Identification of the genes for kidney cancer: opportunity for disease-specific targeted therapeutics

mTOR pathway in renal cell carcinoma

After decades of therapeutic nihilism in the treatment of advanced renal cell carcinoma, remarkable therapeutic strides have been made over the last few years. Early forays into molecularly targeted therapy for this difficult-to-treat disease were based around the inhibition of gene products of the hypoxia-inducible factor (HIF) transcription factor (i.e., VEGF). Recent data suggest that inhibition of mTOR results in clinical benefit in patients with poor prognostic features, and in preclinical models this therapeutic effect involves downregulation of HIF. Intriguingly, patients with nonclear cell histology appeared to obtain clinical benefit when treated with mTOR inhibitors. This review will highlight the mTOR pathway, its relevance to both clear cell and nonclear cell renal cell carcinoma, and its place in the host of quickly expanding treatment options.

BHD mutations, clinical and molecular genetic investigations of Birt-Hogg-Dubé syndrome: a new series of 50 families and a review of published reports

BACKGROUND

Birt-Hogg-Dubé syndrome (BHDS) (MIM 135150) is an autosomal dominant predisposition to the development of follicular hamartomas (fibrofolliculomas), lung cysts, spontaneous pneumothorax, and kidney neoplasms. Germline mutations in BHD are associated with the susceptibility for BHDS. We previously described 51 BHDS families with BHD germline mutations.

OBJECTIVE

To characterise the BHD mutation spectrum, novel mutations and new clinical features of one previously reported and 50 new families with BHDS.

METHODS

Direct bidirectional DNA sequencing was used to screen for mutations in the BHD gene, and insertion and deletion mutations were confirmed by subcloning. We analysed evolutionary conservation of folliculin by comparing human against the orthologous sequences.

RESULTS

The BHD mutation detection rate was 88% (51/58). Of the 23 different germline mutations identified, 13 were novel consisting of: four splice site, three deletions, two insertions, two nonsense, one deletion/insertion, and one missense mutation. We report the first germline missense mutation in BHD c.1978A>G (K508R) in a patient who presented with bilateral multifocal renal oncocytomas. This mutation occurs in a highly conserved amino acid in folliculin. 10% (5/51) of the families had individuals without histologically confirmed fibrofolliculomas. Of 44 families ascertained on the basis of skin lesions, 18 (41%) had kidney tumours. Patients with a germline BHD mutation and family history of kidney cancer had a statistically significantly increased probability of developing renal tumours compared to patients without a positive family history (p = 0.0032). Similarly, patients with a BHD germline mutation and family history of spontaneous pneumothorax had a significantly increased greater probability of having spontaneous pneumothorax than BHDS patients without a family history of spontaneous pneumothorax (p = 0.011). A comprehensive review of published reports of cases with BHD germline mutation is discussed.

CONCLUSION

BHDS is characterised by a spectrum of mutations, and clinical heterogeneity both among and within families.

Genetic Counseling in Renal Masses

All urologists have faced patients suffering a renal cancer asking for the occurrence of the disease in their offspring and very often the answer to this question has not been well founded from the scientific point of view, and only in few cases a familial segregation tree is performed. The grate shift seen in the detection of small renal masses and renal cancer in the last decades will prompt us to know the indications for familial studies, which and when are necessary, and probably to refer those patients with a suspected familial syndrome to specialized oncological centers where the appropriate molecular and familial studies could be done. Use of molecular genetic testing for early identification of at-risk family members improves diagnostic certainty and would reduce costly screening procedures in at-risk members who have not inherited disease-causing mutations. This review will focus on the molecular bases of familial syndromes associated with small renal masses and the indications of familial studies in at-risk family members.

Hereditäre Nierentumoren

Etwa 1–4% aller Nierentumoren sind mit spezifischen Keimbahndefekten assoziiert. Nierentumoren sind sehr heterogen. Eine neue histogenetische Klassifikation beruht auf pathomorphologischen wie auch auf genetischen Kriterien. Für jede der 4 häufigsten Tumortypen besteht ein Bezug zu einer hereditären Form bzw. den jeweils betroffenen Genen. Bis heute sind mindestens 10 hereditäre Konditionen bekannt, bei denen Nierentumoren auftreten. Dieser Review stellt die heute zur Verfügung stehenden Möglichkeiten einer individuellen Betreuung von Patienten mit diesen seltenen syndromalen und nichtsyndromalen hereditären Formen dar.

Hereditary urological cancer syndromes

Hereditary urological cancer syndromes are rare, but it is important that they are recognized because they have important prognostic implications; prompt diagnosis can dramatically improve patient outcomes. The urologist or urological oncologist should, therefore, ascertain which tumors of the many seen in clinical practice warrant referral for the opinion of a clinical geneticist. Despite the aggressive natural history of most inherited urological cancer syndromes, organ-preserving treatments are desirable because these syndromes predispose affected patients to the formation of multifocal and metachronous tumors. Identification of the molecular mechanisms that underlie carcinogenesis in both familial and sporadic urological cancers has, in some cases, resulted in novel and specifically targeted approaches to therapy. Patients who present with early-onset or multiple tumors should be carefully investigated for the presence of a hereditary cancer syndrome, and once a diagnosis is made, appropriate screening should be instigated for family members to enable early detection of tumors both within and outside the urogenital tract.