New drug gives hope to skin cancer patients

Scientists have developed a drug that shows promise for treating deadly forms of skin cancer, such as melanoma, which are resistant to existing therapies.

The new compound, SBI-756, targets a specific molecular machine known as the translation initiation complex.

These structures are in every cell and play the critical role of translating messenger RNA (mRNA) into proteins. In cancer cells, the complex is impaired, producing extra protein and providing a growth advantage to tumours.

SBI-756 causes the translation complex to dissociate and inhibit melanoma cell growth.

“A major issue limiting the effectiveness of current melanoma therapies is that tumours become resistant to treatment,” said Ze’ev Ronai from Sanford Burnham Prebys Medical Discovery Institute in the U.S. “Combining drugs that come at a melanoma from different angles may help overcome the problem of drug resistance.”

About 50 per cent of melanomas are caused by mutations in a specific gene called BRAF. Patients with these tumours are commonly prescribed vemurafenib, a BRAF inhibitor that shrinks tumours. However, many patients experience a relapse within weeks, months or years because tumours evolve and become resistant to the drug.

A similar phenomenon is seen in mice, where treatment of BRAF melanomas results in an initial response, but the tumours return in three or four weeks.

The team found that if SBI-756 is co-administered with vemurafenib, the tumours disappeared and did not reoccur. Even in mice with advanced or late-stage BRAF-driven cancer, the reappearance of resistant tumours was slowed by including SBI-756.

These data suggest that SBI-756 provides a significant advantage in overcoming tumour resistance.

Reduce tumour load

In other forms of melanoma, caused by mutations in the genes NRAS and NF1, which are known as unresponsive to BRAF drugs, administering SBI-756 alone significantly lessened the tumour load, the scientists found.

The team is now testing whether combining SBI-756 with existing drugs used for treating these types of melanomas can make the tumours disappear.

“The finding of SBI-756 is also exciting for the possible treatment of diseases other than cancer, such as neurodegenerative diseases, where the activity of the translation initiation complex is reported to be higher,” said Nahum Sonenberg of McGill University.

The study was published in the journal Cancer Research . — PTI

Data that may be helpful:

Important Points:-

• Melanoma, also known as malignant melanoma, is a type of cancer that develops from the pigment-containing cells known as melanocytes.
• Messenger RNA (mRNA) is a large family of RNA molecules that convey genetic information from DNA to the ribosome, where they specify the amino acid sequence of the protein products of gene expression.
• BRAF is a human gene that makes a protein called B-Raf. The gene is also referred to as proto-oncogene B-Raf and v-Raf murine sarcoma viral oncogene homolog B, while the protein is more formally known as serine/threonine-protein kinase B-Raf.

Source :- The Hindu, 27-Nov-2015