EFFETCS OF THE MAJOR HISTOCOMPATIBILITY COMPLEX
CLASS II (MHC II) ENGAGEMENT AND OF THE MESO-TETRA(4SULFONATOPHENYL)
PORPHYNATE
DERIVATIVES
ON
MELANOMA CELLS
M.A. Costa1, L. Pellerito2, M.T. Musmeci3, G. Barbieri1.
1
Istituto di Biomedicina e Immunologia Molecolare (CNR), Via Ugo La Malfa 153,
90146, Palermo, Italy ; 2Dipartimento di Chimica Inorganica e Analitica and
3
Dipartimento di Ecologia, Università di Palermo, Viale delle Scienze, 90128,
Palermo, Italy.
The extreme resistance of melanoma to the available tumour treatment has
stimulated the investigation of immunotherapy approaches and the
identification of new chemotherapeutic agents. Based on this, we studied the
signalling triggered in melanoma cells by the Major Histocompatibility
Complex (MHC) class II molecules as well as the molecular targets and the
signalling activated by some TPPS derivatives. The melanoma cells often
display a constitutive expression of the MHC class II molecules which is
usually associated with a higher metastatic dissemination. Therefore, in the
aim to understand the intracellular signalling that melanomas use to frustrate
an effective anti-tumour response, we stimulated the melanoma cells with a
specific anti-MHC class II monoclonal antibody (L243) that mimic the class
II interaction with the TCR. Interestingly, in stimulated melanoma cells we
observed an increased localisation of HLA-DR molecules in lipid rafts and
their physical association with the adhesion receptor integrin 1 in these
membrane compartments. FAK and JNK activation as a consequence of the
class II engagement were also reported. Afterwards, we analysed the
proteins localised in exosomes secreted by stimulated melanoma cells and
we observed a lower concentration of the HLA-DR molecules as a
consequence of the class II engagement. Moreover, in the aim to identify
new potential anti-tumour drugs for this aggressive type of cancer, we
studied a new class of porphyrin derivatives and we showed that the
(Bu2Sn)2TPPS and (Bu3Sn)4TPPS compounds induce the death for apoptosis
of melanoma cells. The analysis of the apoptotic pathway activated by these
TPPS derivatives, showed that the protein kinases ERK 1/2, JNK, and p38
are activated in (Bu2Sn)2TPPS 10 µM and (Bu3Sn)4TPPS 1 µM treated
melanoma cells. These results strongly suggested all the three MAP Kinases
are involved in the apoptotic death of treated melanoma cells. Therefore, in
the aim to understand the targets of these compounds we analyzed their
cellular localization taking advantage by the porphyrin fluorescence.
Interestingly, the results of these experiments showed a rapid concentration
of (Bu2Sn)2TPPS and (Bu3Sn)4TPPS in the nucleus and in the nucleoli of
melanoma cells in comparison with TPPS. Moreover, we identified
respectively in 500 nM and in 80 nM, the concentrations of (Bu2Sn)2TPPS
and (Bu3Sn)4TPPS sufficient to significantly reduce the growth of melanoma
cells after only 48 h of treatment. Indeed an outstanding slowdown of cell
growth and loss of cell-cell interactions are evident by in vitro wound repair
assay.