Desmocollin-3 [DSC3] is a transmembrane glycoprotein belonging to cadherin family of homophilic adhesion molecules, and is produced
by the endoplasmic reticulum. DSC3 expression is seen in the suprabasal layer of stratified epithelium. DSC3 is a p53 responsive gene and
can be detected by microarray. DSC3 protein expression is associated with expression of wild type p53 expression and can be detected by
immune histochemistry. DSC3 protein is expressed on the surface of normal tissues. In proliferative tissues like, fetal and cancer, DSC3 protein
is also seen in cytoplasm besides on cell surface. Expression of DSC3 is used as a diagnostic biomarker to differentiate squamous NSCLC from
adenocarcinoma of lung. DSC3 expression is also seen in ovarian cancer, melanoma, colorectal cancer, cervical cancer, and meningioma cancer
arising from oral cavity.
Expression of wild type p53 is associated with expression of DSC3. Chemotherapy, radiotherapy, targeted therapy [tyrosine kinase
inhibitors], hypo methylating agents are known to induce expression of DSC3 in DSC3 negative cancers. As a homophilic adhesion molecule, it
provides a unique opportunity for active immunotherapy by inducing DSC3 on surface of immune cells. CADI-05 is one such immunotherapy. It
is found useful in management of squamous NSCLC and ovarian cancer when used with chemotherapy. It improves response rate and survival.
As a mono therapy, it induces remission in melanoma and bladder cancer.
Desmocollin-3[DSC3] is one of the adhesion molecules of cadher
in super family found in desmosome and is a major adhesive force of
epithelial cells [1-6]. DSC3 is a transmembrane calcium-dependent
glycoprotein produced by the endoplasmic reticulum,encoded by
the DSC3 gene. DSC3 is expressed, mainly in basal and immediate
suprabasal layers of the stratified squamous epithelia [7] like buccal
mucosa, esophagus, cervix, fore skin tongue, trachea etc. [3,8]. As
an adhesion molecule, DSC3 provides homophilic adhesion i.e. cells
expressing DSC3 will adhere to each other at the site of expression
but not with others; it also works as a receptor as well as ligand to
participate in cell signaling [9].
P53 and Desmocollin-3
DSC3 is one of the p53-responsive gene [1-11]. p53 is reported
to be an upstream to DSC3. Expression of DSC3 gene is associated
with expression of wild type of p53 and depends on the methylation
status of the DSC3 DNA in the p53 binding site [10,11]. p53
expression in cancer is known to be altered by mutation or deletion
of the p53 gene, with mutation of p53 being the most common
event in human cancer [12]. Besides deletion and mutation of
p53, p53 target genes are also silenced by epigenetic silencing like
DNA methylation [1-11]. Mutant p53 inactivates p63 and is also
associated with down regulation of DSC3 [10]. p63 is a master
regulator of epidermal gene transcription and plays an essential
function in controlling epidermal development , cell proliferation,
stratification and cell–matrix adhesion [13]. There are two main
isoforms of p63, Tap63 and Delta Np63. Delta Np63 alpha isoform
is the most abundantly expressed p63 isoform. Both p63 and delta
Np63 are activator for desmocollin-3 gene [13]. Knockdown of p63
and delta Np63 results in marked reduction in expression of DSC3
without any effect on expression of another adhesion molecule
E-cadherin [13].
Desmocollin-3 and Cancer:
Desmosomal abnormalities are seen in cancer, as are alterations
in DCS3 expression. In many epithelial cancers, DSC3 expression
either over expressed or absent. DSC3 expression is not seen in
many cancers e.g. adenocarcinoma of lung, breast, prostate cancer
wherein there is mutation of P53 or hyper methylation. DSC3 was
first cloned from human bladder cancer cell line [14]. Its presence
can be detected by microarray (gene) or immunehistochemistry
(protein)
a. Lung Cancer:DSC3 is not seen in normal lung tissue
[15]. DSC-3 gene is over expressed 58 fold compared to
adenocarcinoma [16]. Immunohistochemistry reveals in lung
cancer expression of DSC3 is seen at basal layers of tumor. DSC3expression is seen in around 30% of cases [17]. DSC 3 expression
is seen in squamous NSCLC and not in adenocarcinoma of lung.
It is closely associated with p63 expression which is another
marker used for differentiation of Squamous NSCLC from other
varieties [18-20].
b. OvarianCancer: DSC3 is seen in around 85% of ovarian
caners. Its expression seems to be dependent on FSH.
c. Melanoma: DSC3 is expressed in melanoma [21-24]. Its
expression decreases with increased thickness and progression
to metastatic melanoma [22].
c. Melanoma: DSC3 expression is seen in 60% colon
cancer and also seen in 40% of colorectal lesion metastatic to
the liver [10,25,26].
e. Bladder Cancer: DSC3 was first cloned from a bladder
cancer cell line [14]. We have documented DSC3 expression in
around 60% of bladder cancer irrespective of grade and stage
of tumor.
f. Meningioma: DSC3 expression is described in around
60% of meningioma [21,27].
g. Chondrosarcoma: DSC3 gene expression is detected in 4
of the 5 chondrosarcoma cell lines [28].
h. Pediatric Acute Lymphoblastic Leukemia: DSC3 gene
is described to be over expressed in all TEL-AML1 subtype of
paediatric acute lymphoblastic leukemia [29].
i. Skin Tumors: Loss of DSC3 is seen with tumour
development and progression [30] and is associated with
increase in K-Ras induced skin tumors [31].
j. Oral squamous cell carcinoma: Oral mucosa normally
expresses DSC3. However development of oral Squamous cell
carcinoma is associated with reduction or absence of DSC3
expression. This reduction/absence of DSC3 expression was
associated with higher histological grade (moderately or poorly
differentiated) [32].
k. Breastcancer: DSC3 is expressed in a normal breast
but is down-regulated in breast cancer cell lines and primary
breast tumors at protein as well as gene level [3,33]. The
loss of DSC3protein expression is more likely to be aberrant
methylation of rather than gene deletion or gross rearrangement
of the gene [3].
l. Prostatecancer: DSC3 is expressed in normalprostate as
well asbenign prostate tumors but is absent in prostate cancer
due to hyper methylation [34].
Table 1: Sensitivity of DSC3 for squamous NSCLC.
Desmocollin-3 as a diagnostic biomarker:
a. Squamous NSCLC: DSC3 is used as a diagnostic biomarker
to differentiate Squamous NSCLC from adenocarcinoma of
lung [35-42]. DSC3 is more specific for squamous NSCLC
compared to p63 as p63 is also expressed in Adenocarcinoma.
DSC3 gene is up-regulated in squamous NSCLC and down
regulated in adenocarcinoma [43]. Specificity of DSC3 is 100%
while sensitivity is variable [18-20, 44,45] and varies with
differentiation of tumor. Maximum sensitivity is seen in highly
differentiated tumors and is lowest for poorly differentiated
Squamous NSCLC. Sensitivity of DSC3 for squamous NSCLC
is 93.2% in large cohort of 426 but drops to 59% in poorly
differentiated squamous NSCLC (Table 1). DSC3 expression in
NSCLC is also not related to stage or histologic grade [17] of a
disease [46].
b. Paediatric Acute Lymphoblastic Leukaemia: DSC3
gene expression can be used to differentiate TEL-AML1 from
other subtypes of paediatricacute lymphoblastic leukaemia
[29].
a) NSCLC: In spite of squamous NSCLC having poor
prognosis,smaller clinical trials suggest that DSC3 expressing
tumors are likely to have better survival compared to DSC3
negative tumors and may serve as a potential prognostic
marker [1,17].
b) Colorectalcancer: Tumors with methylated DSC3 DNA
were significantly correlated to a worse clinical outcome than
unmethylated tumors. The methylation status of DSC3 DNA was
not linked to any of clinical pathological parameters includingage, gender, size of tumor, tumor grading, and tumor stage in
these patients [10].
c) Prostatecancer: Loss of DSC3 predicts poor prognosis.
Effect of therapeutic intervention on DSC3 expression:
a. DNA damaging agents: Expression of wild type of p53
can also be increased or induced by DNA damaging agents like
radiotherapy, doxorubicin, cisplatin, paclitaxel, gemcitabine etc.
Expressionof wild type p53 is sufficient to induce expression
of DSC3 in breast, colorectal and lung cancers in absence of
DSC3 DNA methylation [1,10,11]. Expression of wild typep53
converts DSC3 negative tumors in to DSC3 positive.
b. Tyrosine Kinase inhibitors: DSC3 expression has
reciprocal relationship with ERK of MAPK family.Decreased
ERK is seen following successful treatment with tyrosine kinase
inhibitors. EGFR inhibitor like gefitinib converts DSC3 negative
EGFR mutant adenocarcinoma of lung in to DSC3 positive.
c. Hypomethylating/Demethylating agents: DSC3
hypermethylation is seen in prostate and breast cancerleading
to lack of DSC3 expression by this tumors [3, 6, 33].
Hypomethylating/Demethylating agents like azacytidine
convert DSC3 negative tumors to DSC3 Cadi-05[3,47].
Desmocollin-3 and immunotherapy:
DSC3 is a homophilic adhesion molecule, which works as a
receptor as well as a ligand. This provides an opportunity to develop
an active immunotherapy for DSC3 expressing tumors by inducing
DSC3 on surface of tumor targeting activated immune cells. CADI-
05 is one such active immunotherapy. It induces DSC3 expression
on immune cells and also induces Th1 type of immune response
through TLR2 agonist activity [48]. Cadi-05 increases tumor
infiltrating immune cells [49] and found useful in management
of cancers as a monotherapy for small size tumors [49,50]. As
combination therapy with checkpoint modulators, radiotherapy
as well as chemotherapy, Cadi-05 improves outcome of large size
tumors [51].
Cadi-05 achieves and maintains remission in melanoma as
well as in bladder cancer as a systemic monotherapy [52, 53].
In combination with chemotherapy, it improves response rate.
Responses achieved are durable and results in improved survival.
Identical results are seen when combined with radiotherapy. It is
expected that combination with anti PD-L1 therapy will result in
significant improvement in no. of durable responses.
ISSN: 2574 -1241
Abstract
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