Tumour Necrosis Factor

Question 1

TNF family

Answer 1

Two regulatory factors:

• TNF-α (cachectin)
• TNF-β (lymphotoxin).

Question 2

Where are TNF-α & TNF-β located

Answer 2

Next to each other on human chromosome 6

Question 3

Most significant cellular source of TNF-α

Answer 3

Activated macrophages

Question 4

Biological responses induced by TNF-α include:

Answer 4

• Activation of specific and non-specific immunity to gram-negative bacteria
• induction/regulation of inflammation
• Selective cytotoxicity against a range of tumour cells
• Mediation of various pathological conditions - e.g. septic shock and anorexia

Question 5

What is the biologically inactive form of TNF?

Answer 5

Monomer

Question 6

What is the active form of TNF?

Answer 6

Homotrimer

Question 7

What is the function of metalloprotease in TNF synthesis?

Answer 7

To cleave the pro-peptide

Question 8

How is TNF biosynthesis regulated?

Answer 8

Both at the transcriptional and post-translational levels

Question 9

What is the reason for constitutive expression of TNF-α mRNA in macrophages?

Answer 9

To be always ready as a first responder

Question 10

What is the origin of the interest in TNF-α and its naming?

Answer 10

Its anti-tumour activity

Question 11

Who was the American doctor who noted tumour regression in some cancer patients after they suffered a severe bacterial infection?

Answer 11

William Coley

Question 12

What was the approach to treating cancer that involved injecting bacteria into the tumour?

Answer 12

Direct bacterial injection

Question 13

Why was the approach of directly injecting bacteria into the tumour to treat cancer abandoned?

Answer 13

More often than not, the patient succumbed to the bacterial infection before being ‘cured’ of their cancer.

Question 14

How does TNF-α mediate death of sensitive cells

Answer 14

Apoptosis

• cellular shrinking, formation of dense ‘apoptoic’ masses and DNA fragmentaion

Necrosis

• Clumping of the nuclear chromatin, cellular swelling, disintrigation of intracellular organelles and cell lysis.

Question 15

Why has the initial interest in TNF as a general anti-cancer agent diminished?

Answer 15

• many tumours are not susceptible to destruction mediated by TNF
• tumour cell necrosis is not TNF’s major biological activity
• severe side effects accompany systemic administration of therapeutically relevant doses.

Question 16

What is Beromun?

Answer 16

A therapeutic agent based on TNF-α.

Question 17

How is Beromun produced?

Answer 17

It is human TNF-α-1a heterologously expressed by E. coli.

Question 18

What is the indication for the use of Beromun?

Answer 18

Treatment of soft-tissue sarcoma (STS) in the limbs, mainly to prevent or delay amputation.

Question 19

What is the usual combination therapy for Beromun?

Answer 19

The chemotherapeutic drug melphalan.

Question 20

What do clinical trials reveal about Beromun?

Answer 20

It delays/prevents the need for whole limb amputation in a majority of patients.

Question 21

What is the clinical interest in TNF at present?

Answer 21

• Neutralizing its biological effects.
• This is achieved through the administration of anti-TNF monoclonal antibodies or soluble forms of the TNF receptor.

Question 22

What is Enbrel?

Answer 22

• Enbrel is an engineered hybrid protein used in the treatment of rheumatoid arthritis.
• It consists of the extracellular domain of the TNF receptor fused to the Fc (constant) region of human IgG.

Question 23

How is Enbrel produced?

Answer 23

Enbrel is produced in a Chinese hamster ovary (CHO) cell line, from which it is extracted as a dimeric soluble protein.