BIRC7 Human

What is BIRC7 and what is its molecular function in human cells?

BIRC7 belongs to the inhibitors of apoptosis proteins (IAP) family. It contains a BIR domain that has been shown to bind and inhibit caspases-3, -7, and -9, playing a key role in inhibiting apoptosis . BIRC7 is predominantly expressed in fetal tissues and most solid tumors in humans, with minimal expression in normal adult tissues . The protein functions primarily by preventing activation of the apoptotic cascade, which contributes to tumor cell survival under various stress conditions.

Methodologically, studies of BIRC7's molecular function typically employ:

• Recombinant protein expression systems

• Caspase activity assays

• Protein-protein interaction studies (co-immunoprecipitation, yeast two-hybrid)

• Cell viability and apoptosis assays following manipulation of BIRC7 expression

How is BIRC7 expression detected in research and clinical samples?

BIRC7 expression can be assessed at both protein and mRNA levels using multiple techniques:

• mRNA detection: qRT-PCR is commonly used to quantify BIRC7 transcript levels, as demonstrated in studies of adrenocortical carcinoma (ACC) where relative livin mRNA expression was significantly higher in ACC than in adenomas and normal adrenal glands (0.060 ± 0.116 vs 0.004 ± 0.014 and 0.002 ± 0.009, respectively, p < 0.01) .

• Protein detection: Immunohistochemistry (IHC) using highly specific antibodies against full-length recombinant human livin is effective for tissue samples . This approach has been used to detect BIRC7 in various cancers including:

  • 56% of extrahepatic cholangiocarcinoma (EHCC) cases

  • 31% of B-cell non-Hodgkin's lymphomas and 37% of T-cell non-Hodgkin's lymphomas

• Western blotting: For cell lines and fresh tissue samples, this technique provides quantitative assessment of BIRC7 protein levels and can distinguish between isoforms .

How does BIRC7 expression vary across different cancer types?

BIRC7 shows differential expression patterns across cancer types with significant implications for diagnosis and prognosis:

This pattern of expression suggests BIRC7 has potential utility as a biomarker for malignancy across multiple tumor types.

What is the relationship between BIRC7 expression and patient survival?

BIRC7 expression has been consistently associated with worse clinical outcomes across multiple cancer types:

Researchers investigating prognostic implications should consider multivariate analyses that account for established clinical parameters alongside BIRC7 expression.

How does hypoxia affect BIRC7 expression and function in cancer cells?

Hypoxia significantly upregulates BIRC7 expression through HIF-1α-dependent mechanisms:

• Transcriptome sequencing of melanoma cells exposed to hypoxia for 12 hours identified BIRC7 among the most significantly upregulated genes .

• Both mRNA and protein levels of BIRC7 increase substantially under hypoxic conditions, as confirmed by RT-qPCR and Western blot analyses .

• The addition of HIF-1α inhibitor reduces hypoxia-induced BIRC7 protein expression, confirming the regulatory relationship between these factors .

• Luciferase assays have demonstrated direct binding of HIF-1α to the BIRC7 promoter through a putative binding site, with significant increases in relative luciferase activity under hypoxic conditions .

Methodologically, researchers studying this relationship should:

• Establish reliable hypoxia models using hypoxic chambers (e.g., MACS VA500 microaerophilic workstation with 95% N2 and 5% CO2 atmosphere)

• Use both pharmacological HIF-1α inhibitors and genetic approaches (siRNA)

• Employ promoter-reporter assays to confirm direct transcriptional regulation

What is the functional role of BIRC7 in cancer cell response to hypoxia?

BIRC7 appears to be a critical mediator of hypoxia-induced cancer cell survival and invasiveness:

• Hypoxia promotes proliferation and invasion while inhibiting apoptosis in melanoma cell lines (A875 and M14) .

• Knockdown of BIRC7 expression under hypoxic conditions effectively blocks these hypoxia-induced effects on cancer cell behavior .

• Specifically, siRNA-mediated BIRC7 knockdown:

  • Reduces cell proliferation (as measured by CCK-8 assay)

  • Increases apoptosis (as measured by flow cytometry)

  • Decreases cell invasion capability

This suggests BIRC7 is not merely induced by hypoxia but actively contributes to hypoxia-mediated tumor promotion, making it a potential therapeutic target for hypoxic tumors.

What experimental approaches have proven effective for BIRC7 inhibition?

Several approaches have demonstrated efficacy in inhibiting BIRC7 in preclinical models:

• siRNA-mediated knockdown: The most commonly reported approach uses sequences such as 5′-GGTGAGGTGCTTCTTCTGC-3′ that effectively reduce BIRC7 expression in multiple cancer cell lines . This approach has demonstrated anti-tumor effects including:

  • Inhibition of cell proliferation

  • Induction of apoptosis

  • Reduction in invasive capacity

• HIF-1α inhibition: Since BIRC7 is a downstream target of HIF-1α, inhibitors of this transcription factor can indirectly reduce BIRC7 expression, particularly in hypoxic tumor environments .

• Small molecule inhibitors: While not specifically mentioned in the search results, IAP antagonists that target multiple IAP family members have shown promise in clinical development.

How does BIRC7 inhibition affect response to conventional cancer therapies?

BIRC7 inhibition appears to sensitize cancer cells to various therapeutic modalities:

• In glioblastoma, targeting BIRC7 has been shown to enhance the efficacy of both radiotherapy and chemotherapy .

• The anti-apoptotic function of BIRC7 suggests its inhibition may broadly sensitize cancer cells to therapies that induce apoptosis.

• Based on the finding that knockdown of BIRC7 reverses the effect of hypoxia on promoting tumor progression, combining BIRC7 inhibition with therapies targeting hypoxic cells may be particularly effective .

Researchers should consider combination approaches that target BIRC7 alongside conventional cytotoxic therapies or other targeted agents.

What are the optimal cell culture models for studying BIRC7 function?

Based on the available research, effective cell culture models include:

• Melanoma cell lines: A875 and M14 cells have been successfully used to study BIRC7 in the context of hypoxia and demonstrate clear phenotypic responses to BIRC7 manipulation .

• Hypoxia modeling: A chamber filled with 95% N2 and 5% CO2 effectively simulates hypoxia in melanoma cells. After hypoxia treatment for 12h, followed by oxygen restoration for 12h, experimental analyses can be performed .

• Transfection protocols: Lipofectamine 2000 reagent has been effectively used for siRNA delivery targeting BIRC7. Successful knockdown should be confirmed at both mRNA and protein levels .

For optimal results, researchers should:

• Maintain cells in DMEM supplemented with 10% FBS and 1% penicillin-streptomycin

• Plate cells at appropriate densities (e.g., 2000 cells per well for 96-well plates)

• Include appropriate controls for both normoxic and hypoxic conditions

What assays are most informative for assessing BIRC7's functional effects?

Multiple assays provide comprehensive assessment of BIRC7's role in cancer biology:

• Proliferation: CCK-8 assay effectively quantifies changes in proliferation following BIRC7 manipulation. Cells should be seeded at 2000 cells per well, treated as desired, incubated with CCK-8 solution for 2h, and measured at 450nm .

• Apoptosis: Flow cytometry with appropriate staining (e.g., Annexin V/PI) provides quantitative assessment of apoptotic populations following BIRC7 manipulation .

• Invasion: Transwell invasion assays can determine how BIRC7 affects invasive capacity of cancer cells .

• Protein-protein interactions: Luciferase reporter assays have successfully demonstrated HIF-1α binding to the BIRC7 promoter, with significant changes in activity between wild-type and mutated binding sites .

For comprehensive evaluation of BIRC7's role, researchers should employ multiple assays that assess different cellular processes affected by this protein.