Only two cases to date of t(2;2)(p22;p22) or del(2)(p22p22) LTBP1/BIRC6 in solid tumors, without further data; it has been described in a case of breast carcinoma, and in a case of lung squamous cell carcinoma (Yoshihara et al., 2015). Note: t(2;2)(p22;p22) or del(2)(p22p22) LTBP1/BIRC6 in acute myeloid leukemia has also been found found in two cases.

Invasive breast cancer is the most common carcinoma in women, accounting for 22% of all female cancers. One million women worldwide are diagnosed with breast cancer every year (Carcangiu et al. 2005).

The most common histologic type of invasive breast carcinoma is designated as ductal carcinoma (80% of all cases), with many morphologic variants. Invasive lobular carcinoma is the second major type (5-10%) of breast cancer (Carcangiu et al. 2005).

Squamous cell carcinoma is the most frequent lung cancer in male patients, representing about 40% of the cases, and only 25% in women (much less frequent in female patients than adenocarcinoma). Squamous cell carcinoma is the lung cancer the most often associated with tobacco smoking. Location of the tumour is usually central, present as a perihilar mass, with or without lobar collapse and obstructive pneumonitis, but it can also be peripheral at times.

There are small cell variants (differential diagnosis: SCLC), clear cell variants, well-differentiated papillary variants, basaloid variants with a very aggressive clinical course, and spindle cell (sarcomatoid) carcinosarcoma variants of the typical squamous cell carcinoma. The expression of cytokeratins (CK) CK5/6, CK34BE12 and TP63 (3q28, also called P63) are strong in squamous cell carcinoma, whereas the expression of CK7 and NKX2-1 (14q13, also called TTF-1) are strong in adenocarcinoma (Xu et al., 2014).

BIRC6 (Baculoviral IAP repeat-containing 6)

2p22.3

BIRC6 contains two domains: a N-terminal BIR repeat (needed for interactions with caspases and IAP-binding motif (IBM) containing proteins) and a C-terminal UBC domain (which can form a thiolester linkage with ubiquitin transferred by E1).
Inhibitor of apoptosis: BIRC6 is a peripheral membrane protein of the trans-Golgi network that protects cells from apoptosis
BIRC6 and treatment resistance: Silencing of BIRC6 has been shown to sensitize cancer cells to various anticancer agents
BIRC6 is essential in embryonic development.
Regulator of cytokinesis: BIRC6 is a major regulator of abscission, the final stage of cytokinesis.
Regulator of mitosis: BIRC6 interacts with CCNA2 (cyclin A) and promotes its degradation in early mitosis
BIRC6 and autophagy: BIRC6 is required to inhibit autophagy
(Iris Luk and Wang, 2014).
BIRC6 is involved in myelodysplastic syndromes and acute myeloid leukemias, colorectal cancer, neuroblastoma, skin melanoma, non-small cell lung cancer, prostate cancer, ovarian cancer, hepatocellular carcinoma and breast cancer.

LTBP1 (latent transforming growth factor beta binding protein 1)

2p22.3

Eleven splice variants.

1721 amino acids; belongs to the LTBP/fibrillin family.
LTBP1 is composed of a signal peptide: (amino acids 1-23), 18 epidermal growth factor (EGF)-like repeats and four cysteines rich domains, the TB (TGFb binding protein-like) domains. The LTBP1 C-terminus interacts with the extracellular matrix via fibrillin microfibrils. EGF-like repeats provide stability to the protein structure
TGFB1 is secreted as a biologically latent complex composed of LTBP1, a latency associated peptide (LAP), (LAP is the TGFB1 pro-peptide which regulates latency, that is cleaved intracellularly prior to secretion), and the TGFB1 cytokine. LTBP1 plays roles in facilitating the folding and secretion of TGFB1 from the cell, and activation.
LTBP1 interacts with FBN1 (fibrillin 1). This interaction allows LTBP1 to sequester TGFB1 to fibrillin microfibrils; EFEMP2 (EGF containing fibulin-like extracellular matrix protein 2, or fibulin4) and ADAMTSL proteins form ternary complexes with LTBP1 and fibrillin.
LTBP1 is involved in epithelial-mesenchymal interaction and epithelial differentiation (Mazzieri et al., 2005; Robertson et al., 2014).

5 LTBP1 - 3 BIRC6