65 YEARS OF THE DOUBLE HELIX: Exploiting insights on the RET receptor for personalized cancer medicine

The focus of precision cancer medicine is the use of patient genetic signatures to predict disease occurrence and course and tailor approaches to individualized treatment to improve patient outcomes. The rearranged during transfection (RET) receptor tyrosine kinase represents a paradigm for the power of personalized cancer management to change cancer impact and improve quality of life. Oncogenic activation of RET occurs through several mechanisms including activating mutations and increased or aberrant expression. Activating RET mutations found in the inherited cancer syndrome multiple endocrine neoplasia 2 permit early diagnosis, predict disease course and guide disease management to optimize patient survival. Rearrangements of RET found in thyroid and lung tumors provide insights on potential disease aggressiveness and offer opportunities for RET-targeted therapy. Aberrant RET expression in a subset of cases is associated with tumor dissemination, resistance to therapies and/or poorer prognosis in multiple cancers. The potential of RET targeting through repurposing of small-molecule multikinase inhibitors, selective RET inhibitors or other novel approaches provides exciting opportunities to individualize therapies across multiple pathologies where RET oncogenicity contributes to cancer outcomes.

Cancer predisposing germline mutations in patients (pts) with urothelial cancer (UC) of the renal pelvis (R-P), ureter (U) and bladder (B).

4510 Background: Urothelial cancers (UC) are suspected to have a substantial hereditary component, but other than highly penetrant genes such as those in mismatch-repair pathway (e.g. MSH2) typically associated with R-P/U primaries, heritable gene mutations have not been systematically studied. We sought to investigate the prevalence of known cancer pre-disposing germline mutations in pts with UC originating from all sites within the urinary tract. Methods: Pts with R-P, U and B primaries, unselected for suspicion of inherited cancer syndrome, were prospectively enrolled from medical oncology and urology clinics to a germline sequencing protocol from June 2016 to January 2017. Germline gene analysis was performed in a CLIA-certified lab using a next generation sequencing (NGS) platform (MSK-IMPACT) that analyzes tumor-normal DNA pairs. The germline gene panel consisted of 76 genes associated with hereditary cancer predisposition. Results: As of January 24, 2017, 101 pts have NGS results available, with median age 63 (31-87), 76% male, 24% female. Primary sites were B (67%), R-P/U (31%), or both (3%). 73% had organ-confined disease and 27% had metastases. 8% had early onset (≤45 yrs at diagnosis), 10% had a family history of UC, 25% had documented non-UC cancers. 25 pathogenic or likely pathogenic (P-LP) mutations were identified in 22 patients. P-LP mutations were present in 29% of pts with R-P/U primaries and 18% of pts with B primaries. 12 DNA damage response gene alterations were found (4 CHEK2, 3 BRCA1, 2 BRCA2, 1 ATM, 1 BRIP1, 1 NBN) and 8 in Lynch syndrome associated genes (5 MSH2, 2 MSH6, 1 MLH1). Other mutations include 2 APC, 1 TP53, and 1 FH. Notably 3 pts had 2 alterations each ( MSH6/ APC, BRCA2/ APC, BRCA1/ CHEK2). 9/22 pts with P-LP mutations did not meet American College of Medical Genetics criteria for genetic screening. Conclusions: 22% of UC pts had a germline mutation in a cancer-associated gene. There was an unexpectedly high frequency of pts with DNA-repair pathway mutations. Active accrual is ongoing to define the full spectrum of alterations. These results have profound implications for genetic counseling and screening and further studies are warranted.

Discovery and prevalence of cancer-susceptibility germline mutations (Mts) in patients (Pts) with advanced renal cell carcinoma (aRCC).

4524 Background: About 5% of RCC is thought to be familial, but recent studies suggest this may be an underestimate (Int. J. Cancer;100:476). We studied the prevalence of germline cancer-susceptibility mts in pts with aRCC. Methods: Pts with aRCC (stage III or IV), unselected for suspicion of an inherited cancer syndrome, were offered germline testing for 76 cancer-associated genes between 10/2015 and 12/2016. Germline sequencing was done as part of MSK-IMPACT, a matched tumor-normal next-generation sequencing platform. Results: 203/213 pts accepted testing (median age 55, range 13-55) of whom 73% had clear cell RCC (ccRCC), 92% had metastases, 20% were early onset (≤46 yrs at diagnosis), 9% had a family history of RCC, 6% multifocal RCC at diagnosis, and 15% ≥2 primary malignancies. Pathogenic/likely pathogenic mts were found in 35 pts (17%): 12 (6%) with mts in genes associated with familial RCC; 10 (5%) mts in high/moderate penetrance genes not linked to RCC (Table).13 (6%) had mts in genes of low/uncertain penetrance or for autosomal recessive disease. Mts were present in 15% of ccRCC and 19% of non-ccRCC. Mts were not more common in pts with early onset, family history, multifocal RCC, or ≥2 malignancies (p>0.1 for each by Fisher’s exact test). Notably, 4/12 pts with mts in familial RCC genes did not meet the American College of Medical Genetics (ACMG) criteria for testing (1 each VHL, BAP1, SDHA, FH). Prevalence of CHEK2 mts was compared to population databases (ExAC); CHEK2 conferred a relative risk of 10.9 (p< 0. 002; CI=3.9-24.7) for RCC. Conclusions: 17% of aRCC pts had a germline mutation in a cancer-associated gene of which 33% of the high penetrance RCC germline mts were not identified using standard clinical criteria, providing rationale for broad testing. Once the increased risk is confirmed, CHEK2 should be included in RCC genetic testing. [Table: see text]

Primary Clear Cell Microcystic Adenoma of the Sinonasal Cavity: Pathological or Fortuitous Association?

Primary clear cell microcystic adenoma of the sinonasal cavity is rare. It has previously been described only as a VHL-associated tumour. Von Hippel-Lindau (VHL) syndrome is an inherited cancer syndrome characterised by an elevated risk of neoplasia including clear cell renal cell carcinoma (ccRCC), haemangioblastoma, and phaeochromocytoma. We describe the second reported case of a primary clear cell microcystic adenoma of the sinonasal cavity. The 39-year-old patient with VHL syndrome had previously undergone resection and ablation of ccRCC. He presented with epistaxis. Imaging demonstrated a mass in the ethmoid sinus. Initial clinical suspicion was of metastatic ccRCC. However, tumour morphology and immunoprofile were distinct from the previous ccRCC and supported a diagnosis of primary microcystic adenoma. Analysis of DNA extracted from sinonasal tumour tissue did not show loss of the wild-type allele at the VHL locus. Although this did not support tumour association with VHL disease, it was not possible to look for a loss-of-function mutation. The association of primary microcystic adenoma of the sinonasal cavity with VHL disease remains speculative. These lesions are benign but are likely to require regular surveillance. Such tumours may require repeated surgical excision.

Lst4, the yeast Fnip1/2 orthologue, is a DENN-family protein

The folliculin/Fnip complex has been demonstrated to play a crucial role in the mechanisms underlying Birt–Hogg–Dubé (BHD) syndrome, a rare inherited cancer syndrome. Lst4 has been previously proposed to be the Fnip1/2 orthologue in yeast and therefore a member of the DENN family. In order to confirm this, we solved the crystal structure of the N-terminal region of Lst4 from Kluyveromyces lactis and show it contains a longin domain, the first domain of the full DENN module. Furthermore, we demonstrate that Lst4 through its DENN domain interacts with Lst7, the yeast folliculin orthologue. Like its human counterpart, the Lst7/Lst4 complex relocates to the vacuolar membrane in response to nutrient starvation, most notably in carbon starvation. Finally, we express and purify the recombinant Lst7/Lst4 complex and show that it exists as a 1 : 1 heterodimer in solution. This work confirms the membership of Lst4 and the Fnip proteins in the DENN family, and provides a basis for using the Lst7/Lst4 complex to understand the molecular function of folliculin and its role in the pathogenesis of BHD syndrome.

Cowden’s syndrome

Cowden’s syndrome (OMIM 158350), named after Rachel Cowden, is an autosomal dominant inherited cancer syndrome characterized by multiple hamartomas involving organ systems derived from all three germ cell layers and a risk of breast and thyroid cancers (1, 2). Endocrinologists may make the diagnosis of Cowden’s syndrome when they are presented with these patients’ endocrine lesions, chief of which are multinodular goitre, thyroid adenomas, and epithelial thyroid cancer. The Cowden’s syndrome susceptibility gene, PTEN, is located on chromosome sub-band 10q23.3 (3, 4).

Hereditary Diffuse Gastric Cancer: Multidisciplinary Case Report with Review of the Literature

Hereditary diffuse gastric cancer (HDGC) is a rare, inherited cancer syndrome with at least one fourth of HDGC patients having an autosomal dominantly inherited mutation of CDH1 (E-Cadherin). Penetrance is relatively high (70–80% lifetime risk for gastric cancer). It is important for pathologists to recognize the syndrome's phenotype in early gastric lesions: patchy intramucosal signet ring cells often associated with pagetoid spread. Due to the insidious nature of this lesion, surveillance is limited and currently prophylactic gastrectomy is an option chosen by many HDGC patients. We present a case report from a multidisciplinary team of authors with a review of the literature that includes the updated guidelines for CDH1 genetic testing.