Eighteen ultrasound abnormalities were identified with 4 solid lesions detected. Fifty-six other patients were screened retrospectively by referring nephrology groups, with 6 additional malignancies found.

CONCLUSION

As a result of our data, we recommend and have instituted annual ultrasound screening of native kidneys in all renal transplant patients.

Transcriptomic changes in human renal proximal tubular cells revealed under hypoxic conditions by RNA sequencing

Chronic hypoxia often occurs among patients with chronic kidney disease (CKD). Renal proximal tubular cells may be the primary target of a hypoxic insult. However, the underlying transcriptional mechanisms remain undefined. In this study, we revealed the global changes in gene expression in HK‑2 human renal proximal tubular cells under hypoxic and normoxic conditions. We analyzed the transcriptome of HK‑2 cells exposed to hypoxia for 24 h using RNA sequencing. A total of 279 differentially expressed genes was examined, as these genes could potentially explain the differences in HK‑2 cells between hypoxic and normoxic conditions. Moreover, 17 genes were validated by qPCR, and the results were highly concordant with the RNA seqencing results. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed to better understand the functions of these differentially expressed genes. The upregulated genes appeared to be significantly enriched in the pathyway of extracellular matrix (ECM)-receptor interaction, and in paticular, the pathway of renal cell carcinoma was upregulated under hypoxic conditions. The downregulated genes were enriched in the signaling pathway related to antigen processing and presentation; however, the pathway of glutathione metabolism was downregulated. Our analysis revealed numerous novel transcripts and alternative splicing events. Simultaneously, we also identified a large number of single nucleotide polymorphisms, which will be a rich resource for future marker development. On the whole, our data indicate that transcriptome analysis provides valuable information for a more in depth understanding of the molecular mechanisms in CKD and renal cell carcinoma.

Efficacy and Toxicity of Mammalian Target Rapamycin Inhibitors in Patients with Metastatic Renal Cell Carcinoma with Renal Insufficiency: The Korean Cancer Study Group GU 14-08

Purpose

We evaluated the efficacy and toxicity of mammalian target rapamycin inhibitors in Korean patients with metastatic renal cell carcinoma (mRCC) with chronic renal insufficiency not requiring dialysis.

Materials and Methods

Korean patients with mRCC and chronic renal insufficiency not requiring dialysis treated with everolimus or temsirolimus between January 2008 and December 2014 were included. Patient characteristics, clinical outcomes, and toxicities were evaluated. Overall survival (OS) and progression-free survival (PFS) durations were evaluated according to the degree of renal impairment.

Results

Eighteen patients were considered eligible for the study (median age, 59 years). The median glomerular filtration rate was 51.5 mL/min/1.73 m². The best response was partial response in six patients and stable disease in 11 patients. The median PFS and OS durations were 8 months (95% confidence interval [CI], 0 to 20.4) and 32 months (95% CI, 27.5 to 36.5), respectively. The most common non-hematologic and grade 3/4 adverse events included stomatitis, fatigue, flu-like symptoms, and anorexia as well as elevated creatinine level.

Conclusion

Mammalian target rapamycin inhibitors were efficacious and did not increase toxicity in Korean patients with mRCC and chronic renal insufficiency not requiring dialysis.

The use of lineage tracing to study kidney injury and regeneration

Lineage tracing is a powerful tool to track cells in vivo and provides enhanced spatial, temporal, and kinetic resolution of the mechanisms that underlie tissue renewal and repair. The data obtained from novel mouse models engineered for lineage tracing has started to transform our understanding of the changes in cell fate that underlie renal pathophysiology, the role of stem and/or progenitor cells in kidney development, and the mechanisms of kidney regeneration. The complexity of the genetic systems that are engineered for lineage tracing requires careful analysis and interpretation. In this Review we emphasize that close attention in lineage tracing studies must be paid to the specificity of the promoter, the use of drug-controlled activation of Cre recombinase as a genetic switch, and the type of reporter that should be engineered into lineage tracing genetic constructs. We evaluate the optimal experimental conditions required to achieve the pre-specified aims of the study and discuss the novel genetic techniques that are becoming available to study putative renal progenitor cells and the mechanisms of kidney regeneration.